[Collins] 30K-1 on the air

[David Knepper]

Today,  serial number 12 was fired up on AM and it worked great.  Audio =
reports were excellent and the signal was 10db stronger than the 32V-2.  =
Initial contact was with Glen, WA3GPE, Tony, N3HFB and Tony, WA3GKX.  =
Glen who owns a KW-1 and I will have to get on the air which will be a =
rather unique QSO, using his KW-1 and my 30K-1.  Glenn lives just about =
30 miles from the Collins Radio Center.

My audio problem was traced to a completed shorted 4700 pf mica =
capacitor at 500 WV across the secondary of the audio input transformer =
going to the grids of the 75TH.

Never trust those old micas as I discovered again.  Once I installed a a =
ceramic rated at 1,000 volts, the audio drive to the grids of the 75TH =
tubes was restored.
How I found this bad mica was to compare the audio on the 75TH tubes =
with the audio output from the 6B4 driver tube.  Rather than using a =
scope, I used a pair of headphones and a .01 blocking capacitor - the =
old fashioned way for checking audio loss.  With the D-104 on the floor =
and the headsets connected to the grids of the 75TH tubes, I could hear =
a pin drop - lots of audio.

I wonder how many years this 30K-1 was silent.  I know that I had it for =
6 years and the previous owner who lives about 120 miles north of me =
bought it from a ham in Florida. =20

Now it on to serial number 26 which should be on the air next spring, =
next to serial number 12.  These units were made in 1948 which makes =
them almost as old as I am!

Thanks
David Knepper - W3ST
Secretary to the Collins Radio Association (CRA)
Publisher of the Collins Journal
www.collinsra.com
CRA station call - W3CRA


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