HP 331A Distortion analyzer repair and calibration Mini Documentary

[@davec4474]

Very nice demonstration. I did a wholesale replacement of all the electrolytics on the power supply board on mine when I first got it. I love the build quality of old HP equipment. If I ever get to trying to calibrate it, I definitely will be referring to this video.

[@Paperweight01]

+Dave C I too plan to swap out all the 50 year old electrolytic caps in my 331A. Doing that for a HP 400E and parts that I can get to in a 4342A Q meter. Shooting for the lowest ESR. Lots of tantalums in these things. Sometimes a long lead 100 volt polyester film cap will fit and drop the ESR quite a bit.

[@heavymod9476]

Thanks, love watching these types of videos, and yours is very thorough!

[@pibbles-a-plenty1105]

No, the volt meter is not a RMS meter. It is an average responding meter with the scale indicating the equivalent RMS voltage, which is accurate for low distortion sine waves.

[@danielh4995]

Could you possibly provide more info on the 10DB graduations and how you accomplished it with resistors? I have a 333A that I need to go through and I would like to re-calibrate it as well. Thanks

[@johncunningham5435]

What is the meter accuracy near full scale? working with the mechanical movement your results will vary when analyzing distortion. "Never the less a great restoration for the price, well done"

[@kurchak]

I would love to check the calibration of my new 333A, but when looking at the list of required equipment... I don't even know what a couple of those things are. What I do have is: Function generator (FY6900) DSO (Siglent SDS 1204XE) And of course a bunch of multi-meters and tons of components (resistors, caps, etc). Do you think there are any useful calibrations or at least checks I could do with this equipment alone? Thank you! Excellent video btw.

[@retrotechandelectronics]

The equpment today is far more advanced compared to what they had back then. I used what you have.

[@kurchak]

@@retrotechandelectronics excellent! Good to hear. Maybe I will give it a try then.

[@compwiz101]

I have a 334A that seems to work fine, but the electrical zero is off. Mechanical zero is set with the power off (as indicated in the manual), but with a shorting bar on the input it still shows a small input all the way up to the 300V input setting... still thinking about what might be the best bet to fix it

[@retrotechandelectronics]

did you work through the complete cal procedure?

[@wa4aos]

Very well done video.. Thanks Do you happen to know the differences between the HP 331 and 334 distortion analyzers? Thanks again. Glenn

[@retrotechandelectronics]

I think the 334 has an auto dip circuit to fine tune in the last portion and stop jitter as an upgrade. I do it by hand

[@georgegonzalez2476]

Often the wafer switches are very intermittent and need a lot of cleaning. Also often the many electrolytic capacitors not in the power supply are high dissipation factor and low capacitance.

[@retrotechandelectronics]

Any switch that old will be ready for a cleaning.

[@Pootycat8359]

Wanna get RICH? Design a type of electrolytic capacitor, that will last as long as a resistor!

[@retrotechandelectronics]

It wouldnt be electrolytic, but a 15lb polypropylene