HP 339A Teardown

A piece of equipment I use rarely but when I do I find really useful is my HP 339A Distortion Measurement Set. Built in the 70’s this unit has a precision sine wave oscillator and distortion measurement section. One of the things thats really nice is the oscillator and the notch filter are tied together and the notch filter auto-nulls to make measurements really easy to accomplish.

The build quality of this unit is impeccable, made by HP when they were making stuff properly. The entire chassis is made from folded high quality aluminium sheets with capture nuts and really precise machining. The main oscillator switches are coupled using a bar and wafer scheme but both the oscillator and the filter are fully screened and isolated in their own chassis sub-sections. The smell from inside the unit is that old-school electronics smell I used to encounter all the time when I was a kid taking apart old TV’s and Record Players. I don’t know what chemicals exactly make that smell but I am pretty sure if you could bottle it you could sell it – there is an idea for a unique aftershave! It could be called “Ye’old TV Man”!

Anyway, hope you will find the video interesting. Thanks for watching.

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  1. Gerry, thanks for the great video. Based on your review I decided to track down a used 339a to add to my lab. Unfortunately it didn’t come with a power cable and I was told that it uses a non-standard 3-prong connector. Would you happen to have a part number for the power cable, or could you tell me if there is some other commonly available power cable that will work? Thanks.

    1. Hi Robert, thats a great addition to your lab. After watching my own review I have decided to hang on to mine – its just too nice a piece of kit to get rid of. As far as I am aware its a standard IEC power connector, nothing special, at least it is on my unit. If you take a look at the video at 0:0:29 seconds you will see clearly the power connector on the rear of the unit. Use 1080p mode and full screen, its very clear and its definitely a standard IEC connector. Gerry

  2. A nice teardown Gerry. You mentioned that you are going to clean one of the switches. Any advice on cleaning switches and pots in this type of vintage equipment?

    1. Hi Harry, mostly very carefully! I would try not to make physical contact if possible. Use a good brand switch cleaner designed for the job. If you use Isopropyl you will dry out the contacts, the proper cleaner should leave a thin residue of non-conductive lubricant to help the switch contacts stay cleaner for longer. Spray on a little and work the switch for a good while, do that twice or even three times, that should clean them well enough. One of the problems with these kinds of wafer switches is over time the sprung contacts tend to loose some of their spring strength which reduces the pressure which leads to more noise and therefore switch cleaning. Taking them apart is not really a wise thing to do so you are stuck with cleaning them and hoping there is still enough life in the switch leafs to make good contact. Gerry

  3. Hi Gerry, It is very nice video on HP339A, I got much understanding on 339A. I have one 339A, but it have problem on distraction function from one two years already. As it was very old model and cannot find any support in my country ( Hongkong ), would you advise any subjection for repair on it or it is better give up.


    1. Hi James,
      Its very difficult to be specific with advice, I am sure its repairable and probably worth the effort, but I would not know what to advise other than open it and start looking for problems using a scope and multimeter.


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