The 3455A was a dinosaur when it was first released.
The 3455A and 3456A were sold side by side, with the
3455A being about twice as expensive as the much more
capable 3456A. The 3455A's interesting feature was
it was supposed to be cheap to calibrate. All you
had to do to do a complete calibration was to unplug
the module in the back panel, and replace it with a
recently calibrated module. The idea was you could
order up a calibration by mail, and return your old
calibration module as a core... never having to send
the full meter in for calibration.
Interesting idea, but surely not worth twice the price
of a 3456A.
I say it was a dinosaur, because it used all small
scale logic rather than large highly capable hybrid
circuitry, like the 3456A. It should be much easier
to repair, but it should also be much less reliable.
And, that is my experience with the two units.
-Chuck Harris
paul swedberg wrote:
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With respect to the 3455 and 3456 the difference is night and day. I have
numbers of 3456s and was given a seriously troubled 3455. Quite a
interesting meter.
Replaced at least 11 actually malfunctioning chips on the logic board. The
logics simple so easy to verify the chips were bad. No shot gunning
involved. Never really did get it working but ended up with a different
3455 that needed help and the AC board and it is in fine shape. With
respect to the old 3455 it has both a logic and voltmeter issue. The 3455
uses an unusual processor and teh DVM uses the same proc and a masked eprom
that is known to go bad. It acts as a state machine.
The 3456s are losing there eproms and copies can be found on the net. Thank
heavens.
Regards
Paul
WB8TSL
