[time-nuts] Re: Turning off display on HP 58503 A or B

[va2hdd at ebox.net]

Hi Lon, hello to all members.

In  1995 the art of temperature control was a good bit more advanced, 
and a bi-metal thermostat would not be stable enough These ovens have a 
semiconductor temperature control; so I would suspect a shorted 
transistor.

These failures in OCXO are not that rare, and that is why there are 
thermal safety fuses.  And please don't defeat them !

73 from Claude VA2 HDD

Le 02/06/2022 13:55, K5jv via time-nuts a écrit :
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> I was recently evolved in a discussion about the HP 58503 option 001
> display.  The general idea is that there is some command to tune the
> display on or off.  A few ideas were offered but no one had anything
> except "they heard about it."Â  Â I have found nothing on the subject
> from old HP literature.  Comments would be appreciated.  I am not
> talking about turning the power off to the DC/DC converter.
> 
> On a different subject:Â  A couple of month back I got some strong
> criticism about suggesting that the oven in the Z3801A was a potential
> source of problems.   I just got another Z3801A in for repair.  Same
> symptoms as before;Â  appears to turn on normally but after a while
> goes into holdover and stay there,  same LH flat lines.  Once again
> the problem turned out to be the oven.  It was unusually hot to the
> touch.  Changing the oven solved the problem.  Now my question.  I
> have never opened one of these oven, so have no real idea exactly what
> is inside.  I would  suspect that one of  the oven's thermostats is
> stuck in the "on" position.  Since it is a "double oven",  there could
> be two thermostats?   If these are mechanical contacts, as one might
> expect fro the 1995 era, can they be cleaned or replaced?   Comments
> from anyone who has actually seen inside one of these ovens would be
> appreciated.
> 
> 
> 73 de Lon, K5JV
> 281-795-1335
> 
> 
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