Cheap a$$ tube checker?

[booj]

6L6's generally run from about 100 to 120 plate voltage with the cathode voltage around 3.7 to 4.1 volts.
Can this circuit tell me anything about the tubes that's relevant? It's a nifty circuit, and I can find tubes in the batch (of about 50 used tubes) with really close numbers which seems like they are a match. I already know the tubes have no issues, since they work in an amp. I was just wondering if IF they looked like a match, would they be?

[J M Fahey]

That's a cheap A$$ electric chair
*Never* use directly line powered equipment.
Get any old power transformer which
1) isolates and keeps you alive
2) furnishes real world voltages.

[booj]

How is earth ground going to shock me?

[booj]

A word of explanation. The chassis is earth grounded, and this device is used in a totally controlled environment (e.g.) my shop. I guess I should have made that a bigger statement, knowing that everyone is going to immediately go and build one. (sick joke).
Yea. It's not going to pass OSHA testing for sure. The whole things a bad idea. Thanks for your reprimand. OK
NOW. Lets hook it up to an isolation transformer. Now we've got real world voltages of about 370 volts on the plate. I am using a voltage doubler. I guess that's kind of low, although I'm getting about 40 ma. current draw. Now you can beat me in the head with your criticism of the original circuit if you want to, but my question remains the same. After all, I've risk life and limb to put this post up (according to you) and I'd like an answer to the theoretical question. Can I use this information?

[booj]

Here's some of those so hard fought for results. The question remains. Anybody have any idea?

[jmaf]

If there's no point of contact between the inner circuit and the operator, there is no danger at all. Most tube testers i've seen work like that, using mains directly because there is no guitar plugged in or any interface with the operator at all. All you do is push a tube in, move some levers and test....

Of course ideally you'd have an isolated supply, but I think the danger has been overstated a bit here.

Now, that's not exactly a tube "checker" because if the heaters or the plate are in short, you don't have any means to check that, it'd just blow up. One quick idea is to add a mains fuse of 500mA or less, so if the fuse blows you know you have a shorted tube.

Another idea is to put a lightbulb in series with the mains before the first capacitor, if it lights up, you've got a shorted tube. Just my 2 cents, hope it helps.

[J M Fahey]

Here's some of those so hard fought for results. The question remains. Anybody have any idea?

Given that the image you posted is made out of 3 columns, the first one a list of power tubes and the other two a series of numbers, with no title or units attached, no, no idea.
Do you have any idea of what are you trying to measure, and why?

As a side note, a series fuse or primary series bulb would not do much here, because the power supply output is already in series with a 5000 ohm, 25W resistor which limits current to 60mA , even if you short plate to cathode with a piece of wire.
The resistor would get hot but stand it, it would dissipate around 18W.

A fuse on the "primary" (line hot) side would be useful, in fact mandatory, to reduce the danger of a house/lab fire in case a capacitor or diode shorts, but since you take pride in disregarding OSHA regulations (even to the point of stating it in writing) and even local Firefighters suggestions, I think you are on your own.

[NorCalTuna]

Isnt that thing testing as triodes? Here's a sweet idea, you could test wieners in it in tubloidial mode.
64.24 -- Electric hot dog cooker

[Prairie Dawg]

Isnt that thing testing as triodes? Here's a sweet idea, you could test wieners in it in tubloidial mode.
64.24 -- Electric hot dog cooker

A favorite of prison inmates everywhere-a/k/a a stinger. As a matter of fact I have a commercial version of this device that I got at a yard sale.

@booj, what are the parameters you are measuring? If it's cathode current across your 100 ohm resistor? I see you also don't have a function for testing any index of tube quality or as someone's mentioned shorts. You could also gear it up to test in triode mode. On the other hand if you've already acquired a good gM tester like a Hickok you'll be testing for shorts at the same time.

Truth be known, it's worth investigating. I am intrigued.

[tubeswell]

Apart from the merits or otherwise of the transformerless power supply, maybe the grid should just be shorted to ground? There's no source of blocking distortion etc to speak of, and with the grid hooked up through the 220k like that you may just get random readings. JM2CW

[booj]

jmaf,
Thanks for understanding the circuit. It does have a fuse and a power switch for safety. I should re-draw the circuit for clarity.

J M Fahey,
The 2nd column is the voltage across the cathode resistor, or t.p. 2. Sorry for the confusion. The third column is the plate voltage.
Basically, I'm trying to compare tubes to one another. They all work and have been tested in amplifiers besides the ones they originally failed in. They are all from repairs where one tube got scorched and the other unscathed, or from quads where one tube failed and the whole set was replaced. As I mentioned earlier, the device is fused. As far as disregarding OSHA standards, I remember having to take off all thje groundbreakers on our scopes at work, which allowed us to test circuits without blowing them up whenever OSHA would come in for an inspection. We couldn't get anything done while those goons were poking around. An that's just the tip of the iceberg when it comes to safety issues that got subverted to get units out. That's not to mention the things I'm asked to do by music stores/customers that want their good ol' 1950's transformerlsess amp to get back in tip top shape.
The unit is safe. It won't shock me. AND I'm the only one who's gonna use it.

NorCalTuna,
I built one of those. Don't use your good silverware to hold the hot dog. It tarnishes the heck out of metal.

Prarie Dawg'
It DOES test in triode mode. As far as indexes for tube quality, I think that was the original question. Is there anything usefull about this information? As far as comparison to many, many other tubes of the same type?

Tubeswell,
Aha! Yes I thought of that. However, it is a project yet to be finished. Maybe better filtering? (2) times 33uf/450v right now. Gotta leave room for ac inputs. The 220k for now stays.

[Prairie Dawg]

I think you could use the circuit as a matcher.