Tube Tester

Devon8822 · Post by **Devon8822** » Sun Apr 15, 2007 12:24 pm

I need something to test tubes, to see if they are still good and useable or if they are dead. Are there tube testers? I just need t be able to test el34s and 12ax7/ecc83 tubes. Are there little amps that use 1 of each of these tubes? I know the Valve jr is good for testing ecc83s, can i mod a jr to take el34s instead of el84s though? Anyways, what options do I have for this? Thanks

Post by **VelvetGeorge** » Mon Apr 16, 2007 5:12 pm

You could rewire one for an EL34. but I'm not sure if the PT can deliver the heater current needed.

The best octal tube tester IMO is the maximatcher.

maximatcher.com

VG

paulster · Post by **paulster** » Mon Apr 16, 2007 7:19 pm

Running the VJ with an EL34 has been tried over at 18watt.com. It appears that the PT can supply just about 2A of heater current so an EL34 and 12AX7 work fine, and it's a simple mod to add the octal socket as an addition to the noval.

I use mine when I want to evaluate 12AX7s as it's running high gain on both triodes so shows up microphonics and poor sounding or noisy tubes really easily. You can't get a much simpler circuit so you really get to hear the tube itself.

For matching power tubes I'd still follow George's advice and look at something like the maximatcher though.

Devon8822 · Post by **Devon8822** » Tue Apr 17, 2007 10:54 am

That thing soudns liek a good idea I will check it out, hopefulyl its not killer expensive. Are they're any alernatives to that one? just so I know all my options? thanks

acdc51502112 · Post by **acdc51502112** » Tue Apr 17, 2007 6:02 pm

would it also be possible to use a Epi valve jr as a tester? As in, taking out the power in the epi and putting in one of my power's, and also doing this with the pre's. thanks

Devon8822 · Post by **Devon8822** » Wed Apr 18, 2007 8:29 am

yeah, thats the whole idea for the thread, there are just alternatives to that if you get a another tester than you match your power tubes and test them on the same thing.

Devon8822 · Post by **Devon8822** » Thu Apr 19, 2007 11:05 am

What are some alternatives to the maximatcher, so I can compare? Im no amp tech so it might be a bit much aswell. I will probably have to go with a modded valve jr, and take tubes to a tech if i need to match any.

tubetramp · Post by **tubetramp** » Fri May 04, 2007 3:13 am

look in gerald webers desk top editon for the homebrew matcher. you can concoct this with little effort some wire a one ohm resistor and a 5 dollar harbor freight meter.if youve only got a few sets to match this is a cheap way out.if your matching stuff on a commercial level the maxi is hard to beat regarding accuate measure of plate current and true mc . ive seen some homebrew skew gadgets that give you real time measurement and data on every pin.never made a shits difference at the end of the day.but it is nice to know your not to far off.tt

N3m0 7h3 Fi5h · Post by **N3m0 7h3 Fi5h** » Wed Dec 05, 2012 10:29 pm

I know, it is an old thread ..

Devon8822 wrote:I need something to test tubes, to see if they are still good and useable or if they are dead. Are there tube testers? I just need t be able to test el34s and 12ax7/ecc83 tubes.

I come over to this page: The Rikstone Simple Tube Tester
http://www.kolumbus.fi/risto.kivioja/Ri ... Tester.htm" onclick="window.open(this.href);return false;

RikstoneAmps wrote:Tube tester for EL34, EL84 and 12AX7 (ECC83)

This is a simple tube tester which is based on a schematic published
in the middle 50's in a Polish radio amateur magazine.

You cannot reach 100% test coverage with this tester. Actually there are only
two different test cases you can perform. One of them is the check of anode
current when changing grid voltage. When grid voltage is set to same potential
with the cathode by using the "control switch" the anode current should remarkably
increase. Another test you can do is the check of the heater current. Note that in
both tests a separate current measurement instrument is needed.

The schematic is generic which means you can quite easy add many type of tubes to it.
Before you add any other tubes make sure that all the pins such as anode cathode
grids and heaters will be correctly connected. A good reference for that is the current
schematic and data sheets of the tubes.

The main component of the tester is power transformer that shall fulfill the requirements
of the tubes you are going to test. E.g. in case of the EL34 tube the heater current can
shortly exceed 2A. In order to protect the transformer three fuses have been added
to the schematic.

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