[R-390] 8640B help

[W4QG]

Hello All, 

Excuse the off topic post (well, not totally off-topic, I am going
to use the 8640B to align my 390A's). I was wondering 
if there might be someone on the list familuar with the design 
of HP 8640B's who could give me some advice on debugging
a problem. 

Please reply direct.

Thanks!

Paul W4QG