DIY Valve Tester Build, Re-Build - Part 1.

I built this basic valve tester about 14 years ago, it was a basic emission tester. I'm going to re-build it with a bit more functionality. The ability to test gm, as well as a beefed up current capability and a better high voltage anode supply using a valve regulated power supply.

[@BrumAdam]

Interesting stuff Andy! Looking forward to part 2 (which I am going to watch next).

[@f.k.burnham8491]

Andy- a few decades back I saw a plan in either QST, CQ, or one of the Ham mags for building a load tester for transformers using 4 6BG6 HO tubes. That is one rugged tube. IIRC, that circuit could be used for what you want to do with a little modification. Likely mid 50's to mid 60's vintage mag. I have found a few PS that use the 6BG6 tubes for adj. voltage. A bit more bulky than the solid state stuff, but very forgiving. You can usually overload the heck out of them for a few seconds to red/orange plate conditions and not harm them. I'd add a fan for cooling them. They are the basis for the tester I am designing to test the cases of tubes that the testers can't test, as they are transmitting or industrial tubes.. If you have gas problems, take and put the tube into an inductive heater, and it can often re-flash the getter, there by absorbing the gas/oxygen that has leaked in. Also if tubes have been sitting idle for a long time, just run the filament for 5-10 minutes and that helps. On mercury vapor rectifiers, like 872's, the mfg. suggests 30 min filament warmup to vaporize the mercury, otherwise you can get arc over. ( I worked on industrial machines that used mercury vapor rectifiers, and it was a total cash cow because the employees wouldn't wait the time needed, and kept blowing out the rectifiers from arc over. The machines used 4 or 6 (3 ph. on the big machines). $$$$$$.

[@diabolicalartificer]

As you say Frank valves are more forgiving than three legged fuses; they don't like it up em : ) Sorry, UK 70's TV series called Dad's army joke. I have tried various things to revive valves but with little success so far. TFW.

[@ianmorgan6104]

Looking forward to this VT build, often wondered how one is built / works : )

[@sa8die]

great video,. and information thanks

[@diabolicalartificer]

Thanks, and TFW.

[@Biokemist-o3k]

New subscriber here. I cannot find the data sheet for my BBC TQ 2/3 Thyratron. I was hoping I could switch 2,000 volts at 60 to 120 times a second. Would you know how I would wire the Thyratron to do this? Thank you in advance my friend. You do some awesome stuff. I am sharing your videos with my friends. I hope you can help. Thanks again

[@diabolicalartificer]

Hello, thanks for your interest. First off have you tried to ID your valve by visual comparison on the National Valve Museum website? Valves often have a few ID numbers. Second are you trying to build a thyratron power supply or for some other purpose like Tesla coil control? Check this paper - ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/1g05fd90k?locale=en it's full title is Electronic Pulse Generator For Thyratron control. Lastly I'm no expert on this subject but from the little I know thyratrons have different bias conditions depending on the gas or chemical properties. If I have a valve with no datasheet I'd start by ID ing what pin goes to what electrode. Then apply voltage to the heater/filament with a bench power supply whilst monitoring current, with a thyratron leave for 30 mins. Next apply about minus 100v between control grid & cathode/filament, then connect a high voltage supply to anode whilst monitoring current. Take it slow. Next make the grid more positive, slowly, all the while monitoring current etc, hand on HV PSU off SW.. At some point the thyratron will trigger, it'll slam on, note the voltage it triggers. Next apply an AC voltage to the grid. It'll take hours of work and needs some hefty power supplies. You could though just buy some thyratrons that have datsheets. I have boxes of them if you want them free of charge & are in the UK/Europe. Good luck, but be safe, the voltages these devices work on can kill.

[@Biokemist-o3k]

@@diabolicalartificer Awesome! When you find out what I am building I am sure you will absolutely be on board. How do I contact you?

[@Biokemist-o3k]

@@diabolicalartificer Thank you!

[@smalcolmbrown]

Keep the IRF830 MOSFET and add current limiting to crash the gate voltage when they go over current.

[@diabolicalartificer]

The MPSA42 is supposed to do that, together with the 22r resistor, but in practice I've found the mosfet always dies under transient conditions. You can get linear fets, but they ain't cheap, hence the valve regulated supply. Thanks for your IP & TFW.

[@smalcolmbrown]

@@diabolicalartificer do you have a circuit diagram that I could see?

[@diabolicalartificer]

@@smalcolmbrown It's there @ 21:03 I'd appreciate any thoughts or improvements you have.

[@smalcolmbrown]

@@diabolicalartificer Assuming that the arrow is the out to the anode and screen the protection is not going to protect anything. 22 ohms means a limiting current of 30mA. I would love to send you a screen grab of the circuit I have infront of me (mostly Steve Benches RAT tester that I planned on heavily modifying.)

[@smalcolmbrown]

@@diabolicalartificer I sent you an email