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I've noticed excessive through attenuation with my HP attenuator set (8497K / 8494H). The repeatability was out of spec. After switching there would be a difference of 0.1 to 0.2dB. I tried IPA on the RF relay switch contacts with no effect. I was hesitant to try anything more aggressive but with little to loose I applied Deoxit Gold ... and it fixed the problem completely. The spec for through attenuation is 0.4dB + 0.09dB/GHz & 0.6dB + 0.09 dB/GHz. The repeatability is now much better than spec. (I'd already replaced the o-rings)

hi guys my hp8921a power supply has failed and i have installed smps power supplies to power it .these are working ok however i have no reception or spectrum anyalser .the original power supply must put out a signal to the micro that shows it to be working because a error of i think it was power supply fault which the detection line comes from the secvondary ac before the diode.any assistance would be great.

Please Help to identify these parts the +/- supply is biased o whats? ANZAC MD- 824 RF mixer I tested they work well to 1Ghz to 3.8 GHz the LO I put 2Ghz and rf I put 3.8 but I don't get the idea for the supply. Thank you for your wisdom

Re HP 478 A Thermistor mounts could someone –please direct me to a listing of the different options for example HP 478 A - H75 also interested in any one that uses the H75 option Regards Paul

If anyone has a copy of the manual for this old amplifier I'd appreciate a copy. Even just the schematic diagram would be appreciated. I have had this amplifier for years and use it once in a while. There's a DC offset on the output now but appears to have low distortion. Ran on mercury batteries. Now the battery contacts are all corroded so I just connect a power supply to the test sockets. Has germanium transistors and I think it is '60's vintage. 10 Hz to 1 MHz is its frequency range and has 20 dB and 40 dB selectable gains. I did check the files. Thanks! Pete

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.