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eHam Forums => Amplifiers => Topic started by: N6QWP on August 25, 2018, 11:22:03 AM



Title: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on August 25, 2018, 11:22:03 AM
Sorry, that should read SUBSTITUTES

1)Need to find a substitute panel meter that will fit in the holes and will give proper full scale deflection for voltage and current (not worried about dial markings or offset for Tuning) for a "beater" Collins 30L-1 amplifier.  
Interested to know the specs of the original meter???

2)ALSO: Looking for a replacement power supply transformer.  Anything "close enough" to make it work?  
Required voltages and current ratings of the original???  
(Only need 120vac primary).  
Willing to also add another small transformer-if necessary to get all the required voltages?

3)Has anyone found another ROCKER SWITCH that will fit and work for this amp?

Appreciate any ideas that others might have learned.  Tnx es 73



Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on August 26, 2018, 03:59:16 AM
Meter. The manual says 200 - 0 - 500 microamps, 190 ohms, +/- 2%, 2.5 inches square.%

Transformer. Three windings on ithe secondary.

#1. Filaments, 6.3 volts, center tapped @ 16 amps

#2. High Voltage, feeding a voltage doubler. A note in the handbook for mine says the main winding is 650 volts AC at 0.7 amps

#3. A low voltage winding of about 100 volts, which is half wave rectified, supplying about 12mA for the relay in tx and cut off bias for the tubes in receive.

Power switch. I was able to open up the switch, separate the contacts, carefully burnish them and then fitted a relay to switch the power transformer primary, and another one to provide step start. For some reason, they seem very prone to weld up when the amplifier is run on 240 volts 50Hz.

Hope this helps.

73

G3RZP


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on August 26, 2018, 05:18:51 PM
Thanx G3RZP!  With that info, the next step will be to search for "compatible" replacements that won't break the bank.

I just missed an original power transformer for $30 ;-(.  Ameritron is selling their new transformer from the 811H amp for around $100.  Have to check and see if it is close enough and will provide the necessary voltages?

Since I don't care about the "Tune feature", finding a meter with a 500 uAmp movement will be the next project.  No success so far....any ideas on where to find one?

Still looking for a source of a compatible rocker switch for the on off power replacement (missing as well).

Any other recommendations for inexpensive substitute parts are gratefully requested.  This "beater basketcase parts amp" will be "sacrificially" used to test out OLD AMERICAN 811A TUBES for gassyness and flashovers.  Obviously anything close that will work (and that's cheap) is OK.  Tnx es 73


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on August 27, 2018, 04:46:30 AM
Mine has a rewound power transformer, and is for 240 volts only. Power switches are another problem. A search through Mouser might be the best bet. Or try the Collins Collectors association - although I expect that if it's no longer made, one would pay through the nose. Why did people back in the 1960s start going for the 'avant garde' look instead of sticking with good old fashioned toggle switches? I suppose they didn't expect the gear to still be in use 60 years later. It's easier to keep a 1938 HRO rx going - and looking original - than some of the stuff made ten years ago!

That size meter should be common at flea markets, but look at Fair Radio Sales. Surplus Sales may have one, but their prices are never low.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on August 28, 2018, 07:03:09 AM
G3RZP--Was it really necessary to remove the bandswitch and unsolder all the wires to the coils and capacitors to get at the power switch?


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on August 28, 2018, 07:47:36 AM
It was a major dis-assembly job. Obviously a mechanical design by someone who knew that HE would never have to change the switch!


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: W9GB on August 28, 2018, 08:15:22 AM
Brad -
Obvious you know little about Collins or component suppliers for them.  The Collins Collectors Assoc. (CCA) is a “first stop” — like minded restorers/collectors trying to preserve — and not hack 1960s classics.
The Switch is a classic rocker switch (usually Carling) ...
that was used by every USA mfg. of windows air conditioners in 1950s and 1960s.
Electronics Surplus (Cleveland, OH) has a number of surplus electrical and electronic components.
https://www.electronicsurplus.com/carlingswitch-tlgk6a-4c-b-l-a-switch-rocker-dpst-6a-125v

Quote
Since I don't care about the "Tune feature", finding a meter with a 500 uAmp movement will be the next project.  No success so far....any ideas on where to find one?
For replacement meter, CALL Instrument Meter Specialists (IMS) in Lancaster, California.
Staff can provide a suitable “drop in” meter.. NO Hacking or Drilling required.
https://metersales.com/custommeters

The OEM meter for 30L-1 was supplied by Bartlett Instruments in Ft. Madison, IA
Across the Mississippi River from where I grew up — so I KNOW the firm.  They stopped repair/restoration services of Collins meters about 10 years ago, when their last employees retired.
https://www.bartinst.com

Bartlett provided Collins, per spec, a standard Simpson meter case with a Hoyt movement (New Hampshire).  
https://simpsonelectric.com/products/analog-panel-meters
Hoyt was largest analog meter movement mfg, before Chinese product dumping.
http://www.hoytmeter.com/analog-panel-meters.html

Radio Lab Works restoration of Collins 30L-1
http://www.radiolabworks.com/labworks/30l-1/30l1res.htm

Surplus Sales (Bob Grinnell) purchased signigucant Collins surpkus in 1960s-1980s,
when Collins operated a surplus stoure in Cedar Rapids.
http://www.surplussales.com/Collins/Index.html
Much of that surplus has been sold, but he still has a few items.
http://www.surplussales.com/Collins/Coll30L-1.html


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on August 28, 2018, 09:01:14 AM
W9GB

This 30L-1 is already a "hack job" that was available as a parts rig....heavily corroded and missing key parts.  Looks like it was on a boat.....that sank.

My "project" is not to restore the unrestorable- but to use it as a testing platform for trying out old RCA 811 and 811A tubes that are untested for gas and impending grid shorts and flashovers.....rather than risk a "good amp".

Rather than try to build such a piece of test gear from scratch, it seems much easier to use what is left of this beater amp and adapt it for my purposes using whatever I can scrounge up.

I am glad to know that there are hams out there who are dedicated to preserving "good" old pieces of gear....this just does not happen to be one of those.

I was just able to purchase a power transformer and switch that will work (for my purposes) and am still searching for a meter that has the required movement and will fit in the hole in the panel.  Not much point in purchasing expensive collectable parts....and depriving someone else of hard to acquire replacements.

Since the outcome of this questionable amp (and thus my project) is unknown, I think I am prudent in using it for whatever purpose that I can.  Experimenting is part of ham radio.  Not much of anything would have been of interest to a "collector" anyway.

Thanx for providing information on sources and historical data, I'm sure that it will be of help to someone seeking to rehab one of these back to it's original condition.  73




Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on August 28, 2018, 09:09:50 PM
G3RZP--I still have a question about the secondary high voltage windings on the original transformer.  If it feeds a voltage "doubler" and ends up delivering around 1800-2000 volts at the output of the supply, I don't understand how it could only be 650 volts ac.

Might it be from a winding of 650 vac on either side of a center tap....actually delivering 1300 volts into the voltage "doubler"?  Giving losses  in the circuitry, this would seem to make more sense....to someone who is now confused in theory about such matters.  I seem to have forgotten more than I remember, these days.

I couldn't find any information in the 30L-1 manual that gave explicit voltages.  Can you or someone else please verify what the output of the high voltage winding should be into the diode strings.

Thanx and 73


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: K6AER on August 28, 2018, 09:25:52 PM
Badger Magnetics in Colorado Springs can rewind the transformer for you.

https://www.badgermagnetics.com/custom-transformers/



Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on August 28, 2018, 09:31:52 PM
K6AER--This "beater" parts rig did NOT come with a transformer.  Trying to decipher voltages originally required so that I can find a "comparable substitute" that will be "sacrificial" in the event of extreme flashovers while using it as a test platform to test old gassy tubes.

The question still remains:  What was the actual secondary high voltage winding of the power transformer deliver to the voltage "doubler" so that it will deliver 1700 to 2000 vdc to the tubes?  


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on August 29, 2018, 04:59:09 AM
Firstly, the HV is supposed to be 1800 off load and 1600 under full power. Even that is over the 811A ratings.......plus a very naughty arrangement is the original HV metering. A 4 megohm resistor is connected between the meter switch - which is a phenolic switch generally rated at 350 and certainly no more than 500 volts - and the HV line. So when the meter is not reading the HV, the switch tag is sitting up at HV!  Something like a 270kohm 1/4 watt resistor from the tag to ground would cure that problem. The voltage doubler is a full wave doubler i.e. you have a half wave rectifier producing a positive voltage and another half wave rectifier producing a negative voltage so the two in series give  the high voltage and provide equal loading  to the transformer on each half cycle. Now at 1800 volts  off load, there would be one half of 0.707 times 1800 volts of AC, which means about 630 volts RMS from the transformer. Allow for some drop on load and around 650 RMS appears correct.

For what you are doing, I would be inclined to have one transformer for the HV fed from an external Variac and another to give the power for the filaments and relay. That way, you could use a 750 or 800 volt transformer to check the tubes under no load. For the few cents it would cost, I would change the rectifiers to 1N4508s, which would give a bit more headroom if running higher voltage for testing. You need to check the electrolytics are still good, too.

I would strongly suggest a glitch resistor in the HV line - something like 50 ohms wirewound at 10 or 20 watts. Also two insulating stand offs about 1 inch apart with a single strand of 38AWG wire between them to act as a 3 amp HV fuse in case of shorts. Or you can buy a microwave oven HV fuse, although I think they can be expensive. Don't even think of using a standard 1.25 inch long glass fuse!

The 811A is rated at 1500 volts max in ICAS: at that, the peak plate voltage under drive would be about 2400 volts. The 30L1 1600 volts under load would give about 2500 volts peak. The original plate choke of 40 microhenries looks like 880 ohms of reactance, so has nearly 3 amps peak of RF current in it  at full output on 80m. Another reason why they tell you in the manual not to run full output for more than 30 seconds!


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on August 29, 2018, 07:10:55 AM
Thanx for all of that!  That answers pretty much all of the questions that I have, right now.  I was thrown off by the earlier "transformer's output (at 650vac)….that didn't compute in this old brain.

All of those ideas and "fixes" are great safety precautions!  My biggest concern is trying to protect the transformer in the event of flashovers. An MOV wouldn't hurt, either, I guess.

I know that some of the "new" power supply boards, along with the higher line voltages, can create HV output of around 2000 vdc (with no load) to the tubes.....adding further stress to them and posing additional liabilities.

I won't mind having a higher voltage on these tests....actually will be trying to make sure that whatever tubes I "pass", can handle the highest voltage that they will be exposed to in "real life".

I am very appreciative of the help and time given here.  Very 73




Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KB2WIG on August 29, 2018, 08:11:38 AM


The Peter Dahl 30L-1 replacement specs

P.    115/230
S1            550 VAC   @  0.7A
S2             120 VAC  @ 0.1A
S3                6.3 VAC   @ 11A


And all for only $300+ shipping.

KLC


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on August 29, 2018, 09:18:21 AM
Sounds like a good source.  I see that the filament winding is rated at 11 amps vs the original at 16.  I am assuming that others have used the PD xfmr without any problems, though.  Would a warmer transformer (requiring more cfm cooling) be the result?

For someone rebuilding a nice amplifier, I guess that is one of the options.....since finding good used originals is getting more difficult.  Thanx for that info.

I'm hoping to complete "my project" for less than $200, so that would not be in this budget.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on August 29, 2018, 09:20:22 AM
Since 811As draw 4 amps of filament current, 11 amps seems more than little inadequate for 4 of them. Are Peter Dahl transformers still available after his death some years ago?


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: W9GB on August 29, 2018, 10:30:44 AM
Since 811As draw 4 amps of filament current, 11 amps seems more than little inadequate for 4 of them.

Are Peter Dahl transformers still available after his death some years ago?
YES.
Peter Dahl shutdown his company in December 2007, due to poor health.
Peter Dahl, K0BIT (sk) died in 2011.

Jeff Weinberg, owner of Harbach Electronics (Ohio) acquired the knowledgebase and handled orders for Peter Dahl transformers (2008-2012), used in amateur radio equipment.
https://harbachelectronics.com

In February 2013, Peter Dahl’s database, brand name, and trademarks were acquired by
Hammond Transformers (Guelph, Ontario) from Harbach Electronics.
http://www.pwdahl.com

You may not be aware that in August 2013, Peter Dahl’s original database server failed.
Hammond started a DATA RECOVERY process to save the Peter Dahl knowledgebase.
http://www.pwdahl.com/PWDnews.html

In 2015, Hammond engineers, using their latest manufacturing and production knowledge, went back and “re-freshed” or “redesigned” the HV transformers (Hypersils) for the Alpha 91β , Alpha 99, and the Heathkit SB-220 HF Amplifiers.  
Dennis, N9AD and Mike, K4VJ served as Beta testers of these new designs.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on August 29, 2018, 02:14:53 PM
'9GB,

Tnx for the info. I only ever took passing interest since the shipping cost to the UK would be a problem, especially with import duty and VAT, and even more so with current weak £/$ ratio.

But I still think the 11 amps for the filament winding is insufficient! It needs to be centre tapped, too, for the 30L1.
vy 73

Peter G3RZP


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: K6AER on August 29, 2018, 02:57:53 PM
Transformers supplied for the Alpha amplifier designs were made by:

Tranex Inc

2350 Executive Cir,
 
Colorado Springs, CO 80906

(719) 576-1503


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 03, 2018, 07:24:21 PM
I think that I have decided to use an old TV or stereo amplifier HV power transformer, along with separate filament and bias transformers and adapt this "testing platform" to testing only a single tube at a time.

That way, I hopefully can find old cheap transformers and not risk an expensive one to flashovers during testing of the old 811, 811A tubes.

I am hoping that I can use most of the original 30L-1 circuitry and parts....just downside the available voltage and current to handle one tube at a time.

I just can't justify risking an expensive transformer just to check for gas and flashovers.  I assume that with a 4 amp or better filament supply...and  500-600 volt light duty HV transformer, I can develop enough of the required supply to do an adequate job of testing a single tube?

Using separate transformers, I should also be able to apply the high voltage that is developed incrementally from using a variac in it's primary.

Anyone foresee a problem with using the original power supply capacitor and diode boards with a light duty power transformer to develope the necessary supply to test a single tube at a time?  Any ideas or critiques greatly appreciated.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on September 04, 2018, 12:36:13 AM
There's a reasonable chance that the capacitor board isn't useable with the original caps, as they will probably have dried out with age, although I have electrolytics in use in gear that are over 50 years old. A lot depends on how hot an environment they have worked in.

If you can find an old tube TV transformer giving around 350-0-350 at around 200 mA, that would suffice for one ore even two tubes with a voltage doubler. The original diode string was of 600 piv rectifiers and you could use a string of new 1N5408 1 amp 1kV piv diodes for less than the price of a beer! Plus you wouldn't need thee qualising capacitors.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 04, 2018, 07:41:37 AM
I have already ordered new caps and diodes from China for the old boards for around $13 (220 ufd @450 vdc's and 1N5408's).  Could you please clarify what you were saying about not needing three "qualising" caps?

Heading to a ham swap in a couple of weeks to see what I can find in transformers, meters and power supplies.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KD0REQ on September 04, 2018, 08:06:36 AM
in the old days, when blacksmiths forged semiconductor junctions one by one (well, sorta), rectifiers were rather unmatched. so the best one in a string failed and the rest followed. the workaround was to put 470K resistors and .01 disc caps across every rectifier in parallel.

nowdays, with the precision in wafer production and production, plus the larger size, scads and oodles of rectifiers come out of the cut almost exactly equal. practically you can avoid curve tracing and breakdown testing and parallel RC equalization, and just solder the string of rectifiers together.  and they're pennies apiece instead of one to two bucks.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on September 04, 2018, 11:54:28 AM
It is however advisable to obtain diodes from the same batch - usually that happens if they are on the same bandolier.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 04, 2018, 12:23:20 PM
G3RZP-Still unsure of what you are referring to in your earlier mention of 3 qualising capacitors???  Is that a misspelling?  I can't decipher it.  Thanx


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on September 04, 2018, 02:32:10 PM
You need to talk to the Old Timers at the  local ham club, - that gives you a chance of a power transformer from an old colour TV tube that will do!

Never underestimate the power of scrounging, especially if you are willing to put in some physical effort with an OT's antennas!


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 04, 2018, 03:36:14 PM
I'm pretty good at scrounging.  I've found best sources to be at rare swap meets...and epay as a last resort (if in a hurry).

STILL WANT TO KNOW WHAT YOU WERE REFERRING TO AS "3 QUALISING CAPACITORS"???


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on September 05, 2018, 01:35:02 AM
When you put capacitors in series and apply DC, the voltage is distributed across the capacitors in inverse proportion to the capacitances, so the lowest capacitor gets the higher voltage. When you have a string of diodes in series in a rectifier chain, the PIV across each diode will be determined by the various diode capacities. Plus any spikes on the supply can cause trouble. In the early days of silicon diode usage, it was usual to place a resistor across the each diode as well as a capacitor so that the reverse leakage inequalities and inequalities in diode capacity under reverse conditions was forced to be pretty well equal for each diode. The 30L1 only uses capacitors of 1000pf across each diode, and no resistors. So that's what is meant by 'equalising capacitors'.

By the 1980's, most manufacturers had processes well enough controlled that this became unnecessary, especially with the advent of controlled avalanche diodes, which these days, most rectifiers are. The main point is that although 'mix n'match' may work with diodes from different batches, it may not, so it's always advisable to use diodes from the same manufacturing batch. Diodes from different manufacturers can have different characteristics - an example is the 1N4007 from Motorola, which had a maximum  trr (reverse recovery time) of about 7 to 8 microseconds, allowing it to be used effectively as a PIN diode in an RF switch. Some other makes of 1N4007 - introduced later - the 1N4007 has been around a long time - had a much lower trr. Not a problem in a power supply - even a good thing - but made them useless an RF switch.

You sometimes find capacitors across rectifiers in receivers. Where a broadcast or HiFi receiver is used in an area with fairly high field strength from an AM broadcast station, you can get RF coupled in from the power line and rectified in the power supply leading to the background AM being there all the time, sometimes with a 50 or 60 Hz hum added.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 05, 2018, 10:52:54 AM
OK....got it.  There was no "e" and I couldn't make out what you might have been referring to.  The diodes from China, along with the electrolytics, all seem to be from the same manufacturer, but I have no way to determine if from same production runs.  Seems somewhat likely....guess that I will have to try them.


So, Peter, would you check and replace any of the caps across the "new" diodes on the original supply board?  And when you said "when using the substitute tv xfmr, I could eliminate THREE equalizing caps", which ones were you referring to? (When testing single 811's in the test platform).

Or, would you eliminate the caps altogether and perhaps used resistors?  I notice that the newer replacement boards seem to use that configuration.  I'm sure glad that you have enough understanding of both the 30L-1 and the different power supplies.  Thanx again.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KM1H on September 05, 2018, 11:15:02 AM
Caps havent been needed across modern PS diodes for decades altho they still show up in vintage designs. A single 2000-5000 pf cap of sufficient voltage from the HV output to ground is a good addition for any RF floating around.

A similar cap can be used in SS audio circuits to eliminate the switching harmonics.

My own 811/572B tester is a Dentron 160-10L basket case which can be switched between either voltage requirements. At $50 it was far cheaper than building something.

Carl


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 05, 2018, 03:10:07 PM
Thanx Carl....sounds like what I am trying to accomplish with this old wreck.  Wondering what voltages and available current you are using for 811A's.....and for 572B'S?

Are you using the original supply?  Or, have you adapted something else?  

Are you bringing up the HV gradually, or just letting it go full bore....(after letting the filaments cook for how long?)

I just purchased four more old RCA 811A's and three Cetron 572B's...and still have four old 811's.  All need testing.  Don't want to blow them up unnecessarily.



Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on September 05, 2018, 11:06:44 PM
If your 1N4508s came from the same batch, I wouldn't even bother with the capacitors. I would suggest another RF Choke between the end of the one Collins used and the PSU and then a 0.01mFd 3lV disc ceramic to ground to keep RF away from the electrolytic chain.

Electrolytic caps don't like RF current through them...


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KM1H on September 06, 2018, 07:49:17 AM
That amp originally had 4 811A's and later they switched to 572B's. I configured the PS for a FW doubler or a bridge using a HV switch. A Variac controls the voltage and a separate filament transformer is used. I also use it to regetter those tubes since I deal with so many amps using them.

Carl


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KM1H on September 06, 2018, 04:01:26 PM
BTW, an old original Dahl catalog lists 16A. Sounds like a typo and I hope Hammond is not building them to 11A otherwise a lot of smoke.

The Ameritron xfmr is used with both amps and is one of the best bargains on the planet. Ive used several in projects plus replace in other old amps.

Carl


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 06, 2018, 04:58:36 PM
So in the 160-10L, I deduce that you are using their original transformer with another filament transformer?  Still trying to determine how much voltage you have available to test and getter the 811A's and then the 572B's?

From what I have been reading, the 572B's will require more than the 811A's can handle to properly test them.  Thus my inquiry about whether the transformer is original....or a substitution?  

I understand that the variac will reduce the HV for 811A's-if the voltage available is too high for them.  I read that the original Dentron transformer provided about 2KV (about the same as my original 30L-1 with the Young board)?

Thanx Carl.....would want to verify the Peter Dahl info before going any further with it.  Can contact Ameritron for their info.




Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KM1H on September 06, 2018, 05:45:04 PM
Read post 32 again


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 06, 2018, 06:26:35 PM
OK....was just hoping that you would share with us, what the actual highest voltage is that you are able to develop with your changes?  When chosing a substitute transformer, that will help in my selection.  Thanx


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KM1H on September 07, 2018, 10:21:16 AM
All I did is reconfigure the rectifier circuit so both the 811A and 572B voltages were produced, about 1000 and 2000V at no load but 1500/3000 also works or anything in between. The Variac sets whatever I want down to zero.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 07, 2018, 10:41:08 AM
Thanx Carl--That's what I needed to know.  Now "the Hunt" begins in earnest.  

I read somewhere on these threads, I thought, that the 572B's needed more than 2K to getter and also to stress them a bit?  Something about when substituting the 572B's in a 30L-1, they weren't getting enough voltage (perhaps it was current?).

That was probably more about whether they will actually last longer in a 30L-1.  I guess all we are doing with a test platform is checking for gas and trying to weed out the ones that are obviously bad to eliminate flashovers.

If you have been able to do it successfully at 2K, that's what I was wondering.  As always, your advice is greatly appreciated.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 12, 2018, 07:39:27 AM
****  30L-1 TRANSFORMER PRIMARY WIRES SEEM VERY LIGHT DUTY???  ****

Just had a chance for a closeup inspection of a removed Collins 30L-1 ORIGINAL power transformer.  I was amazed that the AC PRIMARY WIRES appeared almost TINY for handling the amount of current that it does.

Whle they are solid, the diameter is much less than a standard computer power cord.  Anyone familiar with this amp care to make any observations....or explainations?

I seem to remember old TV transformers that had heavier wires (which were stranded)....and they handled lighter loads.

When I search for substitute power transformers, should this be a concern....or are light wires not something to worry about?  Or, is the fact that they are solid and not stranded the reason that the can be so much lighter?

For a transformer that is that size and weight, I expected much heavier wires.

The AC line fuses are 7.5 amp.  It is wired for 117 vac.  What am I missing here?


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on September 12, 2018, 09:12:18 AM
It has two individual 117 volt primaries. Each is switched by one pole of the double pole power switch and each is fused originally at 8 Amps. So the leads don't need to be as thick, and the fuses are the same value for 117 as for 234 volts.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 12, 2018, 09:23:15 AM
G3RZP--Thanx, I was just typing as you replied.  I just noticed that about the dual primaries while reading about the supply online.  That would explain the diameter of the wires, since the load is split between the two....and they could be half the size of a single primary transformer.

That will answer the question about searching for a replacement transformer with a single primary.  One will require thicker primary leads, as I was pondering.

I will also be searching for a heavy duty filament transformer, so that I can control the HV for testing separately with my variac.



Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KM1H on September 12, 2018, 09:35:36 AM
Quote
I read somewhere on these threads, I thought, that the 572B's needed more than 2K to getter and also to stress them a bit?  Something about when substituting the 572B's in a 30L-1, they weren't getting enough voltage (perhaps it was current?).

It is all about current for gettering which is what gets the 572B anodes glowing a bit red.
First of all I dont want any tube arcing over as that all to often destroys it.

Voltages up to about 1200V will not sustain an arc in even a moderately gassy tube so the LV switch position is where I start testing and looking for telltale glows.

In order to regetter a 572B at 2000V or less I use an old 70's HP 0-20V PS for bias (Any variable DC supply will work and one with adjustable current limiting is best) and crank it up until I get a nice red color and let it cook for an hour or more.....I forgot...use a small fan on the glass.

Carl


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 12, 2018, 02:23:16 PM
Thanx again Carl.  Could you, perhaps, for clarification, describe exactly what YOU look for inside the tubes to indicate gas?  Color that might be ok?  Color that definitely indicates impending doom?.....AND WHERE?  (For BOTH 811A and 572B Tubes)

There seems to be some difference of opinion and it would be great if you could clear things up....once and for all.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KM1H on September 12, 2018, 04:06:42 PM
Blue on the glass surface is OK and common with power tubes.

Blue down in the filament to grid area is outgassing. Also often seen in RX tubes that have been run very hot due to leaky paper bypass caps in the AGC line to the grid killing the bias voltage. Those tubes should be tossed.

Purple anywhere is AIR and precedes the white getter. If not too bad it could be absorbed into the anode depending upon the actual gas. At best it is temporary.

Carl


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 12, 2018, 04:35:01 PM
OK....that seems to agree with K5JXH's observations on his website....Just wanted some confirmation.  Thanx

ONE LAST QUESTION, regarding this project, concerns how you get the tubes to draw enough current to start to glow for testing for gas.

I was assuming that I would have to use the entire amplifier circuitry and load up a driven rf signal (from a keyed rig) and load the "test amp" into a dummy load.  Seems like a lot of stress on the driver rig to key it for long periods of time (over an hour?).

Your last reply about a variable bias power supply, seemed to infer that perhaps one could get the tubes to draw enough current by just adjusting that bias voltage (without using the entire amp and tank circuit)?

Are you able to get the "testing platform" (modified hf rf amp) to make the tubes draw enough current to cause the anodes to glow, so that "observable gas glows" can be seen and the tubes can be evaluated--WITHOUT USING THE OUTPUT CIRCUIT INTO A DUMMY LOAD (when driven by a rig)???

That would sure simplify the testing setup and procedure.

Once this is answered, I'll give us all a rest.  Many thanx for all of the great insightful information.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KM1H on September 12, 2018, 05:35:39 PM
What output circuit?  This is just a tube test jig and not an amp. I guess I wasnt clear enough in Post 29.

I use real amps for final testing and returning to the owners.

Quote
Once this is answered, I'll give us all a rest.  Many thanx for all of the great insightful information.

Promise? ;D ::)
Actually I enjoy doing this when there isnt some doofus sniping away >:(

Carl


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 12, 2018, 06:14:24 PM
Thanx Carl--I really enjoy "coming to school" and you are one of the best teachers that I have ever had.  I'm learning more here, than I could ever from ANY other source.

I guess that I am trying to use this old basketcase 30L-1 amp to accomplish BOTH TASKS.  I will install a heavy duty filament supply and use my variac to control how much HV I apply.

So....just to be sure that I get all this, by just varying the bias supply voltage, I can cause the tubes to draw enough current to cause the anode to start to glow....If I keep the HV below 1200 vdc, I can observe the "glows" to determine whether a tube is potentially going to flashover at higher voltage??

I guess I will have to "isolate the tank circuit with some kind of switch ) in/out....so that I can progress after doing the basic test and then proceed with the "loading it up test".

Is there anything else that I should know (Opps, I forgot to promise) when running an amp with an HF driver and into a dummy load, before I accept a tube as "good enough" to pass onto using it in my "good 30L-1"?

"By George, I think I've got it!"



Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 15, 2018, 07:25:42 PM
 
      ********KM1H, CARL********

If you get a chance, could you please confirm that my understanding (as requested for comment, above) of the use of adjusting the bias is ALL that is needed to make the tubes draw enough current to test them for gas.

I just want to be sure that I actually have a good and correct understanding of what you were saying.

I just picked up a power supply at a ham swap meet today, for an old NCX-3.  Except for the correct filament voltage (will need another transformer for that), I think that I can use the power transformer from it along with a voltage doubler (original Collins 30L-1?) to run the tests on one 811A tube at a time.  I think it now delivers about 700 vdc at 200-300 ma.

I also picked up an adjustable power supply (0-50 vdc) that I hope I will be able to use for that bias voltage?

Thanx again, for helping me nurse along this project.  73


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KM1H on September 16, 2018, 08:54:24 AM
Yes.

Back to a cranky lawn tractor and dishwasher


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 16, 2018, 10:49:19 AM
Great Carl--I guess I am finally ready to build up the supply to test the 811A's.

I just noticed that this supply (NCX-3 clone) ALSO has a -80vdc bias output on it.

That will only leave finding a 6.3vac  filament transformer.  If I put a pot inline with the bias voltage, I SHOULD be able to vary BOTH the HV (with the variac) and the bias for the initial gas testing.

Hopefully, here endeth the lesson......(for now ;-)  Vry 73's to all who contributed.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 16, 2018, 02:40:29 PM
OK.....one mo' question (of course ;-)  

I notice that the NCX3 supply has a filament winding of 12.6vac @ 5amps.

Is there any viable way to reduce that voltage in half to 6.3, that will not affect the available current of that winding?

A single 811A needs 4 amps of current at 6.3 vac.  I am assuming that I will need another separate transformer for that...….but it would be much simpler (if some modification to the existing winding were possible) to use that 12.6 vac winding to supply the necessary 6.3 vac @ 4 amps.

I'd love to put two tubes in and wire the filaments in series.....but I fear that the current rating of that winding would not handle two tubes, each drawing 4 amps.

Anyone come up with an alternative solution?


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 16, 2018, 06:08:37 PM
Would adding another tube, WITH FILAMENTS WIRED "IN SERIES" ACTUALLY REDUCE THE VOLTAGE ON EACH TO 6.3 AND WOULD THE AMPS DRAWN "REDUCE OR DOUBLE.....OR REMAIN THE SAME"?= (THE POWER DRAW (AMPS) FROM THE TRANSFORMER)??

Would the 12.6 vac @ 5 amps winding be able to handle TWO 811A TUBES @ 6.3 VAC (4 amps each)???

Is this "THE SOLUTION"?


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on September 17, 2018, 02:29:48 AM
Two (or even 20!) tubes drawing 4 amps each wired in series will still draw only 4 amps. That's how the old tube TV receivers did it with a series heater string. This was common in Europe because getting rid of the mains transformer reduced cost considerably, and allowed the use on DC mains, and a half wave rectifier and big filter capacitors allowed the use of about 180 volts of B+ after filtering.

It had a downside, of course. The mains plugs in the UK 'standardised' as a fused plug with an internal fuse of between 1 and 13amps depending on application and defined live, neutral and earth pins. The power lead from the TV had, in those days, a red covered wire which went to the rectifier and a black, which went to the TV chassis. Red was always connected to the mains Live pin and black to the neutral: this meant that load on supply network had a lot of DC superimposed on it. When popular programmes were on TV and a break came leading to people switching on electric kettles, the extra load in addition to the DC was pushing the distribution transformers to saturation in many places, and they over heated and a number caught fire....usually on a Sunday night, when there were some very popular programmes.

The joys of 1950s and 60s Britain!


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 17, 2018, 07:47:43 AM
One further bit of explanation, please:  Two 811A's with the 6.3 vac filaments wired in series to a 12.6 vac @ 5 amp transformer will each get their required 6.3 volts.

The 5 amps "AVAILABLE" will then be SPLIT BETWEEN THE TWO TUBES? (providing ONLY 2.5 AMPS TO EACH TUBE)???   OR,

Will EACH TUBE BE ABLE TO DRAW THE REQUIRED 4 AMPS????    If so, how????

I'm having trouble seeing how the 5 amps (available) can still provide the TWO tubes with enough current (4 AMPS EACH) to heat up to the required temp.

This old brain keeps giving me visions of a 5 gallon bucket of water trying to fill two 4 gallon buckets.  Probably not a good analogy, but my thought process is hung up there.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: SM5GLC on September 17, 2018, 08:26:28 AM
As the tubes are in series, they draw equal amount of current, i.e. 4A. Voltage is split in half over each tube. Just like two equal resistors in series.
No magic, just basic Ohm's law :D If you have two items in series, the current always be the same, it cannot disappear magically, it is dependant on the sum of resistance. As the current is the same through the tubes, the voltage may vary (due to not perfectly matched filament resistance), and the filament power will vary accordingly.

And a 12V 5A transformer delivers 60W and having a 6V 4A transformer gives only 24W.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 17, 2018, 08:36:41 AM
OK, thanx….

I guess I can see that happening, but I still have an issue of trying to get my mind to accept that a single 5 amp supply can deliver 4 amps to both of the tubes at the same time (without the transformer overheating or each filament getting less).  

I'll accept the premise based on Ohms Law....but I keep getting a vision of a water hose that is split into a Y.  When both are opened, the water flow is cut in half in each leg.  (I guess it is more representative of the voltage than the current).

This is great news, as I can temporarily use the same old power supply, pretty much the way it is.  Will replace the caps and use diodes, but the single transformer should provide what is necessary to run some preliminary gassing tests on those old 811A's.  

I'll still be looking for a separate filament transformer (6.3 volts at 4-5 amps) so that I can independently vary the HV with my variac.....to test one 811A tube at a time.
 
Tnx es 73 all


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 17, 2018, 03:58:50 PM
OK....."The Retard" is back.  Been pondering the above scenario all day and still having trouble making the case that each of the two tubes (when wired in series off of a 12.6 volt 5 amp transformer) is going to be able to get the FULL 4 AMPS OF CURRENT that each tube requires.

I get that the voltage will be halved....providing 6.3 volts to each tube.....AND I GET THAT while the current flow to both tubes might be 4 (or 5 if they are going to get the full measure of what the winding can supply).

Now that we have the correct voltage of 6.3 for each tube.....and that the maximum available current is 5 amps, why do  four 811A tubes "REQUIRE" 16 amps (4 amps each) of filament current when wired in parallel....and two tubes (each still requiring 4 amps INDIVIDUALLY) get away with achieving  their required FULL current from just a 5 amp source????

I know that I am refusing to acknowledge something here, but if two tubes, no matter how they are accessing their REQUIRED CURRENT TO FULLY PERFORM, still require 4 amps each....4 amps plus 4 amps  equals 8 amps.  

I just can't get how one can get TWO tubes their FULL 4 amps each from a 5 amp transformer.  I CAN SEE HOW ONLY 5 AMPS IS AVAILABLE....BUT, it seems that they would have to split that available current AND RUN AT LESS THAN WHAT THEY REQUIRE?????

Sorry to belabor the point so much.....I just wish somebody could get my stubborn brain into the correct "mode".  I'll give it up if nobody can clear this point up....but I sure would like to "get it" instead of just having to accept it ;-(


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: W9IQ on September 17, 2018, 04:42:10 PM
In a series circuit, the current through all devices is the same. When these are resistive devices like filaments, the current through the devices is the voltage of the supply divided by the total resistance of all of the filaments (I=E/R). Since a single filament needs draws 4 amps at 6.3 volts, its resistance is 1.575 ohms (I=E/R=6.3 volts/4 amps). Two of these in series (since resistances add when in series) is 3.15 ohms.

Now when you use a 12.6 volt transformer, the current is 4 amps (I=E/R=12.6 volts / 3.16 ohms). The short version of this is that if you double the supply voltage and place two of the filaments in series, the current through each is the same as a 6.3 volt supply and a single tube.

- Glenn W9IQ


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 17, 2018, 06:52:37 PM
Thanx Glenn--I surrender!  Just confirm for me that the previous posting that stated that "2...OR even 20" would all get the required 4 amps from that same small filament winding was correct.
If that is, in fact true, I will accept defeat and go back to the books.   Tnx es 73


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 17, 2018, 08:27:53 PM
Oops.....I think I see what threw me waaay off the track.  I understand two tubes at 12.6 each getting 6.3 and the current will still be the same if the two are in series.

What I thought I read, was the comment about "even 20" would all receive 4 amps?  Upon re-reading, I don't think it applied to the same supply of only 12.6 volts.....AT LEAST I HOPE NOT!

Perhaps that is what has stalled my comprehension of this issue.

If G3RZP can kindly straighten me out on this issue, I think that this issue will finally be understood?
....


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on September 18, 2018, 06:02:30 AM
20 tubes would require 126 volts. You have to apply Kirchoff's law about the current adding up around the circuit to zero. In the days of analogue repeaters on submarine cables, they used to feed quite high voltages in from a constant current supply: each repeater drew substantially the same current and so ended up with right volts across it. Bear in mind that TAT1, the first Transatlantic Telephone cable used tubes with over 51 repeaters at 69km intervals: it opened in 1956. Incidentally, my father in law worked at the HF station at Rugby: he told me that when TAT1 opened they took some 18 HF ISB telephone channels out as no longer needed and had them back again within three weeks because of the increased demand!

Some of the signalling systems on railways in the UK also use constant current sources with things in series.

Many of 'All American Five' tube radio used series heater strings: a 12K8, a 12K7, a 12Q7, a 35Z5 and a 50L6, all with 0.15 amp heaters, adding up to 112 volts and connected across the 115 volts supply of those days. That saved the cost of a mains transformer....


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KM1H on September 18, 2018, 07:24:03 AM
Quote
Many of 'All American Five' tube radio used series heater strings: a 12K8, a 12K7, a 12Q7, a 35Z5 and a 50L6, all with 0.15 amp heaters, adding up to 112 volts and connected across the 115 volts supply of those days. That saved the cost of a mains transformer....

You really are showing your age Peter!  The more common octals are the 12SA7, 12SK7, 12SQ7, 35Z5, 50L6. These days a 45Z5 is a popular swap for the higher line voltages.

Carl


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on September 18, 2018, 09:31:33 AM
Thanx Guys!  Finally got through to what is left of this old brain matter.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on September 19, 2018, 04:17:07 AM
Carl,

Of course I'm showing my age! I went to my first FD in 1948 in a stroller at the age of 13 months.....Definitely brought up in ham radio.

The 12SA7- 12SK7 -12SQ7 line up never caught on over here - standard before miniature valves was 12K8 - 12K7 - 12Q7 - 50L6 - 35Z4, with a dropper resistance to allow for 240 volt mains. A very few radios used line cords..

73

Peter G3RZP


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KM1H on September 19, 2018, 09:24:49 AM
I wasnt aware of that lineup in the UK Peter.

By '52 (born in 40) I was crawling around local town dumps and tossing discarded radios into bicycle paper delivery bags and side baskets and building non ham specific magazine projects and by 54 had a AA5 style 5 tube regen operating. By 55 I knew enough CW and entry level theory to pass the Novice the first time and built a 6AG7-6L6G TX for 80/40 plus PS.

Before the AA5 the 30's AC/DC sets used curtain burner line cords. I have several in the collection for display only! ;D

Carl


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on November 16, 2018, 07:36:12 PM
Just purchased a 0-500 uA Russian meter that is supposed to fit the hole in the 30L-1 as a replacement for $17 (on epay).  The scale reads that....just hope that it is the actual current rating.

Not holding out too much hope, but might work temporarily and the price is right.  Figured it might work "close enough" for reading the voltage and current (by multiplying the readings by 2 and by 4).  At least, I hope that I should get some useful relative readings for tuning.

Not using the Collins quick tuning procedure that uses the down reading part of the scale, so crossing my fingers and hoping for the best.

Been searching for a real Collins replacement meter....but haven't been able to find a "deal" that I'd want for an old amplifier "abortion".  This old project is loafing along at a snail's pace....but getting closer all the time.

Found (what I think is) an old  Heathkit cabinet that "almost fits" and looks pretty close to the original Collins.  Need a couple more pieces of metal work to safely button up the unit, and it should be ready to test out to see if it will perform as a good "final" test platform for the old 811 and 572 tubes.....maybe even get on the air at some point?

Love tinkering with this old gear.  Have a couple of nice 30L-1's and this "basketcase of the living dead".  It's amazing what a little determination and some insightful and knowledgeable help from this forum can accomplish.  "Never abandon the really good old gear".....just keep it keepin on....even if it's with bandaids and chewing gum.

Thanx to all that helped and very 73's.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: G3RZP on November 17, 2018, 12:35:33 AM
If you open up the meter and can get to the rear hairspring, you may be able to move the part it is attached to such the that meter with zero current is offset up the scale, thus giving you the equivalent of the Collins meter. You could then make a new scale from thin card or even paper stuck over the original. Relatively easy to do with a computer - in the old days, we used a draughtsman's springbow and Indian ink!


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N2EY on November 17, 2018, 07:59:47 AM
Bear in mind that TAT1, the first Transatlantic Telephone cable used tubes with over 51 repeaters at 69km intervals: it opened in 1956. Incidentally, my father in law worked at the HF station at Rugby: he told me that when TAT1 opened they took some 18 HF ISB telephone channels out as no longer needed and had them back again within three weeks because of the increased demand!

There are documentaries about TAT1 and successors on youtube:

https://www.youtube.com/watch?v=QVRL4UcT1sQ

https://www.youtube.com/watch?v=qOg3aWwE_a0


Many of 'All American Five' tube radio used series heater strings: a 12K8, a 12K7, a 12Q7, a 35Z5 and a 50L6, all with 0.15 amp heaters, adding up to 112 volts and connected across the 115 volts supply of those days. That saved the cost of a mains transformer....

Yes - also reduced the size and weight, which brought additional savings in storage and shipment.

In addition, properly-designed transformerless radios could be used on 100Hz, 60 Hz, 50 Hz, 25 Hz and DC mains without modification.

73 de Jim, N2EY


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on November 18, 2018, 07:33:01 AM
G3RZP-Tnx


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: KM1H on November 18, 2018, 08:09:36 AM
Good information as always Peter.

Carl


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: W1QJ on November 20, 2018, 05:45:36 AM
If you open up the meter and can get to the rear hairspring, you may be able to move the part it is attached to such the that meter with zero current is offset up the scale, thus giving you the equivalent of the Collins meter. You could then make a new scale from thin card or even paper stuck over the original. Relatively easy to do with a computer - in the old days, we used a draughtsman's springbow and Indian ink!

Pretty much what I do when I make up my clone Kenwood TL-922 Ip meters.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on December 05, 2018, 01:53:12 PM
Well, the 0-500uA meter that I ordered from Russia just arrived.  While the four holes for the mounting screws are a bit too small, with a bit of drilling them out, it'll be a perfect fit.

The 0-500 scale will be easy to multiply for voltage and current.....if the scale readings are close.  Guess that will depend upon the internal resistance of this meter.  

Crossing fingers, but in actuality, the meter will only be used for reference.  Will be using an external power swr meter to tune up the amp if it ever gets to the point of functioning in that capacity once again.

Doesn't look like it can be taken apart very easily to move the zeroing resting point or to replace the meter face, but that is not of concern.  Looks great!  (And the price was right!).

Since this whole project is just a "Collection of Close", it is continuing on.  Still need metal work, cages and various other parts, but since the goal is to get this "working" for Very Little investment, am well on the way.

With a few more parts and getting it to the point where it can be safely buttoned up (without worrying about electrocuting myself), I hope to be able to run some tests on old 811's before too long.


Title: RE: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?
Post by: N6QWP on December 05, 2018, 06:01:51 PM
Actually had to "drag" the holes for the four mounting screws on the meter, out with a drill bit....about 1/16' to 1/8".  Meter now fits perfectly and the holes do not show outside the meter.  The diameter of the meter hole itself was fine.

I found an original Collins 30L-1 meter for $50, but figured that, since this was an experiment, would wait and see if this Russian meter would fit.  Happily, it does and should work just fine for what I need.

With the "Heathkit" cabinet and the Russian meter, it now looks pretty presentable....very close to original.  At least, it now looks professional and not the "hackjob" that it really is.  Now on to searching for the missing chassis metalwork pieces so that it will be rigid, rf tight, safe and "semi- complete".

PS--After all this, I would DEFINITELY NOT recommend anyone else trying to "resurrect" a basketcase 30L-1.  Finding the necessary pieces is waaaay too time consuming and costly if trying to bring one of these amps back to "original".

Howsomever, if you are a bit "out there", have nothing but time to kill, and "enjoy the hunt"....it definitely is an interesting endeavor....at least if NOT too concerned with anything other that it "perhaps working".

Hopefully, I will still end up with something better than a similarly priced "homebrew backyard" project amp.  At least the basic chassis, panel and layout is already done....and it will look like a "real amp".