[time-nuts] Problem with HP 8656A 50 Mhz reference oscillator

Scott McGrath scmcgrath at gmail.com
Tue Sep 23 21:27:24 EDT 2008


I am having a problem with the 50 Mhz reference oscillator as it
generates a frequency of 47.5 to 49.995 Mhz depending upon setting of
R110.     Q9 is dissipating excessive power and is hot to the touch

A9 collector bias is at 11.5 instead of the proper 11.0 and emitter
bias is at -.65V.    base is
nominal at 0V  I've checked the components to make sure that values
have not shifted.

 Has anyone seen and fixed simiar behavior as this circuit has the
earmarks of one of HP's trick circuits which depend a precise
relationship between selected components in order to perform normally

- Thanks in advance Scott  N1JIN

PS if someone has a spare A3 board they would like to part with that
would be OK as well.
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