[time-nuts] HP quality

[Jose Camara]

I've had better luck with all the 'broken', 'for parts', 'repair' HP
equipment I scored cheap on eBay. It is a cash-positive hobby, buy broken
for $200, sell working to highest bidder (sometimes 10x). Feels as good as
getting a pound puppy in a good home, you learn a thing or two (often more)
about rf, stable circuits, good design and the easy money to be made on
leaky or dried electrolytic caps.  One repair a week keeps the shrink away.

I have the utmost respect for their RF line, spectrum analyzers, generators.
I once had a 22yr old generator that hasn't been used in years but I
couldn't turn a single pot or trimmer, every voltage, frequency was within
spec.  In fact, there are some newer equipment that seemed to show up faulty
more often, like 34970 acquisition boxes - I never found out if it was due
to the much higher volume of those boxes made (same failure rate times 20x
the number of units made), new assembly plant in a new country with not
fully trained workers, or just poorer design.

A couple of years ago there was an avalanche of cheap equipment on eBay,
lots of company must have closed after the .com bubble, now there are less
bargains, and plenty of professional resellers trying to get 90% of retail
on 15yr old boxes.

One equipment that doesn't seem to get to the 'fixed' bin is the 6812B. Nice
AC power generator - variable amplitude, frequency (aviation 400Hz),
glitches, brown outs, etc. Think of almost an arb with 750VA output.  I've
done the 'close your eyes and replace all MOSFETs' just to get a new set of
blown parts, and then stopped at bringing up the FET board from a lower DC
voltage (60V not 500V). If anyone has worked in one of these, any hints are
welcome.

On the 'bad out of factory' issue, I never saw in HP or Agilent equipment,
but one Sony TV once had 5 pins on the tuner never soldered - the factory
whistle must have sounded after pin 5 and the thing was tested and shipped
the next day. This was a lesser line out of Mexico - two XBRs have been
running for 10+ yrs without a glitch.

Jose


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Geoff Blake
Sent: Sunday, September 11, 2011 1:33 AM
To: time-nuts at febo.com
Subject: Re: [time-nuts] HP quality

>> 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

-- 
###############################################
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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