[Collins] 32S-3 IF Coil T9 needed

Sat Mar 25 21:53:42 EDT 2017

Ahah, a later 75S-3B. There is that little IF coil in the cathode 
coupling circuit of the two triodes in the Q-multiplier. Item 180 in the 
picture on page 6-10 of the revision 15 manual dated November 1975 
(probably downloaded from the Collins Collector files or mods.dk). My 
print manuals don't have that part in the circuit. My oldest 75S-3B 
manual is dated October 1963 and came with the receiver I bought as an 
employee in May 1964. I didn't like that manual and rewrote much of the 
text and it came out in October 1964. I didn't think to redo all the 
schematic and voltage chart voltages which had changed because the power 
transformer had a higher output voltage. I should have. Art moved me to 
Texas at the end of the summer and my 75S-3B spent the next year out of 
its case as I learned much about how it worked and improved and adapted 
circuits. It was before the magnetic shield for the mechanical filter 
and I added my own design to reduce the hum modulated noise that the 
magnetic field from the power transformer introduced in the mechanical 
filter. I brought out the IF to a jack on the back and replaced the 
rotary switch on the BFO frequency adjust pot with a pull/push switch so 
I could leave the tunable BFO on the same frequency when I turned it off 
and then back on.

The Collins part number for T9 is 278-2080-010, mfg number 16-144-02. 
Its frequency is 455 kHz.

I know one was found last year. I had an extended discussion with a ham 
(have to dig for his name and call) that was experiencing low receiver 
gain and it proved to be that transformer was faulty. When he found and 
installed a different one the receiver gain met the specification. 
Finding more details will take a while with all the e-mails I have 
received and kept in the past year. The bad transformer had so much loss 
that it absorbed all the gain in the Q-multiplier tube sections.

The serial numbers of all the S-line and KWM-2 were issued in random 
order so its hard to know the vintage of the radio except by finding 
date codes on aluminum electrolytics, original crystals, and original 
tubes. Then there was the change from winged Collins emblem to the meat 
ball emblem, and then adding Rockwell. Style changes Art didn't 
anticipate when he decreed the serial numbers must be issued in random 
order.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.

On 3/25/2017 7:26 PM, Bill Riches wrote:
> Hi Jerry,
>
> I made a mistake - it is a 75-S3B - with a poorly Rev 1.  I have been
> restoring boat anchors for many years and know not to use metal tools on
> slugs.
>
> 73,
>
> Bill
>
> -----Original Message-----
> From: Collins [mailto:collins-bounces at mailman.qth.net] On Behalf Of Dr.
> Gerald N. Johnson
> Sent: Saturday, March 25, 2017 7:08 PM
> To: collins at mailman.qth.net
> Subject: Re: [Collins] 32S-3 IF Coil T9 needed
>
> Can't be. 32S-3 is not a receiver, its a transmitter. In the 75S-3 manual I
> have there is no IF type transformer under the chassis. There is L9 but its
> 1/3 a chassis away from R57 and its above the chassis mounted through a hole
> in the chassis.  There is no T9 in the parts list either. Might be part of a
> modification.
>
> You should never use a metal screwdriver or allen wrench to turn a slug, use
> only plastic driving tools for those parts to keep from breaking the slug
> and locking it.
>
> 73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.
>
> On 3/25/2017 11:35 AM, Bill Riches wrote:
>> I am in need of T9 that does not have a broken or stuck slug for a
>> 32-S3 receiver. It is located under the chassis between R57 (IF gain pot
> and V5.
>> Help!!
>>
>>
>>
>> 73,
>>
>>
>>
>> Bill, WA2DVU
>>
>> Cape May, NJ
>>
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