[time-nuts] Opening an Isotemp OCXO

Peter Reilley preilley_454 at comcast.net
Sat Oct 29 09:51:51 EDT 2016

More information;

I added a picture to the dropbox from my Flir IR camera.   The picture 
shows the copper block
that the crystal is attached to running at about 200 F.   In the IR shot 
the copper block is to the
right.    In most of the regular pictures it is toward the bottom of the 
picture.    This is with the
unit (minus the S30 chip) running on 5 volts for more than 10 hours.   
Is that too hot?

While running at 5 volts the current is constant at about 4. amps, no 
cycling.   At 12 volts
it cycled between .9 to .1 amps.   I would not expect cycling for the 
temperature control
of an OCXO.   I would expect a linear temperature control circuit.

I looked at the tantalum capacitor on the bottom of the board.   The 
marking is 39-10.
Does that mean 39 uF and 10 volts?   If so then it must be a 5 volt 
unit.   The capacitor
did not explode at 12 volts.

Dropbox link:


On 10/18/2016 9:11 AM, Peter Reilley wrote:
> I bought an Isotemp OCXO82-59 with a frequency of 10 MHz for a $3 at 
> the MIT flea market.
> As expected it was dead.   It heats up as expected but looking at the 
> output with a scope there
> is nothing.   However looking at the output with a spectrum analyzer I 
> can see a faint 10 MHz
> signal.   It seems that the oscillator is running but the output 
> circuitry is dead.   Reasonable
> assumption?
> Anyway, has anyone had any luck unsoldering the tin case without 
> destroying it?
> Pete.
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