[time-nuts] HP quality

Geoff Blake melecerties at gmail.com
Sun Sep 11 08:32:57 UTC 2011


>> That is not a unique incident.
>>
>> I'm interested in LASER Interferometry. Attached is a pic I took of an HP
>> 5529A LASER head.
>>
>> (Aside: If anybody is interested, there is a Yahoo Group for LASER
>> Interferometer fans)
>>
>> Note the two leads to CR5 near the top, center of the pic. They go to a
>> feedback photocell and obviously have never been trimmed or soldered.
>>
>> The unit ran fine that for several months before suddenly failing.
>> Soldering the leads fixed the LASER head.
>
> It was not always this way.  Today I stumbled on a 1965 HP 738BR
> Voltmeter Calibrator at my favorite surplus electronics store.  I
> offered $20.00 and it was accepted.
>
> This unit is based on vacuum tubes!  I got it home, plugged it in, and
> it is still in spec on the DC range.  The AC part is not working - I
> suspect the small incandescent lamp that stabilizes the oscillator.
>
> I may end up junking the vacuum tube half.  The other part of the
> instrument, in a separate compartment, has a precision 40 step
> attenuator with a 10^6 / 1 range (300 Volts to 300 uVolts) which I will
> certainly keep.
>
> Best regards,

No please don't junk the valve part, it would be be waste of a lovely
instrument.

However that's not the topic.

I first met a HP 3582 LF SA when it came into the cal lab from a
remote site, just out of warranty. Apart from being out of cal, the
was a brief comment, "intermittent channel 1". We had not seen one
before and being the "guv" I got to play first.

Yes there was an intermittent fault and it seemed vibration sensitive.
After I had figured how to drive it (what's a FFT analyser - what's a
FFT? but I was young then.) I could confirm the fault and I had even
found the diagnostics in the manual.

Running diagnostic 1 I determined that the fault was in IC1 or IC3 and
using diagnostic 2 I narrowed it down to IC1 or IC2, so suspecting a
loose IC1 I put a rather large thumb and pressed - the fault
disappeared  Remove thumb and it was back!

In for a penny, in for a pound, I pulled the chip and yes, even I
could spot the doubled up pin, so I gently straightened it and that
was the cure. Later I was told that the fault was there since
delivery, but they could not afford to spare it at the the time.

(Please note the (IC) names have have been changed to protect my memory.)

Geoff G8GNZ

-- 
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Geoff Blake,   G8GNZ    JO01fq:   Chelmsford,  Essex,  UK
<geoff at palaemon.co.uk>    or   <melecerties at gmail.com>
Using Linux: Ubuntu 11.04 on Intel or Debian on UltraSparc
and even on the NAS.     Avoiding Micro$oft like the plague.
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