[Collins] KWM-1 neutralization procedure

[AI2Q]

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
>>