[Central-Electronics] 20A drift, breaking my heart.

[Jim Candela]

Jon,

It would be interesting to put the 20A on a variac to see if a line voltage change caused the shift.

When I tested several old CE 9 Mhz crystals, I did experience sudden changes. 

Also I have been looking for a cheap source of 9.000 Mhz crystals. Maybe look for 3rd overtone CB crystal on the old RC frequency, 26.995 Mhz. There are a bunch on Ebay right now in various holders.

something similar:
http://amfone.net/Amforum/index.php?action=printpage;topic=27466.0


Jim
W5JKO





________________________________
From: k6jek <k6jek at comcast.net>
To: central-electronics at mailman.qth.net
Sent: Tuesday, August 30, 2011 10:29 PM
Subject: [Central-Electronics] 20A drift, breaking my heart.

I was happy for awhile but my hopes were dashed.  This old 20A was drifting a lot, still drifting about 26 Hz every 10 minutes after an hour.  I took it out of the case and propped the chassis up so air could flow underneath.  Voila! It got darned stable. After an hour drift was only 1 Hz in 10 minutes.  Drift after 30 minutecs was only 5 Hz/ten minutes. How about that?

Would just a little air make it  better?  I put the 20A back in the cabinet and put the most insignificant of fans on the outside on the left pointing into the lower left cabinet vent, a 4" 240V fan running on 120.  It worked much better than I expected.  Drift was down to about 3 Hz every 10 minutes after an hour.

Then tonight, while participating in the vintage SSB net it hopped, jumped  60 Hz.  What the heck? 

Normally I'd think this was a faulty cap, one that has a temperature sensitive fault.  But you know those caps surrounding the crystal in the 20A, C86, 87 and 88?  This early model has none of them.

Is it the crystal itself?  Can they do that?

Thanks,

Jon 
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