HP 331A Distortion analyzer repair and calibration Mini Documentary
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- Опубликовано: 10 фев 2025
- This is the repair and calibration of an HP 331A THD distortion analyzer that Id picked up earlier in the month similar to the 334 / 334A without the extra automatic capabilities. Provides for very good total harmonic distortion testing as well as frequency response once finished.
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.
+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.
Thanks, love watching these types of videos, and yours is very thorough!
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.
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.
The equpment today is far more advanced compared to what they had back then. I used what you have.
@@retrotechandelectronics excellent! Good to hear. Maybe I will give it a try then.
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"
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
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
did you work through the complete cal procedure?
Very well done video.. Thanks
Do you happen to know the differences between the HP 331 and 334 distortion analyzers?
Thanks again.
Glenn
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
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.
Any switch that old will be ready for a cleaning.
Wanna get RICH? Design a type of electrolytic capacitor, that will last as long as a resistor!
It wouldnt be electrolytic, but a 15lb polypropylene