[time-nuts] Questions about HP 5370B

Paramithiotti, Luciano Paolo S luciano.paramithiotti at hp.com
Tue Sep 14 07:23:30 UTC 2010

 The 10811 after 20 minutes of warmup have to be warm. You can touch physically the oscillator, if it is not warm the oven do not work. The 100Hz off frequency of the oscillator is  more/less the frequency at ambient temperature.
One of the pin of the 10811 have to be at +24 VDC, measure it. If this voltage is present and the case of the oscillator is not warm, replace or repair the 10811.

Luciano P. S. Paramithiotti

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Charles P. Steinmetz
Sent: martedì 14 settembre 2010 9.13
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Questions about HP 5370B

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,


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