[Heath] HW-101 VFO - more

[Kenneth G. Gordon]

I am wondering why I am measuring 11.0+ volts at the emitter of the BJT "zener" in my 
working VFO? I just checked it again.

According to the manual, it should be 8.7 VDC.

The manual also states that the voltages were measured with a 20 Kohms/volt meter,while I 
am using a modern DVM, a Fluke 73III.

Although I know that the older meter would have loaded the circuit more than the modern 
one, since that junction is supposed to be, essentially, voltage-regulated, I am suspicious 
now that the BJT in my working VFO is defective.

At the moment, I don't have a working 20 Kohms/volt meter.

Drift in the working VFO seems minimal, but I haven't really measured it yet either.

I am removing the defective VFO today, and will be testing it. Then I'll report back here.

Also, if I end up having to replace that BJT "zener" with a more modern one, there is the 
LM-336-5 which is a precision Zener I was thinking of using, but I am still in the dark as far 
as its temperature stability is concerned.

Has anyone here tried this component?

Ken W7EKB
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://puck.nether.net/pipermail/heath/attachments/20180306/566a13f6/attachment.html>