Re: Tek 2467B

Chuck Harris
 

How many people would simply slap a calibration sticker
on a scope and charge for the calibration?

Using yourself as the minimum standard by which all
technicians, and calibration shops, operate is rather
fallacious.

That most of theses scopes haven't been in the hands
of cal lab for decades makes it even more likely that
the calibration constants are not worthy of saving.

Sure, some of the values may be right on, but which
are those? Which are wrong? You really can't tell
until you calibrate the scope.

How many of the guys on this group have replaced a
vertical attenuator, vertical hybrid, trigger hybrid,
a couple of 10K precision resistors on an A5 board,
a tripler, or perhaps even an entire EHV power supply
board and never once thought about doing a calibration?

Show of hands?

-Chuck Harris

Michael A. Terrell wrote:

How many people would calibrate a scope, before verifying the scope didn't have bad caps? The S/H cap would be the least likely to fail, compared to the average lifetime of the electrolytics. Also, most of the scopes ending up in private hands haven't been in a cal lab for years or even decades so recapping the electrolytics would return it to the condition it should have been in at the last calibration. At least, anything I repaired would have been done this way.

Leakage around the S/H circuit's capacitor could be affected by contamination on the circuit board, as well. A good cleaning should always be part of testing and calibrating very high impedance circuits, as you well know. :)

I too, have worked in electronics for decades. Over five of them including at the factory on systems that were only allowed a 1.5 mV error in a system with a 0 to 5V output in a complex AGC circuit comprised of 14 Op-Amps. One of these boards was part of a kU band communications system for the International Space Station.


Michael A. Terrell

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