Merlin's Mini Tube Tester

[dorrisant]

I know some of you have already seen this...

http://www.valvewizard.co.uk/valvetester.html

I thought this would be a good place for a possible project build. Maybe just a good source for parts.

I haven't built this yet but I'm most certainly going to.

First, does anyone know where to source a small transformer that would do the trick and still fit in a small box?

I built a preamp power supply a while back using a 120 to 9 volt toroid from Amveco. I'll have to check the spec sheet but I'm thinking about using a 12vac wall wart rectified to dc for the filament. Same 12vac tx-ed up to the needed 100v.

I will build... who else? I know I could use one of these for sure!

Tony

btw... also a good place to point out deficiencies and correct them...

[selloutrr]

Neat post

Not to be a downer, but if...

The 100V max test voltage is limiting. Debatable as to how the test results will transfer to in amp performance.

It's neat but if it's not giving test results that are useful it's not worth the investment in parts.

[dorrisant]

I feel you, but 100v doesn't have to be the limit. Maybe VVR could be used to dial in what you need. VVR may be overkill... how about an attenuator network like in the Vox AC4TV...?
If there are more eyes looking for cheap parts, maybe we could source a cheap BOM.

Tony

[Merlinb]

The 100V max test voltage is limiting. Debatable as to how the test results will transfer to in amp performance.

Actually, 100V is a standard test voltage for the numbers quoted on most data sheets. If a valve matches those numbers at 100V, there is a very high chance it will conform to everything else on the data sheet too. A tired valve will also show its failing performance most clearly at low voltages.

Remember, this device is only a valve tester/checker; its not meant for obtaining design information. You would use the data sheet for that (after all, nobody designs a circuit around one particular valve sample!).

[Merlinb]

First, does anyone know where to source a small transformer that would do the trick and still fit in a small box?

If you're in the US/Canada you could use any 6V/2A transformer with a dual primary...

Hammond 266L6 or 266JA12?
http://www.hammondmfg.com/266.htm

182K6
http://www.hammondmfg.com/182.htm

[Structo]

Thanks for the info Merlin.

BTW, I ordered your new second edition preamp book yesterday!

Thanks for all you do for the vacuum tube amp community.