[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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