modern oscilloscopes

scopes

or so

DAC.

Maybe for offsets and tweaking varicaps, but not in the signal path.

The cal stuff is there too, but you can recal the head after installing a new eprom; the mainframe has a screen for that. I suspect that blowby compensation, and maybe some TDR controls, may be in there too, but I don't know how to recalibrate those.

If JWs file works, I'm off the hook. If not, let me know and I'll find the head that we reflashed, and extract the code.

You are off the hook. It turns out I have a programmer (BP Micro) that will do that chip. And the code from JW works. The bad news is that I seem to have a blown internal 50 ohm resistor. TDR shows the input impedance at 2.3 k. The measurements on that channel are all 2x real. Oh, also it is a SD-26 head, not the 24. I'll do some digging and report back the findings.

Thanks all, tm

Did the SD24 cal table work in the SD26?

If the terminator is blown, and it still samples, I'm impressed. I would have guessed that the sampling diodes would be trashed, too.

Actually, these heads are pretty rugged.

Yes, the copy from the SD-24 works well in the 26.

If I overlay the a & b channel with the calibrate signal fed through a power splitter to both channels, It looks like a single trace. The vertical gain is 50 mv/div on the bad channel and 100 mv/div on the good one.

I am always impressed with this scope. Especially the TDR function.

Anyway, thanks for your comments.

Regards, tm

Then how do they make those fancy displays work?

Beats me. I'm an engineer, not an antiquarian.

I suppose on and off counts as a 1-bit DAC, but that's pushing it. Don't need anything for the raster, that's timed like any other CRT.

The 460 does actually have levels of gray (well, green), but they aren't used much.

Of course, being able to control intensity from within a menu pretty much guarantees a DAC somewhere. And with calibration, probably many. None of them actually running at the sample rate, of course.

Tim

I have seen similar messages on airport flight status monitors.

Always adds to the anxiety I feel over flying.

scopes

or so

DAC.

True. Tek refers to them as daculators.

And what do you think drives an outboard analog display?

?-)

Hamsters.

Cheers

Phil Hobbs

Dear Sir Phil,

I respectfully resent that statement. Every one knows that Hamsters are quite lazy, are Gerbils have far superior work ethics. We're cuter too.

Thank you.

Best regards,

Nibbles S. Woodchipper III.