tube tester question

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Re: tube tester question

Postby tone-lizard on Sat Oct 17, 2009 2:39 pm

The How wrote:My buddies shop has an Accurate Inst. #157 for 40 bux. Any thoughts on these? Worth picking it up? Is it similar to #151? Thanks.


You know, I would take it for $40 just to have it. I paid something like $20 for each of my three, and they came from the Ham Radio Flea Market. I thought $60 for three 'budget' testers was OK, until the one turned out to have a blown meter :POd:. The 157 is just a 151 with a few more 'modern' TV sockets like the compactron. I just wouldn't try and match EL34's on it and sell them on eBay bragging the tubes were tested and matched on an Accurate 157 :laff:. I did have a plethora of testers, both good and horrible, but I also had an illness. So, buy the Accurate as a cheap introduction to tube testers, but keep looking at the Flea Market (not eBay) for a nice B&K.
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Re: tube tester question

Postby PeterS on Sat Oct 17, 2009 3:44 pm

I did have a plethora of testers, both good and horrible, but I also had an illness.


:D no need to explain to us, this is the Too Many Amps bulletin board!
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Re: tube tester question

Postby jcs on Sat Oct 17, 2009 6:28 pm

Well guys, i picked up the Hickok 533A.

It lights up (the fellow i bought it from thought it didnt come on at all).

So whats next?

Now i know Hickok are complicated to work on, but the quality is evident.
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Re: tube tester question

Postby PeterS on Sat Oct 17, 2009 7:35 pm

I'm no expert but if it was me I'd first figure out whether the power supply is working.
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Re: tube tester question

Postby tone-lizard on Sun Oct 18, 2009 12:09 am

http://www.tone-lizard.com/Hickok_troubleshooting.htm

I might be a little prejudiced :wink:, but this is a real crude and basic troubleshooting 'guide'. The best part is the initial testing is done without opening up the tester at all.
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Re: tube tester question

Postby jcs on Mon Oct 19, 2009 9:03 am

Tone Lizard, thanks for the link to that page, i've looked around your site quite a bit and missed that page for some reason!
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Re: tube tester question

Postby PeterS on Mon Oct 26, 2009 5:45 pm

Humbug... I've been playing with the Hickok 539B some more, with added plate current meter.

Tested a pair of 7581 tubes (heavy duty 6L6), in the Hickok I get 40 mA and 40 mA. In my Tremolux (445 volts B+, bias voltage is at -43) I adjust them to 38 mA and 35 mA. Not too bad.

Next, let's try a pair of RCA 6L6GC. They give 49 mA and 50 mA in the Hickok. Good match, yes? In the amp, with the same bias voltage I used above, they give 62 mA and 40 mA. Adjust the bias to bring the 62mA down to 40 mA and the other tube shows 13 mA!!

SO apparently testing power tubes at 150 volts, as the Hickok does, is USELESS. Must get my hands on that AVO 400 volt tester...
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Re: tube tester question

Postby jcs on Mon Oct 26, 2009 8:16 pm

FWIW, i use a tester to screen for shorts and mutual conductance.

I always match for current draw in a live amp with a Weber Bias Rite, never had an issue doing it this way.

My main concern is run away current draw and shorts, these are the most important things imo.

Am i wrong?
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Re: tube tester question

Postby PeterS on Mon Oct 26, 2009 9:05 pm

No, I think you're right.
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Re: tube tester question

Postby PeterS on Tue Oct 27, 2009 7:11 pm

Progress, borrowed the AVO Mark 4, which is both mysterious and beautiful. Tested the RCA 6L6 pair that match at 150 volts in the Hickok but don't match at 450 volts in my amp. The AVO goes to 400 volts but I just used the 350 that is the chart setting for testing 6L6... currents read 43 mA and 53 mA, showing the mismatch rather nicely.

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Re: tube tester question

Postby pckpat on Tue Oct 27, 2009 9:43 pm

wow-i love that look-real 50's sci-fi,shades of ed wood :lol:
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Re: tube tester question

Postby PeterS on Tue Oct 27, 2009 10:27 pm

It has those big curvy solid handles, great example of form-meets-function. The knobs turn with a pleasingly solid click as well. The Avo meters are rather stylish too:

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Re: tube tester question

Postby Baron Von Machinenmann on Tue Oct 27, 2009 11:07 pm

PeterS wrote:Progress, borrowed the AVO Mark 4, which is both mysterious and beautiful. Tested the RCA 6L6 pair that match at 150 volts in the Hickok but don't match at 450 volts in my amp. The AVO goes to 400 volts but I just used the 350 that is the chart setting for testing 6L6... currents read 43 mA and 53 mA, showing the mismatch rather nicely.

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Re: tube tester question

Postby tone-lizard on Wed Oct 28, 2009 2:21 am

PeterS wrote:Progress, borrowed the AVO Mark 4, which is both mysterious and beautiful.
Image


How did you find one in Canada? :shock: I feel lucky finding any Hickok, and you find an Avo? I musta done sumthin bad in a previous life.
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Re: tube tester question

Postby PeterS on Wed Oct 28, 2009 4:51 am

Well, I work in the physics department of a big university, there's about 5 tube testers that I know about. A lot of the guys in the department back in the day were English, that might be why we have an AVO. I also have an AVO meter, although it's in rough shape. I'm only borrowing the AVO tube tester, whereas the Hickok is more or less mine since I rescued it from the garbage. We are about to have a building renovation in which a lot of obsolete old junk gets tossed, so I am angling towards creating an opportunity to move the AVO in the direction of the dumpster and then rescue it from an awful fate. In a way this stuff is small potatoes compared to the value of scientific instruments that get tossed out once the one person who knows how to use them retires.
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