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Old 13th June 2011, 10:40 PM   #11
tomchr is offline tomchr  United States
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From what I understand, as long as the dials spin, the box is usually OK.

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Old 13th June 2011, 11:30 PM   #12
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Quote:
Originally Posted by dchisholm View Post
That's the behavior I also recall from the early 1980's. Yes, it IS very disturbing to see that needle peg against the high stop.

Dale
Mine did that too. It sat on the shelf for over a year after i first got it as i thought it was broken!
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Old 14th June 2011, 02:14 AM   #13
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Thanks audiohead, kevinkr and dchisholm for your response.

Yes, the instrument powering up is just like that and you need to wait for about 1 second to let it settle down to a working state.

Thank you all.

WK
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Old 29th July 2011, 12:27 AM   #14
davada is offline davada  Canada
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This is normal for 339A.

Looking at the meter amp I see why.

Until the Q1 Jfet is biased off the meter is at full deflection.

David.
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Old 29th August 2011, 12:12 AM   #15
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That tracks.... Making Diode CR3 an anti-smoke clamp limiting voltage to one junction drop max across the movement. But being old Hp, these are jeweled Darsonval meter movements, not taught band types, so they'll take pegging more gracefully.
Doc
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Old 10th October 2011, 12:30 AM   #16
richiem is offline richiem  United States
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The mechanical design of the 339 and similar era gear was not HP's finest moment. The knobs are terrible -- weak, prone to break or crack, the dial skirts pop off the knob, and the printing is hopelessly fragile. I've used a very fine-point Sharpie to ink in the markings but it's a lousy fix.

On the good side, the 339 is a pretty good analyzer if you can live with about 0.001% as best resolution. The null floor is decent at about -110 to -115dB, so higher resolution is possible. The quad op-amp in the filter circuits needs to be replaced with a quieter unit, especially if you use the analyzer output to drive a wave or spectrum analyzer.

The oscillator is quite good -- better than the analyzer, which it should be for trustworthy use. The 239 oscillator is almost identical but is better in terms of noise, especially since you can isolate chassis ground (or not) with a front-panel switch. Nulling of the oscillator's 2nd H can be improved by padding one or the other of the 2k input/feedback gate resistors for the AGC JFET -- improvement can range up to 10dB. Doesn't affect 3rd H or higher.

My two cents...
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Old 4th February 2013, 12:17 AM   #17
6L6 is online now 6L6  United States
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I realize this is a bit of a thread necro, but there isn't a good reason to start a new thread...

Can the 339A measure IM distortion by itself?

THD seems nice, but talking to some people and reading about distortions for audio, it seems that IMD is much more important than THD...

The 339a seems to be a nifty tool, I am considering getting one for the bench, as without one, or something similar, you are blind to seeing distortion. I'm not a tech, just a hobbyist, but it's cheap enough that it looks like it could be useful.

Any ideas or comments? Thanks
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Old 4th February 2013, 12:28 AM   #18
davada is offline davada  Canada
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Originally Posted by 6L6 View Post
I realize this is a bit of a thread necro, but there isn't a good reason to start a new thread...

Can the 339A measure IM distortion by itself?

THD seems nice, but talking to some people and reading about distortions for audio, it seems that IMD is much more important than THD...

The 339a seems to be a nifty tool, I am considering getting one for the bench, as without one, or something similar, you are blind to seeing distortion. I'm not a tech, just a hobbyist, but it's cheap enough that it looks like it could be useful.

Any ideas or comments? Thanks
NO. Only one oscillator and the required filters are no supplied.

Nothing special is required for IMD in the way of ultra low disto oscillators.
Have a look at the QA400 from QuantAsylum. It can do IMD and with an external notch filter and low disto oscillator it can measure below harmonics -120dB.

The 339A analyzer is a boat anchor.

Cheers,
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Old 4th February 2013, 12:44 AM   #19
kevinkr is offline kevinkr  United States
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The 339A is a boat anchor only in the sense that it is a bulky bench top unit, its performance is still quite respectable.. It will do thd+n measurements and has a 400Hz HPF, 30kHz and 80kHz LPFs as standard..

I used one all through the 1990s and were it not for the computer based FFT setup I generally use and a refurbished Amber 3501A I would definitely have one.

It will measure distortions levels reliably below 0.01% and has one of the cleanest and best performing sine wave oscillators I have ever seen. Residuals on the unit I used were around 0.002% or better which for the era was pretty good.

No IMD option however.

I would recommend a windows computer with Audiotester V3 and Pete Milletts Soundcard interface..

See my attachment for what is possible with a sound card. This is a capture of an acquisition loopback at 500mV and 10kHz.. Sample rate is 96kHz, and I can measure to a little over 40kHz, I can go faster if I need to do broader bandwidth measurements, but at some penalty in sfdr..

I have the luxury of dedicating an entire machine to this purpose although I will probably leverage it a bit for use with the uTracer tube tracing hardware I just bought.

This set up can also do multi-tone and any pair of frequencies within the allowable range based on sample rate. Below 10kHz and 2kHz at 1:1 just as an example. You can see sum and difference tones at 8kHz and 12kHz which will give you a sense of the IMD performance of the measurement setup.. Considering what it all cost it's quite decent. I'm still working on it..
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File Type: png screen capture 500mV.PNG (126.1 KB, 311 views)
File Type: png mutli-tone.png (182.0 KB, 295 views)
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Old 4th February 2013, 05:27 AM   #20
richiem is offline richiem  United States
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Just a comment about IMD and THD. The causes of both forms of distortion are the same -- the non-linearities of amplifiers and passive components. In essence they measure the same things by different means. Neither form of measurement is preferable to the other, and both are limited in accuracy by noise and the performance of the analyzers used.

The HP 339 is not state-of-the-art, and hasn't been for a good while, but it is useful, especially for testing tube gear and much solid-state gear as well. The oscillator section is extremely good at frequencies below 10kHz. but if you intend to buy one, be prepared for some serious cleaning, repairing, and refurbishing -- most of the ones on the used market are not in good condition.
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