Re: 2465B Parametric Freq Measurement Error

Chuck Harris

All members of the 2465 family use interchangeable trigger hybrids.
To remove them, remove the four nuts at the corners of the module.

Tektronix considered them all to be "selected"... which I think meant
they tried them to see if they would work. the "-0X" suffix meant
changes in production usually... stuff like Tek vs Maxtek, or this
or that revision on their fabrication line...

I would suggest that your first attempted fix be to remove the module,
and clean the gold contacts with a Q-tip and IPA.

When you put the module back, seat it with finger pressure, and hold
it there as you finger tighten a pair of nuts on diagonal corners.
Then install the other pair of nuts. Tighten the nuts 1/4 turn past
where they just make contact. The tightness doesn't make or improve
electrical contact, so just 1/4 turn past the nut touching the hybrid
when it is touching the PCB.

I use one of the red plastic nutstarters that would be familiar to old
guys that built Heathkits. I wish I could find them new somewhere, but
I have enough to last my lifetime of used.

If cleaning the existing hybrid's contacts makes no improvement, then
swap in a hybrid from a working scope, and that should fix the problem.

-Chuck Harris

Tony Fleming wrote:

Is my Tektronix 2465 DMS using the same part number or do I need a
different one?
Where would I find more information how to perform the replacement?

On Sun, Apr 28, 2019 at 8:43 PM Chuck Harris <> wrote:

The parametric measurements use the trigger hybrid extensively,
and their performance is directly related to how well that hybrid
performs. Some are better than others.

-Chuck Harris wrote:
After successfully calibrating my 2465B, it reports "All tests passed"
on start up. The question marks are all gone! My issue is with the
parametric measurement of frequency. When I attempt to measure the
frequency of a sine wave at frequencies higher than 10 MHz, the scope
reports the frequency as 35.62 kHz. Any test frequency above 10 MHz gets
the exact same report, 35.62 kHz. Below 10 MHz, it reports various
incorrect values (i.e. a 4.89 MHz signal is reported as 6.35 MHz). At
about 500 kHz and lower frequencies, the scope reports the correct
frequency. I have replaced the PAL at U975 - no change. Any suggestions?

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