Tube Testers

[domct203]

Well,

The NOS / Vintage tube bug has it's fangs in deep.

I'm considering a tube tester, but need some education first. I've noticed that different testers use different scales of measurement, and I did not know if there was a perferred scale. Also, I don't need to check every tube ever made, just your basic guitar amp variety (6L6, EL34, EL84, 12AX7 etc.).

Any and all suggestions are welcome,

Dom

 

[212Mavguy]

Tough to beat a Hickok cardmatic for ease of use, but they are way spendy. The tv7 military tester by hickok is also expensive, but it is commonly used by ebay sellers. 500-700 bucks. Tube testers are nice, but sometimes a tube, particularly a power tube, will perform different in circuit than in a tester. For instance I got a pair or Brimar 6l6ga on ebay, they tested like new strong, but there was a problem with the control grid on one of them, and in my modded Fender Champ it did the runaway over current/overheat thang. I had a multimeter hooked up to a test jack I had earlier installed in that amp so I was able to yank the rectifier tube in time. Have not tried the pair in my Siegmund in class AB fixed bias yet, though. I'm sure they will be fine in that application.

The vintage/new old stock disease is a fun obsessive compulsive disorder to have as long as you buy carefully and shrewdly. :wink: demand is increasing, supply is decreasing... 8)

 

[stokes]

Tube testers can be useful to an extent,but the only true test is in the circuit it is intended for.Not long ago I did some work on a Bassman 20 for someone.The power tubes were pretty much dead,original 6V6's from '82.I put them in my Weston gm tester and they tested like new,same results in an emissions tester.I recently got a Triplett 3444,which is closer to a lab grade tester,same results for gm.This tester has a gas test which both tubes failed miserably.So if you want to get a tester forget the emissions type,they are pretty much useless.You want a gm tester,but get one with the gas or grid leak feature as well.The noise test is pretty much useless,I've tested tubes known to be noisy in an amp and the test shows nothing.Another consideration is the plate voltage the tester uses.Most testers only use between 100-150 volts,not enough to show how the tube will perform.The Triplett I have gets up to 250v's,a little better.What I like about this tester is you can vary the test parameters i.e. plate volts,grid bias and signal.I actually use the specs in the RCA tube manual and a good tube will show the gm listed in the specs.Most testers read "proportional gm",not the actual gm of the tube.Another thing to remember is that any tester you get on ebay will most likely need to be calibrated and be in need of some repair.If you have lots of $$$ there is somebody called Amplitrex making a modern unit,the AT1000 that goes for about $2500-a little much for the hobbyist.If you go to alltubetesters.com Roger Kennedy gives some good info on testers.