Tube Testing Results

[jensenmann]

I´d stay away from used power tubes. The state they are in cannot be expressed by only two measurement results. Power tubes suffer from mechanical wear of the filament, which loses partially it´s surface material. Just to name one example. Going into detail would fill pages and requires someone with better english skills than mine.
Though I did a lot of tests with old and new tubes and I´m absolutely into NOS I never bought used power tubes for any of my amps. It just makes no sense.

[fireberd]

I used to work as an amp tech (in Nashville). The only true way to "test" a tube is in the circuit. A tube tester can lead you astray as it doesn't really test under actual voltages and use.

[badstrat]

Thanks guys,
I probable jumped the gun buying these as reputable NOS dealers charge about $400 to $600 for a matched pair of these tubes in used but good condition.Paid $150 a pair for mine.I'll get myself a pair of current production tubes and get my amp tech to test and compare and give me the verdict on the Tung -Sols.He knows his stuff as he designed and built the amp and I've been giging the amp for over thirty years. Its called Baez, a 100 watt head, made here in Newcastle, Australia.He's just built a prototype for some new amps he's gonna build.Any advice on a good 6550 tube.

[jaddie]

The typical tube tester is pretty reliable in telling you a tube is completely shot, but there are varying degrees of good. A really good tester can tell you when a tube is questionable, but +1 to the in-circuit method. Some circuits are very tolerant, some are not. Some may even "like" a "soft" tube set a bit better, for many it's a matter of taste.

[emrr]

Yes, most tube testers are simply the first gatekeeper, telling you whether or not a tube is worth looking at further.

The problem with NOS comes in with 45's, 6B4's, 10's, 50's, etc. You pretty much have to buy used.

[badstrat]

I decided to go with some Sovtek 6550WE if the Tung-Sols don't work out and I'm rolling some used 12ax7 pre amp tubes, and the 1958 RCA long black plates really did get an inprovement in sound and was a lot smoother and harmonicaly rich compared to the Sovteks that were in before.The only problem I had at a gig last night was trying to clean up the sound without loosing tone and sustain but I think it's more to do with the amps sweet spot. It seems to sound much better driven a bit harder on the master volume and this can tend to be a bit loud in a lively room. Winding the preamp back doesn,t achive the same result. I'm gonna try a couple of 1960's Sylvania long grey plates for tonights gig.They tested much higher;

(Tested on a Hickok 533A where 1250/1250 is "new", these read 1800/1750 and 1650/1600.)

Thats what the seller said anyway.Cost me about $12 each.Got 8 of them.
Cheers

[badstrat]

Had great success with the tube changes last night.I changed the V1 to another RCA Long black plate and changed the second stage tube to a Sylvania Long Grey Plate. Didn't experience any of the problems of the night before and had an increase in gain and bottom end having to turn the bass control down to 1/4 from 1/2.It seems the combination of the two different tubes created a great tone that cleaned up well with softer picking or reduction in guitars volume knob.I am 100% satisfied with the results and will get my new power tubes and bias done as I noticed the dates on the old ones is 07, so it could be 4 or 5 years since they were changed.Just to let you know the other factors, I use a '79 Strat with a clean boost built into the guitar, no peddals except for a delay, Baez 100 wtt into a Marshal 1960a with celestion G12T-75. Might like to try some Greenbacks some day but I'm happy with the t75's.

[Bill Way]

Check this link for an interesting piece on tube testing by Kevin Deal at Upscale Audio.

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