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Author Topic: Collins 32S-1 issue  (Read 25371 times)
KH6VP
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« Reply #30 on: September 17, 2015, 11:18:25 AM »

...and I did clean the contacts as much as I could. Couldn't get the metal covers off. Dont know how. Anyone can suggest a way? Thanks.
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WB4SPT
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« Reply #31 on: September 17, 2015, 11:44:53 AM »

VCO looks ok.

V5 pin 2 needs to have a 3MHz signal.   Did you scan that low?  If its not there, this points to the 1st mixed stage at V4 or even the tone oscillator V11.  Seems the issue is way before the carrier RF stages. 
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KH6VP
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« Reply #32 on: September 18, 2015, 10:14:54 AM »

Well, I did find where the problem is.

At the right side of C5, capacitor dc blocking of V1B, pin 6, there is the 1.3KHz tone (seen with the oscilloscope). Call this test point 1.
At the dc blocking capacitor 0.47uF, of V2A, pin 8 (Cathode follower) there is nothing. The tone should come here.
I noticed the diagram is different to the schematic; why? Collins has service bulletin 4A, which has a different circuit. There is no more +88V there.

Nevertheless, I couldn't find what is the problem is.

I also noticed that the function switch also goes here (via a 10Ohm to V2A pin 9; Pin 9 also goes to a 220KO to ground). This switch has many wafers and I can not take it apart to see if there is a problem. I did clean the contacts with contact cleaner (carefully).

I am giving up.
Thanks to all that helped. It is appreciated.
Peter
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KH6VP
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« Reply #33 on: September 18, 2015, 10:31:48 AM »

Just a thought.

I am using a KWM-2 (which transmits fine) with a power supply, which was expressly built for the kwm2. It is not a Collins 516F-2. It is designed for both 110V and 220V.

Is there is difference between the connector pinout between the kwm-2 and the 32S-1?
I did measure the HV and MV and Bias on the 32S-1 and they were OK. I didn't measure any other values. Just wondering.
Peter

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WB4SPT
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« Reply #34 on: September 18, 2015, 11:08:05 AM »

Well, I did find where the problem is.

At the right side of C5, capacitor dc blocking of V1B, pin 6, there is the 1.3KHz tone (seen with the oscilloscope). Call this test point 1.
At the dc blocking capacitor 0.47uF, of V2A, pin 8 (Cathode follower) there is nothing. The tone should come here.
I noticed the diagram is different to the schematic; why? Collins has service bulletin 4A, which has a different circuit. There is no more +88V there.


I think you are very close.  You have shown that the tone generator works.  It basically replaces the mic for the audio signal in TUNE mode.  And you have seen that the audio is gone at the cathode follower stage, just downstream.  Somewhere in-between is the issue.  I'm not familiar with the factory/field mods related.  THere is shown a switch that will suddenly kill all audio, named S14.  If S14 is closed, no audio from either mic or tone generator, and thus no RF output either.
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WD8AJY
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« Reply #35 on: September 18, 2015, 01:26:43 PM »

Check the mic gain control and the switch S14 it should be open when the mic gain is turned up. Bob WD8AJY
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AC2EU
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« Reply #36 on: September 18, 2015, 02:47:46 PM »

no 88v? I'd check the B+ supply for a bad filter cap or dropping resistor which probably supplies some other critical circuits as well.
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WB4SPT
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« Reply #37 on: September 18, 2015, 04:02:37 PM »

I agree too.  V2 pins 1, 8 9 DC voltage should id the guilty, if it's DC issue.  And, the S14 if it's  switch issue.  We are rooting for ya!!
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KH6VP
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« Reply #38 on: September 20, 2015, 04:49:31 AM »

Well, I went at it one more time. I then saw a resistor going from V2, pin 9 to a wafer on the emission  switch. You can see the resistor cut (10ohms, measured at 14ohm) between pin 9 and the top wafer of the emission switch (bottom right). This is not in the schematic. I cut it. Then I saw a signal on the modulator diode. But what the hell is that switch connection for?

Then it dawned on me: this is a 32S-3, which started life as a 32S-1!!!.
As I need a 32S-3 printout to continue, I need to wait till tomorrow to have a printout of the new diagram.
The search continues.....


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WB4SPT
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« Reply #39 on: September 20, 2015, 07:23:05 AM »

Oh.   Let's jump away from the audio for now.  

Reading previous tests, you said 455 is ok before the filter.  Did you ever see the 455kHz after the mechanical filter?  

The -3 keeps the tone oscillator on, but it's used only as a sidetone for CW.  The -3, as you see, adds switching to kill that signal from entering the balanced modulator.
Ultimately, for both radios, is that something very near 455KHz is mixed with the VFO, to get you 3MHz +/-.  That's definately missing from your radio.  I'm now thinking the 455 filtering/switching has an issue (since we now know the audio tone is not needed for RF generation).  

ps.  The mic gain works totally different on the -3, with regards to carrier level.  There is now a 2nd stage to that pot, that affects the dc bias/gain of the carrier drive amp. 
« Last Edit: September 20, 2015, 08:02:17 AM by WB4SPT » Logged
AC2EU
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« Reply #40 on: September 20, 2015, 08:05:41 AM »

This repair is going off the path. What happened with the missing 88V? Why worry about the mods unless they prove to have been done wrong?
focus!
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WB4SPT
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« Reply #41 on: September 20, 2015, 10:28:20 AM »

This repair is going off the path. What happened with the missing 88V? Why worry about the mods unless they prove to have been done wrong?
focus!

The bias for V2 is a lot different between the -1 and -3 variants.  I don't believe the -3 will ever see 88 volts at the cathode. 
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KH6VP
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« Reply #42 on: September 21, 2015, 01:02:25 AM »

....and although this radio is labeled as 32S-1, and someone brought it up to 32S-3, it is missing the extra VOX circuit [VOX time constant].... I would like to find out who actually made these changes......more work tomorrow....
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WB4SPT
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« Reply #43 on: September 21, 2015, 05:06:18 AM »

turning into a Frankenradio.  Shocked That 10 ohm resistor might be what the -3 has for a 33 ohm. 
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AC2EU
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« Reply #44 on: September 21, 2015, 08:15:43 AM »

Was this an Ebay or private sale?
If they represented that radio as "working" when you bought it, you have recourse to the Ebay seller .
An ethical private seller should work with you on this, too, unless it was sold "as is".

At this point it could be just a run of the mill repair, or a butcher's special. Too many unknowns from where I sit.

I buy "as is" equipment from time to time, but I always make sure that I have a pretty good idea of what I'm getting myself into BEFORE the purchase.
Cut wires and missing parts are usually a deal breaker for me...unless it's to be a parts unit.

CAVEAT EMPTOR , guys!
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