[time-nuts] HP 5370A Frequency counter Problem(s)

[John Miles]

It's normal for those last few digits to bounce around when measuring
frequency.  The shorter the gate time, the less-consistent the LSDs will be.
How do the tolerances compare to what's in the manual's self-check
procedures?  You'll note that they don't tell you to expect 10.000 000 000
MHz, but 10.000 000 0XX MHz.

The important things to look at with a 5370 are: 1) verify that the trigger
levels are 0.00 +/- 0.01 with the controls set to PRESET; 2) verify that the
+T.I. ONLY interval is within 1 ns of 100.0 ns; and 3) verify that the
jitter when measuring its own clock reference is less than 100 ps (all of
the ones I have seen are under 50.)  If all of that is OK, then chances are
everything else will work properly including frequency measurement.

I've found that many of them need their front-panel input assembly taken
apart and the switches carefully cleaned/lubed.  That alone may clear up a
lot of flakiness.  There have also been some reports of poorly-seated ROMs,
and/or socket contact problems.

-- john, KE5FX


>
> I got a HP 5370A off of Ebay and although it looks terrible I thought it
> would probably work OK.
> But it doesn't :-(  I downloaded the manual and have yet to print it out.
>
> Question;
> When doing a self check by feeding the 10 MHz from the back into the
> counter it counts cycles OK
> but the last 3 or 4 digits are erratic. I am starting to do as much
> alignment as I can but am
> wondering if this is a known problem and if a cure is known.
>
> Anyway I think I paid too much for this box of problems but will
> continue to try to repair.
>
> Any suggestions (on repair only) is appreciated
>
> Bill K7NOM
>