Tube & tester score

[gui_tarzan]

There's this old TV repair shop nearby that's been closed for 5-6 years and I've wanted to check it out since then. Driving by on my way home from work the other day I saw an auction sign in front of the home. Today I stopped by and to make a long story short, the guy there directed me to the owner's house a couple of miles away. After spending about an hour listening to him and his brother and their stories I asked if I could purchase some tubes and a tester, which he just happened to have brought home from the shop yesterday.

Total cost?

$25.00

I was in the right place at the right time.

Yes, the tubes are all NOS, unused.

[passfan]

Excellent score, especially the tester.

[Leo_Gnardo]

Ya-hoooo! Some real 'made in New Jersey' Tung-Sols! I lift my mug of birch beer to salute you.

I worked on a similar tester recently. It used an 83 mercury rectifier - which had given up the ghost, no worky. Didnt' see any 83's for sale so replaced it with a pair of 1N4007 and it's back to functioning. Had no way to calibrate it, but I got good readings with good tubes so close enough for rock and roll.

[gui_tarzan]

Here's a site with free Hickok schematics, manuals and such, one of which is calibration instructions.

http://www.stevenjohnson.com/hickok/data.htm

[Stevem]

That's a great tester I have the 1955 era model of that one and at that price you might as well call it free!
Go thru it, change out all the resistors can caps and tubes now as if it has the number 83 recto in it they are getting hard to find, then get the needed spec 6l6gc tube from SND and then do the calibration on it.
Next your gonna get a 9 pin and oectal socket from AES to use so you do not beat up the sockets in the unit itself!

[Firestorm]

And make yourself a cheat sheet of settings for the tubes you'll test most often so you're not always spinning through the damn scroll!

Hickoks are great testers, the one caveat being that you can't really count on them to match power tubes because of the low voltage they apply.

[gui_tarzan]

I wonder if there's a way to push up the voltages with an external power supply and check for true performance. For example, if a guy were to take a socket normally used for testing bias and re-wired it with appropriate wire and a power supply...

[Leo_Gnardo]

I wonder if there's a way to push up the voltages with an external power supply and check for true performance. For example, if a guy were to take a socket normally used for testing bias and re-wired it with appropriate wire and a power supply...

For testing at higher voltages you might build from scratch, or convert a scrappy old amp. In my workshop there's a funky Heathkit W-4 I restored, and use daily to test output tubes at real-world voltages. This particular model has a quarter inch jack next to each output tube, into which an ammeter is plugged to measure cathode current. I made a wooden panel with a pair of $10 100 mA meters and there's a tester for ya. I've been using it for 15 years almost, and it's been a treat. I ran separate cathode R's for each tube to reduce interaction between them. One of these days I'll put in a bias supply and switch to select general 6V6, EL34, 6L6, and 6550/KT88 levels. Another thing I may do is put in a generic OT and sell off the Heath's to some collector. They're supposed to be a bit fragile but this one's put up with some tubes that shorted and it's survived so far. I added an HT fuse that hopefully has and will continue to protect the OT. The PT went bad even before I put the amp to work, due to a bad filter cap, and I replaced it with a junker PT that fills the bill, with @ 450V on the plates, rectified with a tough old 5V4. To make life a little easier for 6V6's I switch the rectifer to a 5Y3 when testing them.

I wouldn't hazard applying higher voltages within your Hickock.

[gui_tarzan]

No, I wouldn't either. It was just a thought, though it would probably require building one from scratch to test at normal voltages.

[Stevem]

years ago I picked up a forlorn 20 dollar silverface champ that I set up to match output tubes in with a spate PT just for the heater so I can power two outputs at once and I ditched the recto tube for a SS power section.
With my variac on the champ and them pumping in 4 different test tones while reading the drive signal into pin 5 I can get matches as close as 3 percent!

[gui_tarzan]

So what would prevent someone from using some organ parts (transformers) to do the same thing? I'd be very interested in hearing more!

[Leo_Gnardo]

So what would prevent someone from using some organ parts (transformers) to do the same thing? I'd be very interested in hearing more!

If you're going to scratch build, the transformers don't care where they came from. Mostly you want to make sure you have enough filament current to support whatever large tubes you may want to run in it, 2 amps apiece for KT88's for instance plus whatever pre tubes you may want to use. A 6A filament rating would handle just about anything you can throw at it, testing a pair at a time for push pull balance. If you go for a separate filament transformer, they're pretty cheap. Unless you get one from Mercury.

[dorrisant]

Nice tester!! Can't beat that deal with a stick.

[gui_tarzan]

Leo, the last organ I took apart was a 1963 Lowrey that had a pair of 6V6, five 12AX7 and about 25 tone generator tubes set up on two different power rails so I think this transformer should be stout enough.

[tele_player]

years ago I picked up a forlorn 20 dollar silverface champ that I set up to match output tubes in with a spate PT just for the heater so I can power two outputs at once and I ditched the recto tube for a SS power section.
With my variac on the champ and them pumping in 4 different test tones while reading the drive signal into pin 5 I can get matches as close as 3 percent!

What procedure are you using to match tubes, and why are you using test tones?

-Robert