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Author Topic: SUBSTITES FOR 30L-1 METER AND POWER TRANSFORMER AND POWER SWITCH?  (Read 4698 times)
N6QWP
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« 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

« Last Edit: August 25, 2018, 11:44:06 AM by N6QWP » Logged
G3RZP
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« Reply #1 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
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N6QWP
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« Reply #2 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
« Last Edit: August 26, 2018, 05:38:05 PM by N6QWP » Logged
G3RZP
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« Reply #3 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.
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N6QWP
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« Reply #4 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?
« Last Edit: August 28, 2018, 07:15:42 AM by N6QWP » Logged
G3RZP
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« Reply #5 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!
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W9GB
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« Reply #6 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
« Last Edit: August 28, 2018, 08:37:57 AM by W9GB » Logged
N6QWP
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« Reply #7 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


« Last Edit: August 28, 2018, 09:19:41 AM by N6QWP » Logged
N6QWP
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« Reply #8 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
« Last Edit: August 28, 2018, 09:27:38 PM by N6QWP » Logged
K6AER
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« Reply #9 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/

« Last Edit: August 28, 2018, 09:31:15 PM by K6AER » Logged
N6QWP
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« Reply #10 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?  
« Last Edit: August 28, 2018, 09:52:38 PM by N6QWP » Logged
G3RZP
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« Reply #11 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!
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N6QWP
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« Reply #12 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


« Last Edit: August 29, 2018, 07:22:51 AM by N6QWP » Logged
KB2WIG
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« Reply #13 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
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EXTRALight  1/3 less WPM than a Real EXTRA
N6QWP
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« Reply #14 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.
« Last Edit: August 29, 2018, 09:27:45 AM by N6QWP » Logged
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