[time-nuts] Service info for HP/Symmetricom 58502A 10MHz distribution amp?

[John Stone]

Hi,
  I've got an HP/Symmetricom 58502A 10MHz frequency reference
distribution amplifier.  It has two 10MHz signal inputs and it 
auto-switches between inputs if one of them goes down.  

The 58502A had been working fine for the couple of years that I've had it, 
but recently it failed in a strange way where it thinks it has
input signals on both A and B inputs even when no signals are present,
and when when signals _are_ present, they don't make it to the
outputs, even if I tell the controller to hard-select one of the inputs
via SCPI commands over the RS-232 port.  The hardware status lights
display consistently with the erroneous interpretation of input signal state.

The User's Guide which contains only a simple block diagram 
that shows a 2-to-1 switch on the inputs that feeds status to the 
microcontroller, and funnels the active input to the 1-to-12 
output amplification and isolation block.  I'm ready to crack it open
and start poking around now, but I was hoping a time-nut might have 
experience or suggestions with these units and/or a service manual
if such a beast exists.

Cheers,
  John Stone
  johns at ks.uiuc.edu

-- 
NIH Center for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
http://www.ks.uiuc.edu/~johns/           Phone: 217-244-3349
http://www.ks.uiuc.edu/Research/vmd/