Hi Paul. I have a 170A also. It 'was' pretty much a drifter as yours. I did a complete recap (see my review here on eHam). That helped, but then I did what I do with all my boatanchor reaeivers.... Add a small muffin fan.
You can do this easily, and not drill holes, etc. I just use some double-sided tape to stick the fan where it will circulate the air best. I had a local PC repair shop save all the NFG PC power supplies. The 12 VDC fans used in the ps are 'usually' OK.
Make up a simple bridge / cap and tap into the heater of a nearby tube. Runnung the fans at <12 VDC makes them completely inaudable. I use them in my Collins right down to my Lafayettes.....
Just keeping a small airflow help those old parts age a wee bit more gracefully. ha ha
The fans make a HUGE difference in my Drake TR-6 (19 tube room heater)....

ron
N4UE

K6AER.... You misunderstood my comment about building a 'smaller' amp. The 'big' amp has a beautifully crafted (by a retired tool maker) RF deck that is 2X the size of the entire Amp Supply Amp. The power supply for this RF deck is 3' H, 26" W and 21" D. The plate transformer alone weighs > 100 lbs. It could probably power a fair size radio station. (multiple taps available, I use a pretty low voltage one)
This amp works excellent. Steve, remember you waking me up early one Sunday morning to work you on scatter from NJ to my QTH in KY, during the June contest long ago?? ha ha
Yes, my friend, I DO know that the 3-400Z, 3-500Z, and the 3-500Zg are all the same size and from the same family. I have a small collection of these Triodes. Before his passing, I corresponded with Bill Orr on both this 'big', amp and the tubes in general. You should be careful who you insult with your 'better than thy' attitiude! If I wanted that kind of attitude, I would have stayed married!

I don't understand your confusion over the math....
There is a gap of .065" between either the stator or rotor plates. The plates themself are .020" thick. Does that NOT leave .045"? With .020" in between .065", I figger that leaves .045", total. Half of that (on either side of the intervening plate, divided by 2, should give .0225", should it not?

My concern was simply to insure the 'Load' cap would not arc. 'WIK, thanks for the reminder about the 'pitting'. The cap appears new.

BTW, 'AER, your estimate for the capacity of the load cap, is way off. According to the extensive research I have done, I need a cap with up to 250 pf.

Any one out there have a cap with wide spacing at a value of aprox. 20 to 250 pf??? I would love to purchase one.

Thank you for the helpful comments, guys!

ron
N4UE

Hi. I just posted a question on the "Amplifiers" Forum concerning the 'load' capacitor in my current project, a 6 Meter GG amp.

If you have any idea if the cap I have selected (the only one in my collection with the right value, but close spacing) will work or not, please look at that post.

Thank you!!!!

ron
N4UE

Hi. I am in the process of building another, smaller 6 Meter amp. My "big" amp has a pair of 3-500Zg tubes and works great. It's just way too big for my condensed shack. I am modifying an Amp Supply linear. It will use a pair of 3-400Zs, or maybe the 3-500Zs.

I have an extensive junque box. However, my question concerns the 'load' cap in the pi-network. I have a cap with the right value, 10-280 pf. However, I am concerned about the plate spacing.
(the 'tune' cap is the correct value and has nice wide spacing). The 'load' cap has the following measurements:
-spacing between either rotor or stator plates = .065"
-thickness of these plates = .020"
So.... that gives me: .065 - .020 = .045/2 = .0225 air gap. Will this be sufficient, and not break down?
I DO have a transmitting cap of the same value, but it's bigger than a softball!
This amp has a very large Peter Dahl plate transformer and an external HV capacitor bank using oil filled caps. I have the parts to make an internal cap bank, but thought I'd try the oil filled.

My 'big' amp also uses oil filled caps, but it has a vacuum variable for the 'tune' and a nice wide spaced cap for the 'load'.


Thank you in advance!!!

ron
N4UE

MMMMMM, Yummy Humble Pie!!

Yep, I deserve the 'bozo' award for this one.... It seems there were several contributing factors.

#1, and the 'biggie' was my faithful VOM had self destructed itself on the RX1 scale. I discovered this by accident. I had checked the Emitter PASS resistors numerous times. I always got a very low reading, (.05 Ohms is the spec), so I assumed they were OK.
Yep, there's that word "ass-umed". The higher scales were OK, as were the voltage scales.

#2, and I still haven't figgered this out, all 4 of the Emitter PASS resistors were open. How could this happen?

Luckily, I had 4 of the exact resistors in my rather large junk box.

It's up and running just fine. I guess there is a very positive aspect to all the hours I have put in working on this thing:

1. it's good to be humbled
2. I now know how a 723 works
3. I fixed my 'new' Astron.

Yep, bought a very nice RS-50A off of ePay, for an excellent price. It arrived safely and worked well. The only thing wrong was the AC receptable was broken and horribly repaired. In the process of putting in a new receptable (and a REAL fuse holder!), I shorted the + of the filter cap to ground. Yes, the supply was off and unplugged, but the cap was still charged.
Yep, dead supply #2!!! However, having monkeyed around with the 35A, I immediately realized the SCR (or Triac) in the crowbar was shorted. Easy fix this time!

While on this subject, can anyone out there help me to decypher the 'specs' listed in Mouser, etc, for a Triac replacement?
There is NO listing for a SO565J anywhere in the world that I can find. There are a lot of TO-220 type Triacs listed, but the 'specs' don't relate. I suppose this is a common part and just has an Astron # on it. I have a pair coming from Astron, but would be much happier if I could figure out a common replacement.

A HUGE thank you to all and a healthy and happy New Year!!!

Oh, 6 Meters was open, big time, today from here in N. Florida (EM80) to the Chicago area.

ron
N4UE

Del, sure. I use a Marine battery just fine. I have also connected a 'float charger' up to the battery.

When you get your P/S fixed, you can also use it in conjunction with your battery. However, if the P/S is an Astron, go to 'repeater-builder.com' and read about a simple change to the Astron, to protect it if the AC power fails.
Been there! STILL don't have it fixed...

ron
N4UE

Thanks gang!
I have to admit that my voltage reading were probably not as accurate as possible.... So, Used the DVM just now:
The 'bulk' voltage is OK at 24.3 VDC and the supply for the 723 is OK at 30.4 VDC.

I was asked to check from Pad #2 to Pin #3 of the 723.
Both were .973 VDC.
Next, I was asked to check Pin #2 to Pin #3 of the 723.
They should be the same voltage. However, Pin #2 is 1.645 VDC and Pin #3 is .973 VDC. This indicates a problem with the TIP 29?
As I mentioned, this is a new board (that does NOT mean it's good!), and the TIP 29 is resident on the board.
Since I have new TIP 29s, I'm gonna swap it and see......

thanks again!!!

ron
N4UE

Hi Ron, tnx fer the reply....

I measure +25 VDC at all 4 collector pins of the PASS transistors. This is to be expected, since the collectors are connected directly to the main filter cap's + terminal.
Look at my voltage readings...
Pin #10 of the 723 (output) 'should' be at 14.8 VDC.
Mine is only at 2.3 VDC. This voltage is presented to the base of TIP 29. TIP 29 HAS the correct voltage on it's collector , around 30 VDC.
In order for the PASS transistors to get turned on, Pad # 4 is going to have to give the PASS devices MORE than the 1.7 VDC, Right?
Since pin # 10 of the 723 is only at 2.3 VDC, it's not turning on the TIP 29. Therefore, there is only a small voltage showing up at pin # 2 of the 723 (from the emitter of the TIP 29 through R4). The majority of this voltage should appear at Pad #4 and turn on the PASS transistors. I could try to put more DCV on the PASS transistors bases.
I need to determine why both the old board and new board are producing such low voltages at the 723. I can easily 'lift' a pin on the chip since it's in a socket. Everything 'off board' has been eleminated.
I need to take voltage readings right on the board.
I 'suppose' Astron could have sent a defective board, but what are the odds? I carefully discharged the main cap whren I replaced the board. Every time I have replaced the 723, (don't ask! ha ha), I have carefully discharged C1 and C101, both 2200 uf. I used a 100 ohm resistor, then a direct wire.

Any suggestions?

While I put this project on hold for a few hours, I repaired and restored 2 boatanchor receivers and a Heathkit LINEAR P/S... ha ha

thanks!!!!,
ron
N4UE

I hope you all had a Merry Christmas!
I also want to thank all the kind folks that have offered suggestions for solving this problem, ESPECIALLY:
WX7G, N9MXY, and DXZEPP....

Here's an 'update' (if you can call it that)...

First, I have printed and read EVERY topic here in Elmers that contained the word "723" or "Astron"....
Also, I have repeatedly read the great info on "repeater-builder.com".
Before I list the latest voltage readings, I have done the following:

- disconnected the 2200 uf, 16 V cap from across the output, even though I checked if for both capacity and ESR
- looking into the output connector, I measure 4.3K ohms, which should be correct since I'm looking at the resistive voltage divider that inputs into pin #4 of the 723
- completely disconnected the SCR and pulled the Gate lead (location #1) on the Astron board
- as mentioned before, the new board has the TIP 29 ON the board. The original was mounted on the bottom of the case (insulated electrically)
- the PASS transistors I am using (2N5686) are NPNs rated at 300W EACH. This is the highest rated and most $ of the suitable NPNs. The 2N3771 is 'only' good for 150W.
- by the way, the base of the PASS transistors is connected to the Emitter of the TIP 29, not the collector as someone mentioned.
- I have checked the PASS transistors several times with both a VOM and my BK tester. all OK
- I have carefully measured the Emitter resistors for the PASS transistors and they are all exactly the same

Now for the voltage readings:

(all voltage readings taken from Output -) The chassis is NOT grounded, this is the way it should be.

First, on the Astron board;

Pad #1 (SCR) 0 V
Pad #2 (+ output) .75 V
Pad #3 (- output) 0 V
Pad #4 (Base of PASS trans.) 1.7 V
Pad #5 (power for 723 P/S) 22 VAC (normal)
Pad #6 ditto
Pad #7 to filter cap - and negative buss

Next the 723 (several, no difference)

all voltage reading done with a VOM and DVM, same readings

Pin # my readings, Astron schematic
1, 0,0
2, 1.5, 13.1
3, .7, 13.8
4, .5, 7.2
5, 7.2, 7.2
6, 7.2, 7.2
7, 0, 0
8, 0, 0
9, 0, 0
10, 2.3, 14.8  (output)
11, 30, 30
12, 30, 30
13, 3.2, 18.1
14, 0, 0


Yes, I did make a mistake in my original list! Sorry. I left out pin 6, which did have the correct 7.2 V and pin 7 should have read 0 V.

OK, my question is this....
Since I get the same 723 readings with both the original board and the new board, you would think the problem is 'off board'. However, I have completely disconneted the SCR, and lifting pad #4 should have eliminated the PASS transistors. Doing this made NO difference. Again the E resistors are OK. My 2 'bulk' DC voltages are fine, so that eleminates the transformer and filter caps.....

See my frustration?
I suppose it 'could' be a bad board....but with the same symptoms as the original??

Thanks again (!!) guys...
ron
N4UE

To G3RPZ....
Do you know what they call a virgin in England?

Answer... An ugly 3rd grader!

ron
N4UE

Gee, if I wanted to get insulted, I'd go to a Andrew Dice Clay show.......

I DID have a couple of civil replies sent to my e-mail address. I replied to those with the long list of things checked so far.

"Is it plugged in?" WOW!, is it any wonder no youths want to get involved in this 'hobby'...

I was trying to post the minimum # of words here and I would forward the entire info directly to any civil person that had a genuine desire to help a fellow ham.
I have been accused of 'shot gunning', being a dolt, etc.
I have done the following things, ONE AT A TIME, thank you!
After each action, I would turn the PS on, and check voltages. Always, about 1 volt at the output.

- all 4 PASS transistors replaced with new Motorola 2N5686s. It had 4 GE 74s in there. They were OK, but the 2N5686s have higher dissapation ratings.
I even Beta matched a set of 4, with my B K Semiconductor tester.
- disconnected the SCR
- checked the 2200 uf / 16 VDC cap across the output
- replaced the main filter caps. One measured only .68 uf (!!) and it's ESR was > 20 ohms. The other one was fine, but swapped them both. I suspect the bad cap was the reason that my output voltage would drop when my 200 W 2 Meter brick was used.
- checked and replaced the TIP 29 ( I have a bunch and the original tested bad)
- looked at the voltage out of the main filter caps with a 'scope and it's pure DC.

The problem started when the RS-35A was in parallel with a large deep-cycle Marine battery. This fixed my voltage fluctions just fine for a couple of months. The battery was always disconnected from the PS when the station was not in use. It has it's own "FLOAT" charger. The battery was always connected AFTER the PS was 'up'. One night, the AC power went out, while I was on 2 Meters  with the amp. The PS died. This is a known (and fixable) problem. Usually, the spike on pin 4 of the 723 takes it out.

I replaced the 723 FIRST. No diff. Tried another. Ditto. (I was leary of the 723s because I got them stuck in a block of white styrofoam). However, being regulator chips, I doubt they are static sensitive.
I got the following voltages:
Pin #, my reading, Astron's chart
1, na, na
2, 2V, 13.1V
3, 1V, 13.8V
4, .5V, 7.2V
5, 7.2V, 7.2V
7, 7.2V, 7.2V
8,  na, na
9,  na, na
10, 2.5V, 14.8V
11, 30V, 29V
12, 30V, 29V
13, 3.5V, 16.1V
14,  na, na

I removed the 2N3906 on the board. It was OK. I checked every resistor for correct value. Every diode with both the B K and a VOM, nothing amiss. Followed every trace, you name it. Checked all solder connections on the PASS transistors, tightened up the sockets for the PASS transistors.
OK, by this time the board was getting ratty. (the serial # of this PS is 0266, and it's at least 25 years old.) I got it at a yard sale and it's been in every QTH I've had. So, I buy a new regulator board from Astron last week. It now has the TIP 29 'on-board'.
I carefully replaced the board. Double checked everything. Still dead. Yesterday, I took voltage readings on the 723. Same as on the old board. SCR still disconnected, but it should NOT matter.

Again, my bulk voltage at the main filter caps is right on, as is the voltage on the regulator board used to supply the 723. This PS has always had several 12 V muffin fans to keep the heat sink cool.
The fans are completely disconnected.

NOW can you see why I'm stumped??

I called Astron today and both the telephone # and FAX # "have been either disconnected or no longer in use"....

ron
N4UE

n4ue@arrl.net

Hi. Merry Christmas and a safe and Happy New Year to all........

I have a problematic Astron RS-35A. This thing is just flat kicked my a$$!!! I've ben a ham for over 45 years and have a very large collection of radios, test equipment, etc. I have NEVER had a problem fixing anything, including stuff other guys had given up on.
To be honest, it is starting to border on the supernatural. ha ha (almost)
To describe what I have done to try to repair it would take way too much space. And, there's probably a lot of people who could care less.
I'm going to call Astron tomorrow and have someone 'walk me through this', but I kinda doubt they will be able to help.
So, if you think you might be able to help, please e-mail me directly. I will forward my 'history' to this point, and the latest voltage reading as of this AM.

This thing has me stumped. Heck, there's hardly anything in there!

tnx
ron
N4UE

n4ue@arrl.net
or
bonddaleena@aol.com

OK, it's time for my 'dumb question of the week'....

Please bear with me....It's hard to explain this without moving my hands, I am French, after all! ha ha

My boss has a Cisco Model WAP200E "Wireless-G Exterior Access Point" device. It was mounted on a wooden fence and it has a mast-mounted preamp at about 20 feet. It's out in the open and he lives on a small 'hill' here in N. Florida.
He has had constant problems with it. Whomever installed it, mounted it, the DC injector "T" to the preamp, the LV ps, all out in the open. No ground, etc.
We have periods of 'liquid' sunshine, here in the Sunshine State. ha ha
After his latest problem, I inspected the RJ-45 (8 pin modular) connector on the bottom of the unit. This connector is pretty robust and 'appears' to be water-tight. Not only did water run out (!!) but a contact on both the Cisco and RJ-45 plug were missing! not good....
Anyway, I have now mounted everything in a nice water-tight box. 8 foot ground rod right under the box, etc.

My 'problem' is the 'N' connector on top of the Cisco.
It is an 'N' female with a male pin. The coax cable has the correct (matching) connector. Unfortunately, due to space in the box, the coax has to make a tight bend. This causes the center conductor in the coax to 'recede' more than I like. I have improved the situation with a bunch of turns of electrical tape, right at the connector and the coax. This has added enough rigidity to prevent the center conductor from backing out (for now).
What I need is a 90 degree adaptor. I have LOTS of 'N' connectors and adapters, but nothing with this gender configuration.
Here's what I have done:
- looked at RF Parts for a 90 degree adapter with a male end/female pin and female/female (normal) end.
- contacted Cisco to see if they have such an animal or even a cable made with the 90 degree connector.
- used the largest box possible.

BTW, the cable giving me trouble, is about 18" of LMR400. It's stiff. Knowing the temperature extremes here, it's only a matter of time until the cable 'relaxes' and the center conductors 'don't' anymore...
Since there's not a KW involved here, I'll make up some RG-58 etc. But I need this connector.

thanks!!
ron
N4UE

I also had this delimna. Evidently, the 12BZ6 was a LOT more costly than the 6BZ6 (which is one of my favorite tubes). I believe Drake made a running production change to save some $$$.
Kinda like the way they 'cost reduced' the R-4B into the R-4C.....
I have three 4Bs, and one 4C. 'nuf said.....
ron
N4UE

Check "repeater-builder.com" on the WWW. You will find LOTS of excellent info on 723s and Astrons. The issue of RFI is addressed as well as several simple 'fixes' to prevent 723 failure.
I was using my RS-35 paralleled to a large Marine battery when the AC power failed. It took out the 723, evidently this is a common failure.....

regards,

ron
N4UE