[time-nuts] OXCO Issues -- Latest

J. L. Trantham jltran at att.net
Sun May 12 07:55:19 EDT 2013


Thanks for the info.  I suspect the piston capacitor is on the oscillator
board, along with the crystal.  I suspect the trim pot is on the oven
assembly.  At least that was the way it was on the OSC 49-38C I opened.  I
did not have the courage to separate the oven control board from the oven
assembly either.  You would need to disconnect two heating coils along with
a TO220 type transistor from the board and assembly.  I suspect the trim pot
adjusts the temperature to be able to find the lowest temp-co point of the
crystal but I do not know.

I would love to hear more about that circuit if anyone has ever 'autopsied'


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Frederick Bray
Sent: Saturday, May 11, 2013 10:43 PM
To: time-nuts at febo.com
Subject: Re: [time-nuts] OXCO Issues -- Latest

Okay,  I thought that perhaps the heating element wasn't working, so I
pulled the oven apart.

In fact, the internal unit was warm and it got hot when I ran it for a
couple minutes w/o the foam around it.  All of the solder connections which
I can see look good.  I am not sure I want to try to remove the internal PC

There are two adjustments visible once it is apart.  One is a trimpot and
the one that you can normally adjust with the case closed appears to be a
piston type capacitor.  It actually appears to be better constructed than I

I'll take a few pictures tomorrow for those who asked.

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