[Collins] Thank you all, and a request for advice

[kwylow zinjanthropus]

'lo Lorin and congradulations:
 
Can you tell us what the repair part was? Was it stock or a non-stock replacement fitted to the task? Thanks. Cal, N6KYR. 

LorinH@aol.com wrote:
Dear friends,

I am writing to thank you all for your caring and helpful emails two weeks 
ago when the L403 choke split in my KWS-1 (SN # 743). I have found a 
replacement choke for the 'long haul' and have also successfully epoxied the old one for 
the short. I ma very grateful to you all. The KWS-1 is now up and running 
beautifully (after nearly 4 solid months of often non-stop work), thanks to the 
absolutely extraordinary and devoted mentorship of Tony, K1KP. ( We 
exchanged no less than 150 emails). 

On another front there is a loud hum in my 75A-4 (60Hz? - it is a low 
'b-natural' on the musical scale). 75A-4 SN # is around 3745 (I cannot recall the 
exact number at the moment - early set-in Alzheimers). The hum does not lessen 
when either the Audio or RF gain are turned down, even to 
"0" but may lessen somewhat when the RF gain is turned up from 85% to 100%. 
It does not attenuate when Selectivity is set to an empty mechanical crystal 
socket. It is there with speaker and/or headset. 

I have replaced all of the Black Beauties, electrolytic and B+ caps (except 
the 40/40/40 can, for which I own a replacement) and some other traditionally 
suspect "deadly" postage stamp and other caps (some are too beautiful to 
change)! and have checked the grounds of most tubes sockets. There is a possibly 
related buzz coming from one of the transformers (I haven't isolated it yet) 
even with no speaker attached.

I have not yet changed the 2 wire line cord to three wire, as I do not fully 
remember the best line polarity to assure when placing the two "hot" wires. I 
do remember there is a series of reflector posts about that.

The hum became suddenly very loud after I casually retuned the crystal slugs 
for 11, 10L and 10H (these bands have been dead on this A-4 for the past 42 
years during which I have owned the receiver [and also the KWS-1]). I just 
thought there wasn't much activity on 10 meters! A true alignment will be performed 
as soon as an eBay purchased signal generator arrives.

Any ideas where I should begin my search to eliminate the hum? I am very 
grateful for any help you might offer. 

Take care, and thanks again for the wonderful replies to my request for choke 
assistance (is that a Heimlich maneuver?). This is a beautiful community.

Best always.

Lorin

WA1PGB

Lorin Hollander 
Cape Jellison Road
Stockton Springs, Maine 04981
Sponsored by the Collins Radio Association
http://www.collinsra.com

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