[time-nuts] Speaking of 5370s

[Perry Sandeen]

List,

I have four 5370b units.  Two of the three lost the frequency input
channel while I was using it for long term frequency monitoring.  The fourth unit I bought for “parts or not
working” had the same frequency input problem.
 
Do we see a trend here?
 
Verifying that the input switch(s) are bad can be
monitored on TP 2 and TP 4 on the A3 board on the schematic I have but they are
marked TP 2 and TP 3 on the rear view photo of the A3 board on the same sheet Page
8-85.
 
I don’t know how easy or difficult they are to access.  Unless one can verify the continuity from the
input BNC at those test points it may be a bit premature to blame the switches.
 
Also on the A3 board are a number of TA electrolytic
caps.  If one has to open up there 5370
for repair it would be very wise to replace all caps with new Panasonic,
Nichicon or similar brands better grade of electrolytic caps.  While the TA caps may still work, being 25 to
30 years old they are not nearly the quality of the new modern electrolytics
and at some point they are going to fail.
 
 Fortunately
both input circuits are identical so it is easier to signal trace.  
 
Unfortunately for me this has to be theoretical as
my entire lot of test equipment is packed for moving and I may not be able to
prove or disprove my hypothesis for months to come.
 
However I’m still of the opinion that every piece
of HP test equipment that is over 15 years old should have all its electrolytics
replaced with the newer versions now available.
 
Besides the three defective 5370’s I have eight
other pieces of failed HP test equipment (several I purchased as non-working) all
which will keep me very busy recapping for a month or so when I get to our
condo.  Mouser will probably be able to
declare an extra dividend.  However, as I’m
72, when I’m finished there is a very high probability that I will never have
to repair them again in my lifetime. 
 
Regards,
 
Perrier