In article ,
says...
"John Miles" wrote in message
...
Thanks.

I'll look at those pdf files on ebay.

The uncal light is unfortunately always on, none of the settings affects it.
The controls seem to work, but they don't affect uncal led. I guess I really
need the manual. Probably something in there that could explain it.

That would make me suspect the keyboard controller chip. In the 492, I
ended up replacing it with a BASIC stamp (which I still have in the junk
box somewhere; you're welcome to it if that's the problem).

Does your TIME/DIV knob do anything at all?

-- jm

What puzzles me in that case is why are all of the functions/buttons working?
Yes, even the TIME/DIV works as expected, all positions. Same goes for other
buttons.

When I turn it on it always starts with some strange settings and I need to reset it,
perhaps the EEPROM or RAM has failed over the years. Or I don't know how to
store the settings.

That's odd, all right. With my 492, I had to manually rotate TIME/DIV
back and forth into the AUTO position after power-up to get the
instrument to read it.

I'm not sure what would cause random or non-standard power-up settings
besides a flaky keyboard controller that doesn't respond to the CPU's
first few accesses after power up. The 496 doesn't have the capability
to store its settings in NVRAM like the 494 and later models, so it
shouldn't be a case of corrupted memory. The EPROMs are checksummed, so
if you don't receive any power-up error messages, they are OK.

I suppose one worthwhile test would be to make *sure* that the UNCAL
light is on for no good reason (as opposed to invalid startup settings).
Power it on, rotate TIME/DIV back and forth leaving it in 5
seconds/division (the slowest setting), and manually set the other
controls for 1 MHz RBW and 100 MHz/division sweep with no video
filtering. The UNCAL light should definitely not be on at that point.
If it is, you can disregard it for the time being if everything else
works right.

I'll poke around in my 492 manual and see if anything leaps out at me.

-- jm

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