[Collins] 32S-3 advice needed

[Bob McGraw - K4TAX]

I agree with Jerry on this one.  Wholesale replacement of tubes will 
introduce more problems than presently exists.

There is a good voltage chart in the manual as well as a resistance chart. 
Unless you have adequate test equipment and good trouble shooting skills, 
using the shotgun approach to effect a repair is usually problematic and 
likely to be unsuccessful.  Due to age, electrolytics may need to be 
replaced.  Do exercise care and replace with the same capacitance value and 
voltage value.

Take the time using a DVM and measure every resistor.  The value should be 
equal to the specified value or lower.  Never higher!  Typical of 2 watt and 
1 watt carbon resistors is to migrate up in value.  A  second approach is to 
measure voltages on every pin of every tube.  They should be within 10% to 
20%.

I wouldn't worry about the mike and mike gain. Get it working in CW or TUNE 
mode first.  Make sure the power supply voltages are correct as measured at 
the radio.  Remember, with new tubes that fact only guarantees new, but may 
still not be a good tube.


73
Bob, K4TAX
Sparta, TN


----- Original Message ----- 
From: "Dr. Gerald N. Johnson" <geraldj at weather.net>
To: <collins at mailman.qth.net>
Sent: Monday, December 21, 2009 10:49 AM
Subject: Re: [Collins] 32S-3 advice needed


> On Sun, 2009-12-20 at 21:51 -0500, frankshughes at aim.com wrote:
>> Hi,
>> I recently bought a 32S-3 and am trying to get it working.
>>
>> This is the first Collins transmitter I have seen and so I'm taking it
>> slow,
>> following the manual, trying to learn all I can.
>> Might be nothing at all wrong with it, just simple novice errors on my
>> part as I learn (no Elmer
>> available here)
>>
>> Or possibly the problems found so far may be resolved by some repairs
>> that I can do, but I know my limits and will
>> stop if my work yields no results.
>>
>> I have bought a NOS all JAN tube set, so I have a way to try new tubes.
>> I also have bought a capacitor replacement kit (C6, C8, C177, C143,
>> C176, C184, C185) which I will put in
>> soon.
>
> Changing the electrolytics is important. Changing tubes requires
> realignment, you don't need that to do yet.
>>
>> I'm using this manual:
>> 32S-3-_7th-ed-06-69_.pdf
>>
>> I have the unit grounded, a watt meter/SWR connected to the transmit
>> out, and that goes into a 50 ohm dummy load.
>>
>> No other connections on the back panel.
>> Collins SM-2 mic. connected to front panel.
>>
>> SECTION 1
>> Installation
>> 1.3 Initial Checks
>>
>> Result= BIAS adjusts fine
>>
>> SECTION 2
>> Operation
>> 2.1 CW Tuning
>> 2.1.1
>> e.
>> Turn the MIC GAIN control (12) clockwise until the meter needle just
>> moves....
>
> You need several things to work here. First the crystal jumper inside
> has to be connected to the local oscillator (P1 in J7), then there has
> to be a crystal for the band, then the bandswitch contacts need to be
> making, the frequency control switch has to be in trans VFO, and then
> you have to peak the driver tuning.
>>
>> Problem - no meter movement at any MIC GAIN control setting
>>
>> f. Set METER switch to P.A. PLATE position, and adjust P.A. TUNING for
>> minimum plate current.
>>
>> Result=There is a slight dip in the meter when I do this adjustment, OK.
>>
>> g. Place the METER switch to P.A. GRID position and EMISSION switch to
>> LOCK KEY position.
>> Advance the MIC GAIN control slowly until approximately 1/2 scale grid
>> current is indicated on the meter.
>>
>> Problem - no meter movement at any MIC GAIN control setting
>>
>> At this point, I stopped and went to the "Service Instructions"
>> section.
>>
>> It points out that most problems are w/ tubes, and clean the
>> sockets/pins as first steps, before more advanced troubleshooting.
>>
>> Tested all the tubes that could be tested in my TV-10.
>> Could not find any TV-10 configuration info for the OA2, 6U8A, so these
>> were not tested.
>
> You could check the 6U8A as a 6U8 or 6AU8. Suffix letter is not material
> in the tube tester. The OA2 is probably OK if it lights up purplish
> inside with power on the transmitter.
>
>> The 6CL6 shows shorts in TV-10 "short" test positions except 4.
>
> That's probably not good.
>
>> The TV-10 book does not say this is normal, but a new 6CL6 behaves the
>> same, so probably nothing wrong but I don't want to blow up my TV-10 so
>> I did not test this one.
>> The 6146's overload the TV-10 current capacity so I did not test them
>> either.
>>
>> Found one (V10, VOX/ANTI-VOX RECTIFIER) that barely moved the needle
>> for the diode test. (replaced it w/ 5726)
>
> Has no effect on drive level in tune mode.
>>
>> Cleaned all the pins/sockets on all the tubes w/ Hosa Caig DeoxIT
>> F100L.
>>
>> The unit seems to have all the original capacitors, so I'm thinking the
>> next logical step is to replace the caps listed above and check
>> function again.
>>
>> If that has no effect, I suppose I could just put in all new tubes and
>> see what happens.
>
> You don't want to do that. All step in the alignment especially the
> neutralization steps will have to be done.
>>
>> If the electrolytic cap and tube replacement has no effect, I will stop
>> and sent the unit off for further troubleshooting and repairs.
>>
>> What do you think of this approach?
>
> Blanket tube replacement will introduce much more work. Don't do it.
>>
>> Thanks,
>>
>> Frank Hughes
>> KJ4OLL
>> Collins Radio Association member 1654
>>
>>
>
> -- 
> 73, Jerry, K0CQ, Technical Advisor to the CRA
> All content copyright Dr. Gerald N. Johnson, electrical engineer
>
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