[time-nuts] Questions about HP 5370B

Charles P. Steinmetz charles_steinmetz at lavabit.com
Tue Sep 14 07:12:48 UTC 2010


A friend just received an HP 5370B that was said to be properly 
working and accurate, and asked my opinion.  I'm not familiar with 
these, so I thought I'd ask the experts.  All we've done so far is 
hook it to a Tbolt that I know is operating properly.

The 5370B took hours (8 or so, which seems like a long time for a 
10811) to drift to a reasonably stable reading, a bit over 100 Hz 
high (which seems like an awful lot for a 10811, even after a trip 
across the country ten years since its last calibration).  The 
front-panel oven indicator is off; I did not notice if it was on when 
we first powered it up.  The 5370B reads its own oscillator within 
spec (< 2 mHz error; spec is +/-5 mHz).  We have not opened it to 
tweak the oscillator (or to verify that the 10811 is, in fact, still present).

Timing seems to work OK, giving the expected 100 nS and 50 nS figures 
when I feed the internal oscillator into the start input, tie start 
to stop (START COM), and switch the trigger phase of the stop channel.

Finally, the external heatsink (left rear) runs pretty darn hot -- 
somewhat warmer than you'd really like to leave your hand on, which 
is WAY warmer than I'd ever design.  Concerning (to me), but not 
completely beyond reason.  I suppose it could be normal for 
these.  It didn't burn down or shut off during the 8 hour warmup.

I appreciate any input from those knowledgeable about the 5370B.

Thank you,

Charles





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