Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => AmpTools/Tech Tips => Topic started by: patricks on March 24, 2024, 07:31:33 am
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Hi everyone!
I’m looking for advice on testing procedures for valves other than triodes, using as simple testing equipment or procedures as possible, please.
I recently bought a 1964 valve television (chassis, valves, passive components, hardware, and transformers and chokes) intending to use it for a valve theremin. It’s come with plenty of valves, but many of them are non-triodes. I’m hoping to use as many as possible for the theremin.
There list of valves includes:
6ES8 (ECC189) twin triode
6HG8 (ECF86) triode-pentode frequency converter
6BY7 (EF85) RF pentode
6AM8A diode-pentode
6EA8 (equivalent 6GH8) triode-pentode
6DX8 (ECL84) triode-pentode
6BL8 (ECF80) triode-pentode
6GV8 (ECL85) triode-pentode
6CM5 power pentode
6AL3 (EY88) half wave rectifier
1S2 half wave rectifier
Any tips on basic testing?
Heater continuity I can do easily, and I’ve read posts elsewhere about setting up a basic circuit and measuring B+ to see whether it’s abnormally high or low.
I’d like to avoid hunting for a valve tester, with the age of most I expect there’d be at least as much effort in getting the tester working and calibrated as there would be in testing the valves
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... I’m looking for advice on testing procedures for valves other than triodes ...
I’d like to avoid hunting for a valve tester ...
It seems like you need, "An easy way to test multiple types of valves, with quick reconfiguration between valve-type, and an easy-to-interpret indication of whether the valve is serviceable."
That's literally a description of a valve tester. So it seems wise to look into buying a service-grade valve tester. Those things were purpose-made for the TV repairman to take to the customer's home to test their TV valves.
... I expect there’d be at least as much effort in getting the tester working and calibrated as there would be in testing the valves
You don't need "calibrated" but rather, "Which ones are dead, which ones are still kicking." This grade of tester was a few-hundred-quid 2 decades ago, and is still a few-hundred-quid today (are the enthusiasts dwindling faster than the testers?).
Or skip testing altogether and try the valve once the theremin is built. If it doesn't work, buy a new, tested valve from a vendor.
There's not really an easy way to cheaply make a tester capable of testing a wide variety of valves that undercuts simply buying a working 1950s or 1960s valve tester. Pursuing that "inexpensive home-brew valve tester" will likely spend the money you thought was saved in buying the 1960s TV rather than purchasing just the parts required to construct a theremin (such is the challenge of salvage).
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Thanks very much, that’s good advice.
Using the “suck it and see” method once the theremin’s built will be the way to go. You’re right, I saved a lot on the chassis, transformers, and hardware, and a valve tester in working condition will eat all that up :)