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   Home   Help Search  
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Author Topic: Collins 32S-1 issue  (Read 25380 times)
KH6VP
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« Reply #45 on: September 21, 2015, 10:01:32 AM »

I printed the 32S-3 manual only to see that this isn't a 32S3 neither.

I did all the resistance measurements, and found a discrepancy in V1 and V2. V1 pin 9 has about 1MOhm, while it is listed as 150K, and V2, pin 9 has 240K when it is listed as 110K.
I started looking around and saw that V13, although a 6AL5 inserted seems to be neither a 6AL5 nor a OA2 (in the 32S3).

I took a photo of the base. Pins 5 and 7 are not connected while pin 1 connects to pin 6 via a 100K resistor and associated circuitry (what are the little black "diode look a likes" that connect to pin 6?). The V13 is at the top of the photo, corner of the chassis. In the pinout of a OA2, pin 6 is not used and neither it is used in the 6AL5. Could it be used as a convenient soldering point?

I bought a 75S-1 from the seller via ebay [it works fine], and when I went to pick it up, I saw the 32S and asked him if it was also for sale. I asked if it worked and he said yes. Well, it didn't, but this wasn't an ebay sale, so I am not covered.

I contacted the seller and he said it came from Canada and it was not tested before. Tomorrow I will ask him to take it back or replace it.

Here is the pinout of V13, in high resolution, in case someone wants to take a look.


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WB4SPT
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« Reply #46 on: September 21, 2015, 10:35:12 AM »

V13 went solid state with those 2 diodes you spotted.  Overall, probably the least of your worries with this box.  Those yellow film caps look newish also.  Do they have a date code on them?  That might be a clue as to when these mods were made.

I don't have any history with the good vs "bad" mods people have been inclined to make on these radios.  Perhaps someone else knows. 
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KH6VP
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« Reply #47 on: September 21, 2015, 10:57:42 AM »

There was a tube in the socket(6AL5). So it is no longer needed?
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WB4SPT
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« Reply #48 on: September 21, 2015, 11:22:58 AM »

V13 probably not needed.  Did V10 get this same treatment?
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KH6VP
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« Reply #49 on: September 21, 2015, 11:37:58 AM »

No diodes on the V10 base......so probably it is needed.....

Thanks to all those that helped. It's wonderful we can all help each other in trying to fix these old radios....
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KH6VP
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« Reply #50 on: September 22, 2015, 01:09:04 AM »

The seller agreed to take the radio back and look into the problem. It maybe a simple issue. Now I know that V13 is not needed.  It came with it however. I will tell you what's going on when I hear from the seller.
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AC2EU
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« Reply #51 on: September 22, 2015, 07:11:23 AM »

The seller agreed to take the radio back and look into the problem. It maybe a simple issue. Now I know that V13 is not needed.  It came with it however. I will tell you what's going on when I hear from the seller.

According to the block diagram in their manual, V13 is the ALC rectifier, which has nothing to do with the frequency issue anyway.
I'm glad to hear that the seller has agreed to work with you on the problem.
It almost seems that this was a tinkers radio and the experiments went south for him, so he sold the rig. As long as the cutting/changing was not too extreme, it's probably very salvageable.
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KH6VP
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« Reply #52 on: September 22, 2015, 09:51:05 AM »

Before I send the 32S-? to the seller, I took these photos. My background is digital so analog is a little perplexing for me.

The diagram is:



1/ I cut the 10ohm resistor that is going to the switch. It seems to be pulling the signal down. All the photos are with the 10ohm disconnected (if I connect it, no signal comes through)

At point 1 (before the 220K resistor), the audiosignal arrives:


Then at point 2, the signal is still there.



Then at point 3 (at the pin 8 of the cathode follower tube), the signal becomes triangular instead of sine wave??



And finally at point 4, at the beginning of the balanced modulator, the signal gets even worse.




Is this supposed to indicate my problem?

Thanks for any advice.
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WB4SPT
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« Reply #53 on: September 22, 2015, 10:37:36 AM »

I think my post #39 still applies. 
With your comment that this is neither a -1 OR a -3 is going to make this very interesting. 
It is possible this rig was modified to improve CW at the expense of even having SSB still active.  This spurs yet another question.  Does the transmitter work on CW?   

Since MicGain varied audio is NOT used to change the carrier power on the -3, it is of importance to find out if/how that is accomplished on your radio. 
The 33 ohm (your 10 ohm) is supposed to kill audio to that cathode follower in the TUne, and some other modes.   
I'd like to determine if the cathode (pin 7) resistor on V6 is fixed or variable.  Is micgain a two section or a single section pot? And, does 455 exist on both sides of the mechanical filter? 


 
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KH6VP
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« Reply #54 on: September 22, 2015, 10:24:34 PM »

CW mode works. Tried yesterday with a key and saw the audio sine wave get here(point 1).
It does have a double MicGain potentiometer plus the switch on top.
When I place the radio in Tune mode, it does kill the audio. I thought the audio is there to tune or produce CW, so why does the signal disappear when in tune, and better still, how does the radio tune with no sine wave?

After all this, I sure wish it was a simple 32S-1!

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WB4SPT
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« Reply #55 on: September 23, 2015, 05:47:28 AM »

It appears you have more of a -3 than a -1.  That modification took some time, and affected switches, pots, components and wiring.
On a -3, the signal path for CW, Tune, and locked Key modes are very close.  Now, do you actually get 100 watts or so of carrier output with locked key?  If so, that proves most all the carrier freq circuitry works. 

To generate either the locked key or Tune carrier, the tone oscillator is out of the equation.  You do need the 455, from the BFO (not VFO) at the correct point.  Which means Pin 3 of V4.  S8J is responsible for the correct routing of the 455 BFO output. 
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KH6VP
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« Reply #56 on: September 23, 2015, 11:50:22 PM »

When I say CW mode works, I also added that the signal gets to the balanced modulator. There is nothing after that. Nothing in any mode, tune, USB, LSB or CW.

My question is how does the radio tune, when the audio signal, through the switch, gets killed in an -3? It should be allowed to propagate so that one can tune the radio. Like in the -1.

The problem with this radio is that nothing happens to the grid and no tuning is possible. The problem seems to be somewhere around the balanced modulator.

I am sending it back to the seller who will hopefully fix it, or replace it with a working one or give my money back. He sold it to me saying it worked fine. I didn't test it; I bought it on trust.

Peter
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WB4SPT
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« Reply #57 on: September 24, 2015, 06:11:13 AM »


My question is how does the radio tune, when the audio signal, through the switch, gets killed in an -3? It should be allowed to propagate so that one can tune the radio. Like in the -1.


No, its much different.  3.7.1 in the manual explains what the -3 does with the tone.  For CW or tune, the "first" two signals in the path to make RF come from BFO and the VFO.  They mix to form about 3Mhz.  That's where you need to look.  73's.  

ps.  "mix" in the analog world, or at least in this context, is to provide mathematically sum and difference signals.  ie:  VFO + BFO, and VFO - BFO.  Collins filters the difference signal, and the two original oscillators, leaving you with BFO + VFO. 
« Last Edit: September 24, 2015, 06:15:32 AM by WB4SPT » Logged
KH6VP
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« Reply #58 on: January 07, 2016, 03:02:19 AM »

Finally, after almost 6 months, and after the seller repaired the 32S-1[choice was repair, refund or replace], I got it back working fine. Apparently the seller had received this 32S-1 from someone who had started modifying it to a 32S-3, but had never finished the mods. All the mods were reversed to an original 32S-1.
Am happy again. Although it takes getting used to zero-beating it, to match frequency with the 75S-1 receiving frequency.
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