[Collins] KWM-1 neutralization procedure

[Dr. Gerald N. Johnson]

The 32S and the KWM-1 techniques should produce the same settings and 
the same effect, a stable PA and driver. Both try to get the feedback to 
zero, the 32S by measuring leak through with no tube gain and the KWM-1 
technique measuring reverse leak through with no tube gain. When the 
tubes aren't contributing gain the circuits are bilateral and so either 
technique should work fine.

I've come to the conclusion that there was a sloppy draftsman making 
schematics and he wasn't checked closely. I wish we had access to the 
entire collection of component specifications those are what purchasing 
bought by and the components department tested incoming parts by.

73, Jerry, K0CQ

On 5/21/2011 2:59 PM, AI2Q wrote:
> Thank you, Jerry.
>
> Yes, I didn't take too seriousl;y the need for a 60-uA meter!
>
> I think I will try the old tried and true method before tinkering with
> the Collins diode detector and sig gen.
>
> Vy 73, AI2Q, Alex
>
> ----- Original Message ----- From: "Dr. Gerald N. Johnson"
> <geraldj at weather.net>
> To: "AI2Q" <ai2q at roadrunner.com>
> Cc: <collins at mailman.qth.net>
> Sent: Saturday, May 21, 2011 1:53 PM
> Subject: Re: KWM-1 neutralization procedure
>
>
>> That is a good technique. If you leave a path for screen or plate
>> current your dip will not be exact neutralization. You have to
>> disconnect those supply lines from the driver to neutralize it. I'm
>> not so sure about the feedback neutralization. There is a procedure in
>> the KWM-1 manual using signal generator and detector. And on the
>> detector schematic I see the draftsman missed a digit on his Leroy
>> lettering kit and calls for a 60 microamp meter that was never made,
>> better to use a 50 microamp meter, they can be bought without having
>> it made special. Just like the schematic for wattmeters shows a 390
>> microamp meter when it was really 300 microamps.
>>
>> Now compare the KWM-1 manual technique to that in the 32S-1 manual
>> which uses transmitted signal with plate and screen disconnected (and
>> there the driver neutralization will work better with both plate and
>> screen of the driver tube disconnected, opening the screen alone lets
>> there be a little tube gain yet) and then neutralizes the feedback so
>> that plate and grid current dips coincide as you tune the pat plate
>> tuning. Without checking, I think that the transmitter circuits of the
>> KWM-1 and 32S are very similar so the neutralization should work well
>> with either manual technique.
>>
>> 73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.
>>
>> On 5/21/2011 12:16 PM, AI2Q wrote:
>>> What is the best way to neutralize the (a) driver, (b) feedback trimmer,
>>> and (c) PA of my KWM-1?
>>>
>>> My late model KWM-1 has a screen-off slide switch as well as an RCA
>>> phono socket on the chassis for the grid.
>>>
>>> I am used to neutralizing by removing B+ from plates and screens,
>>> applying drive, and adjusting for minimum output on my scope placed
>>> across (a 50-ohm load) after peaking the pi-L network on the 6146s.
>>>
>>> Any help or suggestions appreciated.
>>>
>>> Vy 73, AI2Q, Alex
>>> Member: ARRL, FOC, RSGB, CWops, QRP-L, Antique Wireless Association,
>>> Wide Area Amateur Radio Network
>>> http://home.roadrunner.com/~alexmm
>>>
>
>