DIY valve testers

[BlueX]

Anyone got experience with DIY valve testers (for guitar amps: 12A*7; EL84; EL34, KT88, KT66, 6V6, etc.)?

I saw these examples (in the thread below):

The uTracer, a miniature Tube Curve Tracer / Tester.

www.dos4ever.com

https://valveheaven.com/wp-content/uploads/2015/03/An-inexpensive-easy-to-build-diy-valve-tester.pdf

If they are any good I think the cost can be justified (not too hard for guitar related stuff, though).

Used testers are rare around here, and those that show up get expensive during bidding.

Looking for a tube tester - advice please

This is a DIY build you can save 80% or more by building it yourself.

www.marshallforum.com

 

[Jon Snell]

You get what you pat for (or make).
I purchased a used ex military AVO 160 for what I thought was a lot of money and now I find it was a bargain as they are now fetching north of £1200!
It is excellent and shows all characteristics that cheaper DIY machines don't.

Basically a medium voltage power supply with a current meter and a method of adjusting the bias voltage will allow you to roughly match valves. Most people are happy with that.

 

[Kuga]

Basically a medium voltage power supply with a current meter and a method of adjusting the bias voltage will allow you to roughly match valves. Most people are happy with that.

Do you could use a valve amp for It? I mean a EL34 push-pull fixed bias amp to test EL34 pairs. Like a JCM900. Adjusting the bias at min settings and taking voltage mesuraments. Do will be enought to can know If you have EL34 matched pairs?

 

[Jon Snell]

You could but if there is a problem with a valve, it may become catastrophic.

 

[BlueX]

they are now fetching north of £1200!

This is my problem. I should've started with this in the '80-ies.

Do you could use a valve amp for It?

Maybe rebuild an old amp, with a PT that can give high enoug HT/B+?
- Rewire sockets to have: Octal, EL84 noval, and 12A*7 noval
- Switchable dropping resistors and connect the "amp" to a variac, to adjust plate voltage
- OT connected to dummy load, to present power valve with suitable impedance
- Potentiometers, and maybe switchable resistors, to adjust grid/screen voltage
- "Start button", Off-(On), to study any response in case of failed tubes
- Measurement socket for each pin
- Fuse all voltage supply

I don't mind using datasheets, and doing manual calculations. I guess I would learn something in the process, as well.

 

[Jon Snell]

For a simple tester you will need a mains transformer that provides the heater voltage and current plus a high voltage secondary to provide about 250volts ish. Tap off the winding to generate a negative voltage for the bias.
Use a potentiometer to adjust the bias voltage and measure the voltage across a cathode load resistor.
Control grid goes to ground/-ve supply.

Something on these lines.
(Smoothing is not required as it is not an amplifier).

 

[StingRay85]

You get what you pat for (or make).
I purchased a used ex military AVO 160 for what I thought was a lot of money and now I find it was a bargain as they are now fetching north of £1200!
It is excellent and shows all characteristics that cheaper DIY machines don't.

Basically a medium voltage power supply with a current meter and a method of adjusting the bias voltage will allow you to roughly match valves. Most people are happy with that.

A fully serviced AVO Mk4 or Funke W19 can be found here for around 1000€. If you're only interested in the typical hifi or guitar tubes, the Maxi Preamp 2 and Maxi Matcher 2 can be had for about 2000€. The nice thing is that they are only a few kg each

 

[Mike_LA]

Last tester thread
Older thread

 

[Jon Snell]

Last tester thread
Older thread

Don't need a green house or new plastic glass for it (check out your link that points at https://losangeles.craigslist.org/sgv/grd/d/montebello-panda-film-55-mil-black/7680833616.html ) .

 

[Mike_LA]

Don't need a green house or new plastic glass for it (check out your link that points at https://losangeles.craigslist.org/sgv/grd/d/montebello-panda-film-55-mil-black/7680833616.html ) .

Yah, sorry about that, old link on my clipboard.
Any interest in something like this?
Shouldn't cost that much to send it to Sweden.

 

[Kuga]

I bought a Cristhmas present for myself. I found a used Maxi Matcher 2. Let's see when It arrives. I will have three days to see If It works properly. I have a lot of power valves. I have one with a faulty heater, some one shorted and a bunch used ones. Specially 5881 and EL34.

 

[BlueX]

A new Maxi Matcher isn't terribly expensive, although the Maxi Preamp is needed to also test 12A*7's. Below I've listed some models I found here and in other threads. With this list I can keep my eyes open if something turns up.

Still tempted to build a kit. The uTracer get good reviews, and price is moderate. Completely DIY, e.g. from an old amp, probably needs to wait until I've got some experience with testing.

New:
- Maxi Preamp 2
- Maxi Matcher 2
- Amplitrex AT1000

Used:
- AVO CT160 (AVO Mk4)
- B&K Dyna-Jet 606 or 707
- Funke W19
- Hickok 600 or 752
- Superior Instruments model TC-55

Kit/DIY:
https://www.dos4ever.com/uTracer3/uTracer3_pag0.html
https://valveheaven.com/wp-content/uploads/2015/03/An-inexpensive-easy-to-build-diy-valve-tester.pdf
http://www.roehrentest.de/RoeTest10.html

Literature:
http://tubebooks.org/Books/Atwood/Tomer 1960 Getting the Most Out of Vacuum Tubes.pdf

 

[Mike_LA]

Here are images of the booklet that it comes with.

 

[Mike_LA]

Ok, I got a little busy reroofing my garage but here a 3 quick demo vids.

 

[neskor]

I have old Neuberger RPM375 and I recently built uTracer 6.
uTracer is more than enough for me.
If you are tight on a budget and have some soldering skills, my advice is get uTracer 6.