Seems like you are on the right track.? Many HP scopes of that era lose their minds if the memory battery goes dead.
Peter
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On 2/24/2025 11:09 PM, Radu Bogdan Dicher via groups.io wrote:
Hi all,
Over the weekend I've got a couple of 54512Bs at my desk to seek to bring back to full functionality. My main scope is a 54522A, and I assume they have some commonalities, but I've yet to open mine (it came to me fully refurbished and never needed to open the case). I'm not very familiar with this other series, and hope on some good input and recommendations.
The documentation is not as good as others I've seen from HP. Specifically for this unit (54512B), Keysight only seems to have a very skinny (by HP standards) Service Manual which can't honestly be called "module-level Service Manual," as it doesn't really into much detail on the different modules. Then there's a "Front Panel Reference," which is an odd other way of naming what I think is the Operating Manual. A couple other manuals have to do with programming. That's it.
Sometimes in a series you have to look for the main unit, but in this case I'm not sure that's the 54501A, as the catalog spec sheet seems to suggest, or the 54505B, as per the SM. Maybe someone very familiar with the series would know. Artek doesn't have manuals for the 54512B at all, but they do for the 54501A, and if applicable, I'd get the series of six manuals they sell as a bundle. If no go, I'll be a bit in a bind with fixing this given what I have at hand. I am aware HP was not longer offering component SMs by this point, though I don't know for a fact on this specific series and scope (but I do regarding the better?/later? 54522A).
Is this really capable of FFT to 500MHz, even if the scope is rated to 300MHz? I can't make sense of that.
Now, on to the specific issues with the units.
*Unit #1 *(S/N: 3214A00705)
* Upon starting it, it reports something like "TRYING TO START REALTIME
CLOCK," which is unsuccessful after a time countdown from I think 60:
"REALTIME CLOCK FAILED TO START - DISABLED."
* Once I get it to display the default screen and output a trace, it stated
"Default cal loaded. Re-cal instrument."
* Self Test passes all.
* I'm also seeing a solid and apparently accurate 5V from the DC Cal output
in the back. I haven't tried the AC Cal output.
* Note this one had the Cal switch in the back in the UNPROTECTED position
when I got it.
* I'm able to display the square wave test signal from the front panel.
*Unit #2 *(S/N: 3214A00704: consecutive units!)
* Upon staring it, it stated "CALIBRATION FACTOR CHECKSUM ERROR. MOVE REAR
PANEL CAL SWITCH TO UNPROTECTED. POWER INSTRUMENT OFF AND THEN ON AGAIN.
RE-CAL INSTRUMENT."
* It also says "Trying to start realtime clock (09290)." Maybe that's an
error code?
* Upon switching the rear Cal switch to UNPROTECTED, it boots successfully,
goes to a default measurement screen, but gives me a warning "Failed
interpolar cal." The trace seems to jump around on Y a bit.
* Self Test passes all /but/ Timebase. It also displays the same error as
default screen ("Failed interpolar cal").
* 5V out at DC Cal is good.
* This one had the Cal switch in UNPROTECTED position, so maybe that's why
it booted successfully.
* I'm able to display the square wave test signal from the front panel,
though it seems to be offset vertically a bit.
To me, this seems to tell me the battery holding the cal constants is done - going by what I know about my 54522A. It's also possible some Dallas RAMs are out of battery - though I don't know if this uses those for non-volatile memory. I have not yet opened the units, so I've no idea where the rails are, if any caps have leaked, etc. But maybe the information above gives some clues on what's going on, enough to start thinking on it. It also seems the issues are shared very similarly, so maybe that's making the repair more streamlined.
Looking forward to your input.
Thank you,
Radu.
