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[WTD] valve testing

P

philiphifi

pfm Member
hi everyone

i got a handful of different old tubes: 6922, 5876, 2a3, 300b. Does anyone have a tube tester for noise near Surrey who could help me to see if they are still good and not noisy?

Thank you

Philip
 
So far as I am aware, the only test for noise is to try them in whatever you intend using them in.

Testers test to spec's and they do not include noise, as such.
 
yes, some testers have had headphone jack ,
I suspect you're interested in microphonic noise this could be seen on oscilloscope but you'd need to build simple circuit . I've seen somewhere a circuit ,I think it was on one of German forums which allowed to measure the voltage created but it used fair bit of ss devices.
As pointed earlier tubes are very circuit dependant and same tube in one amplifier could be quiet but noisy in another depending on topology used.
I'd concentrate on basic tests like emission best if tested at different working points, Gm and life expectancy.
I have a tube curve tracer/tester with a computer interface but recently moved homes and still going through things so it wouldn't be quick , another thing I built one for tubes I normally use: 9-pin signal tubes and KT family power tubes and have no time to convert to use for 2A3 or 300B
 
I can't test for noise (except by putting them in a circuit) but I can test within limits for the usual characteristics of 'goodness' - transconductance, emmissions, gas. I use an AVO Mk4 which I have calibrated. For 300b and 2a3 these limits are an anode voltage of 400V, and questionable higher emmission readings which I put down to the 'dynamic' measurement technique employed in the machine and an abberation affecting low Rp triodes. I do cross-reference to the many 300b and several 2a3 which I have tested over the years however. If interested and you can get the valves to Earls Court, London then I'll do this, but you'll have to leave them for a few days because it can take a while.

The 5876 is an unusual transmission valve and I can't test that - but presumably you mean the 5687?
 
jazid said:
I can't test for noise (except by putting them in a circuit) but I can test within limits for the usual characteristics of 'goodness' - transconductance, emmissions, gas. I use an AVO Mk4 which I have calibrated. For 300b and 2a3 these limits are an anode voltage of 400V, and questionable higher emmission readings which I put down to the 'dynamic' measurement technique employed in the machine and an abberation affecting low Rp triodes. I do cross-reference to the many 300b and several 2a3 which I have tested over the years however. If interested and you can get the valves to Earls Court, London then I'll do this, but you'll have to leave them for a few days because it can take a while.

The 5876 is an unusual transmission valve and I can't test that - but presumably you mean the 5687?
Click to expand...
yes 5687. Thank you for pointing it out. Thank you for your offer. I do come to Earls Court but I wouldn't dream to bother you if it takes so much work. Naively, I thought it would just be "stick it in and take a reading job".
 
The small signal valves are each a five minute job. The big triodes could be as well, but shouldn't be if they're any good, the results will be of limited validity .
Power triodes really do need a dedicated tester rather than a technicians pass/fail workhorse. In another life I'd make myself one and test these suckers under real world conditions. Maybe I will, who knows?
 
I can test for noise, GM, gain on the small signal valves using a maxipreamp ii tester (it has an audio out that lets you listen to the valves and underlying noise / microphonic effects), but you'd have to post them as I'm in the midlands.
 
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