Re: 2445A calibration

Chuck Harris

Two further points I would like to make:

1) Maxim, you made the same mistake many bright guys have
also made when trying to do a job aimed at wage drones.
You out thought the instructions, instead of following
the instructions.

2) I truly hope that after you finish your calibration you
will return to analyzing the ROM code. It would be very
useful to have a reverse engineered annotated assembly
code listing of the ROM. You may not be the one that fixes
some of the problems in this beast, but your notes may
encourage someone else to try.

I, for one, think a debugged 2465A/B that runs as smoothly as
the original 2465 would be a rare and precious treat to use.

I believe the 2465 family was developed by a "tiger team" of
engineers and programmers. When they finished, and the 2465
was selling smartly, they took their accolades and went on to
management, and to other scopes.

When marketing decided the 2465 needed some more bells and
whistles to remain current and marketable, the tigers weren't
available as a team anymore, so one or two of the former tigers
managed a team of new kids, and let them play.

It's purely conjecture on my part, but I think it is close
to the truth.

-Chuck Harris

Raymond Domp Frank wrote:

On Tue, Oct 16, 2018 at 05:31 PM, Max Vlasov wrote:

I wonder whether this is a MEGA GOTCHA?
I'm just dropping and would like to comment as follows:
As you've found out, your 'scope is a typical Tek product: Clever technical solutions in one place, (sometimes not so clever) idiosyncrasies in other places.
The calibration procedures must be followed strictly, except for a few exceptions where Tek made errors. Sometimes it's not self-evident or clear why something must be done the way the calibration describes.
The descriptions contain a trap here and there: Unless you very strictly read and follow the text, you'll have problems. One of the gotchas are instances where you are told to connect a "50 Ohm cable". That's a 50 Ohm cable (RG58/CU or the like) with a 50 Ohm BNC connector at each end. It doesn't say to *terminate* the cable in 50 Ohm.
The low-frequency attenuator/amplitude calibration is done without such termination, on the cable nor in the 'scope, for the reasons that you found out yourself.
If I understood you correctly, the above should explain away the MEGA GOTCHA.


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