[Fwd: Re: [Collins] Re: Where to start?]

Mon, 07 Jan 2002 00:55:14 -0600

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Message-ID: <[email protected]>
Date: Sun, 06 Jan 2002 21:51:40 -0600
From: "Dr. Gerald N. Johnson, electrical engineer" <[email protected]>
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Organization: Gerald N. Johnson
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To: George Roberts <[email protected]>
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Subject: Re: [Collins] Re: Where to start?
References: <[email protected]>
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Cramolin is the old name, Deoxit the new name. Apply in minuscule drops
to the switch contacts.

Zero beat is about 30 dB down the edge of the filter. Use the calibrator
signal in the passband, somewhere about 1 KHz beat note.

There's a prescribe procedure to alignment of the front end. Starts by
setting the trimmers to preset positions on 10m, then peaking the slugs.
Then working down in frequency peaking trimmers for each band. That's
supposed to make it track better. The contacts on the trimmers that need
the Deoxit are underneath the chassis. You'll know the need when a
trimmer doesn't change with rotation.

The AVC is good enough to copy SSB or CW with the RF gain full up. Times
to run reduced RF gain are during thunderstorms and when ssb signals are
a great deal stronger than the background noise, then backing off on the
RF gain helps get rid of the noise between signals. The RF gain control
injects a DC bias into the AVC circuit so kind of sets a threshold.

Black beauties are molded paper capacitors with slightly rounded ends.
Their dielectric of oiled brown kraft paper has always been leaky but
gets worse with age. Orange drops use polyester or polypropylene
dielectric which has very little leakage and has stood up for 35 or 40
years.

Tubes will be in need of replacement, especially the 6BA6 IF tubes.
Replacing and IF/RF tubes will upset alignment.

73, Jerry, K0CQ

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Entire content copyright Dr. Gerald N. Johnson. Reproduction by
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