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"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Thanks guys
Do you know anyone with an HT-20?
If they will let you! Rig a test meter across one of the 7W cathode resistors and monitor the current as the valves warm up (don't forget you need speaker/load plugged in AND a plug in the input!)
If the voltage goes above about 12, the valves are probably shot but you are very unlikely to damage the amp.
Note, the HT-20 runs at a fairly low HT (~300v IIRC) so this will not be a S or Bust test.
Dave.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Valves are already in the bin, not taking a chance with them
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
"And hence (with respect!) a bit pointless! That's the exact problem with using a proper valve tester to assess valves for a guitar amp too - they just don't apply the same high voltages as the valve will see in use, and a valve can easily pass as good on the tester and then fail in the amp."
Yes, well "for indication only then"!
When we had a problem with some EL34s a few years ago, my "tester" was an Artisan 100 run at 253 mains in and heavy music running through it at full chat. The load was a pretty evil reactive jobbie and I used to fit each valve, set bias then give it a bit of grief with a small, rubber clad screwdriver handle. Some 10% of about 100 flashed mightily and died blowing HT and sometimes mains fuses. About 25 % flashed once and took out just HT fuse.
Then the amp went back on the artist loan roundabout!
Dave.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein