[time-nuts] HP 10544A Repair

Frank Stellmach frank.stellmach at freenet.de
Sun Feb 28 18:03:45 EST 2016


Hello Nigel ,

I already have done a similar repair on a 10811, described here:

https://www.febo.com/pipermail/time-nuts/2012-January/062228.html

A comparison of the 10811 manual, p. 8-16 and schematic, let me strongly 
assume, that the 10544 has exactly the same type of NTC inside.

This NTC also has 100k @ 25°C, and 9k93k @ 80.0°C, 8k60 @ 84.0°C as the 
max. temperature.

I chose the new NTC from epcos for an exact match of the  R/T curve, and 
it's a precision type, 1% for R25 and B values , very reproducible, 
interchangeable and stable. The sample had been characterised by epcos 
at 25°C and 100°C, so R25 and B are extremely well in the middle of the 
spec, and I have 9 EA left...

Maybe you need one.. if you are located in NL, that would be no problem.

I did not find the 10544 manual, describing the correct procedure to 
correctly trim R4, but I assume you would 'simply' have to find a 
minimum or maximum in frequency, depending on the characteristics of the 
BT cut.

But I also assume that this trimmer is not accessible from outside?
Maybe difficult to trim , in this case.

Frank


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