[Collins] 32 s 1 self oscilation

[David Knepper]

Never rule out, as Carl and Dr, Jerry indicate, low grid drive.

I wonder if you two illustrious gentlemen could come up with the correct
R.F. levels on the grids of say the two mixer circuits, the first and second 
drivers,
and the final amplifiers in the KWM-2 and 32S transmitter stages.

Weak drive can cause all kinds of problems as we all know.

Great job, nevertheless, guys with this discussion.

Thanks

David Knepper, W3CRA/W3ST
Collins Radio Association - Join Today
www.collinsra.com
Editor of the Collins Journal
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----- Original Message ----- 
From: "Carl" <km1h at jeremy.mv.com>
To: <geraldj at weather.net>; <collins at mailman.qth.net>
Sent: Saturday, April 21, 2012 8:21 PM
Subject: Re: [Collins] 32 s 1 self oscilation


>
> ----- Original Message ----- 
> From: "Dr. Gerald N. Johnson" <geraldj at weather.net>
> To: <collins at mailman.qth.net>
> Sent: Saturday, April 21, 2012 7:11 PM
> Subject: Re: [Collins] 32 s 1 self oscilation
>
>
>>
>>
>> On 4/21/2012 11:54 AM, Carl wrote:
>>> long with the other suggestions Ive tamed an unruly S1 and others with a
>>> 22
>>> Ohm 1/2W carbon resistor right at the grid pin of V-7 and a 100 Ohm 1/2W
>>> right at at Pin 8&3 with C58 at the tube side and C59 at the other and
>>> both
>>> with very short leads.
>>
>> Those can be most effective at preventing VHF parasitic oscillations at
>> some possible cost of gain on 10 meters.
>
> That is only one of the benefits. It can also tame a stubrorn low 
> frequency
> oscillation or a not perfect neutralization. Very common in many HF
> circuits. Unless a circuit is already drive starved it shouldnt affect 10M
> at all.
>
>
>
>
>>>
>>> For the finals be sure R119/120 and R43/48 havent drifted high and as
>>> long
>>> as you are at it check the cathode resistors.Next install other 100 Ohm
>>> 1/2W
>>> carbon resistors at pin 3 of both tubes with added .01 discs at the far
>>> end
>>> as with V7.
>>
>> On my 32S-1 schematics, R43-48 ARE the cathode resistors of one of the
>> 6146 with R49-54 the cathode resistors of the other 6146. I can't find R
>> 119-120 on the schematic or parts list. I find them in the 32S-3
>> schematic, part of added grid parasitic suppressors not shown in my
>> 32S-1 manual or the 1959 edition of the yellow book.
>
>
> I used the 32S1 schematic on collins.org
>
>
>>>
>>> Why Collins didnt use some of those basic stabilazation components 
>>> across
>>> all S Lines is beyond me.
>>
>> You'll have to ask Warren Amfahr W0WL about that.
>>>
>>> Also dont overlook a gassy 6AH6 or 6CL6 which would likely be running
>>> hotter
>>> than normal.
>>
>> Also tubes with grid emission will counter act the fixed or ALC
>> generated grid bias and draw more current and in pentodes the gain goes
>> up as the plate current goes up.
>
>
> No different in a receiver where it overides the AGC voltage and in 
> extreme
> cases drives the grid positive with severe signal overload and sometimes
> oscillation the result.
> I see this in receivers, transmitters and transceivers on a regular basis.
>
> Carl
> KM1H
>
>
>>>
>> 73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association
>>>
>>>
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