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Awesome, thank you, Peter.?

I wonder if anyone has a fresh recollection of what battery or maybe battery-backed RAM would be suspect and possibly needed so I'd start working on an order to have the parts ready by the time I carve out some time to open these. From what I know about these generation scopes, replacing the battery is probably a good idea anyway. The cal constants seem to be gone, so nothing to lose there.?

I wasn't able to find this information (particularly info on the battery) in the manuals, which I find odd.?

Radu.?

On Tue, Feb 25, 2025 at 5:26?AM Peter Gottlieb via <hpnpilot=[email protected]> wrote:

Seems like you are on the right track.? Many HP scopes of that era lose their
minds if the memory battery goes dead.

Peter


On 2/24/2025 11:09 PM, Radu Bogdan Dicher via 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.
>