[time-nuts] 5370A

Greg Burnett gbusg at comcast.net
Sat Oct 10 15:24:06 UTC 2009


The HP 5370A rear mounted heat-sink typically heats up to around 61 degrees 
C. This is very hot to the touch, so I suspect your unit's temperature is 
normal (unless it's running way hotter than 61 degrees C).

The buzzing transformer might just be due to loose, vibrating laminations. 
You might try tightening the transformer's bolts to see if that reduces the 


P.S. I agree that the rear mounted heat sinks of most other HP equipment run 
significantly cooler. The models that run so hot to the touch are the 
5370A/B, 5359A, and many of the legacy HP pulse generators (from Boblingen 

----- Original Message ----- 
From: "Roy Phillips" <phill.r1 at btinternet.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Saturday, October 10, 2009 4:08 AM
Subject: Re: [time-nuts] 5370A

Hi Joe
I have a similar problem so I would be pleased to hear from you with any
useful information. The basic problem with mine is that the power supply is
suspect - it works, but there is excessive heat, much greater than any other
HP instrument that I have, from the rear mounted heat-sink, this is too hot
to hold your hand on ! There is also a very obvious buzz from the power
transformer, even when it is on "stand-by" - so I guess at worst it could be
shorted turns in the power transformer, or probably better, a faulty bridge
rectifier,or one or more of the large reservoir caps -  this an early model
(1984), so perhaps it is to be suspected. I also think the performance is
not to specification, but I will check-out the perceived problem with PSU
before I investigate this matter.  I am just about to start the
investigation of the prime problem.

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