Priceless tube tester

[JMFahey]

I used a 6-0-6v filament transformer because the PT only gives me 3.2v when it's hooked up to this pair of V+ in, otherwise the alternate primary lead gives me 7.2v and 800v on the filament and B+ respecitvely, and I only wanted to use the 400V option.

There's so much wrong on what you write that I doubt you'll understand me.

A "6-0-6"V transformer means you are feeding 12V to your filaments .

"The alternate primery lead" which gives you doubled voltages means something like you wired the 120V primary to a 240V wall voltage socket.

It is *normal* that both ends of a 6.3V center tapped filament winding measure 3.15V to ground.

Please measure VAC between socket legs 2 and 7, with no tubes plugged in for (their) safety.

B+ 394v before the diodes, 270v after. ???

Gives me shivers.
Hint: there's no such thing as "B+ before the diodes"

[gui_tarzan]

I used a 6-0-6v filament transformer because the PT only gives me 3.2v when it's hooked up to this pair of V+ in, otherwise the alternate primary lead gives me 7.2v and 800v on the filament and B+ respecitvely, and I only wanted to use the 400V option.

There's so much wrong on what you write that I doubt you'll understand me.

A "6-0-6"V transformer means you are feeding 12V to your filaments .

"The alternate primery lead" which gives you doubled voltages means something like you wired the 120V primary to a 240V wall voltage socket.

It is *normal* that both ends of a 6.3V center tapped filament winding measure 3.15V to ground.

Please measure VAC between socket legs 2 and 7, with no tubes plugged in for (their) safety.

B+ 394v before the diodes, 270v after. ???

Gives me shivers.
Hint: there's no such thing as "B+ before the diodes"

JM, I know you're an experienced and respected tech but please think about how you word your questions/statements in the future. I've been around here long enough, have participated long enough and have taken every bit of education and all suggestions offered to me here with humility and thanks in order to increase my knowledge to deserve a little bit of respect as I get from the other members. I'm not a beginner but I also freely admit I still have a lot to learn about how some of this stuff works. I'll ignore your tone (for now) in the sentence that I bolded and clarify what I have because it appears I haven't described my setup as well as I should have. That's my fault. And I am in the USA so my wall voltage runs between 122-125v depending on the time of day, just so we're clear on that.

The power transformer I have is out of a piece of medical equipment that used a tube that has three primary leads and five secondary leads. The primary leads are black, brown and yellow, the secondary leads are a pair of solid red, a red-yellow and a pair of green. There is no 120/240 switch on this box and right now I don't recall if all three primary leads were hooked up in the original circuit or not. I just stripped the parts and tossed the rest.

When I checked voltages on the transformer I used the black/brown and black/yellow combinations on the primary and tested the resulting red and green lead voltages on the secondary.

When using the black/brown primary leads I get 800v across the red leads, 400v from either red to the red-yellow center tap lead. I got 7.2v volts across the green pair which does not have a center tap.

When using the black & yellow leads I get 400v and 3.2v across the red-red and green-green leads respectively.

Since I wanted to use the 400v source to power the tubes' plates and grids I chose to use the black & brown pair on the primary side. That meant that I needed to use a different transformer for the filaments so I am using one that is 6-0-6 (actually 6.3-0.6.3) and am using one side and the center tap to run 6+ volts to the heaters.

So to make sure we're clear, the transformer outputs two different levels of voltage depending on how the primary leads are hooked up. You could say it's a 120/240v transformer but there was no indication on the transformer or equipment anywhere that that's what it is.

I have both red leads going to the circuit board and the red-yellow center tap lead going to a ground strip. The green leads are heat-shrinked and tied off. So at the board I have 394v AC across the red leads where they connect to the diode strings. At the end of the diode strings where they come together as shown in the schematic, I have 270v DC.

As far as the pre-rectified and post-rectified voltage question, that makes you shiver, I thought I remembered post-rectified DC voltage (before dropping resistors) as being higher than pre-rectified AC voltage normally, which is why I put the question marks there. I could be wrong, and if I am just say so without the unnecessary snarky comments and I'll take the correction and education to heart.

I used the "B+" description because whether or not that's actually what it is coming out of the transformer, that's what I've seen everyone calling it. If that's not accurate, just tell me what the correct terminology is and I'll use that instead. HT? B+? Secondary voltage? Which would you prefer?

[JMFahey]

Cool

Just let's clear the personal/tone stuff first,before getting back in the Tech side.

JM, I know you're an experienced and respected tech but please think about how you word your questions/statements in the future. I've been around here long enough, have participated long enough and have taken every bit of education and all suggestions offered to me here with humility and thanks in order to increase my knowledge to deserve a little bit of respect as I get from the other members. I'm not a beginner but I also freely admit I still have a lot to learn about how some of this stuff works. I'll ignore your tone (for now) in the sentence that I bolded and clarify what I have because it appears I haven't described my setup as well as I should have. That's my fault. And I am in the USA so my wall voltage runs between 122-125v depending on the time of day, just so we're clear on that.

That's exactly what worried me, big time.

I know you have been here a long time, in fact I had to slide the page down in my screen to check it was actually "guitarzan" who was writing this, instead of a very green noob (which you are not, at least I don't consider you such).

But what you wrote sounds so DANGEROUS that I HAD to get your attention instead of my answer being buried between a ton others which didn't see anything abnormal in your post ... which I did.

To mark those RED FLAGS which got me mad about your safety, and , please read them again literally as somebody who is not there by you , seeing what you are doing or using:

I'm not getting anything measuring V, mv or ma Weird, so far not dangerous , just indicating some lack of experience or poor build

Is it because there is no output transformer load on them? Still not dangerous but shows lack of knowledge on how a tube tester works.

B+ 394v before the diodes, 270v after. ??? Shows a serious lack of knowledge, plus you are working with dangerous voltage, not a 9V battery powered pedal.
Am I starting to see a pattern?
Which starts to worry me?
From gui-tarzan who I know as an old member,who posts regularly?
In such cases I usually go to profile page and dig out old posts to ascertain his general knowledge level.
But there's still more to read here, so for now let's see how this goes on.

Duh... I forgot to hook up pins 3.

Same results. No reading.
Weird.
Coming from a guy who measured B+ 394v before the diodes, which is impossible, starts to add to the worries.

I used a 6-0-6v filament transformer
This is gross and classic symptom of a PT used with TWICE rated mains voltage, which is DANGEROUS.

the PT only gives me 3.2v when it's hooked up to this pair of V+ in, otherwise the alternate primary lead gives me 7.2v and 800v on the filament and B+ respecitvely
This is gross and clearly points to a PT used with TWICE rated mains voltage, which is DANGEROUS.
Strike 2

If I see somebody who is reaching out to grab an Electric chair type high voltage switch by the copper blade instead of the insulated handle, I won't send him an Email or ask his secretary for an appointment, but will shout and kick his hand away from certain danger.

Doubly so if he's somebody I consider a "friend", even if an Internet friend .

Hope you see it that way now.

Take care.

[Phil_S]

JM:
I think you are being too hard on the OP who is a long time member of the forum. Sure, he's made a few mistakes here and he was not writing clearly as we might like.

What's the problem with using one outer and the CT on the filament transformer to supply 6.3V? If you were using it as a 12.3V supply, you'd still hook the primary to 120V mains. If there is adequate rating on the secondary, there should be no consequences from leaving half the secondary unused as long as the unused lead is properly insulated, which I am sure it is. If we knew the secondary was rated for 4A, then half is only good for 2A, meaning you can only test 2 6L6 at a time, but you can still do 4x 6V6. When we don't have the facts, I think it is wrong to leap to a conclusion. Maybe that FT is rated for 12A and half is still plenty for a quad of 6L6's. I like to see facts gathered before conclusions are stated. With the information we have a caution flag is appropriate, but not more.

On the PT I'm missing your point. If input is:
120 and output is 800, that's 2 : 6.6 turns.
240 and output is 800, that's 2 : 3.3 turns
120 and output is 400, that's 2 : 3.3 turns.
What is the problem supplying half the input to the 2 : 3.3 and what's dangerous about that? Maybe I'm doing the math wrong?

There's a fine line here between being helpful and not being helpful. I think it takes courage for someone to post and show pictures of something where the build quality is less than optimal and where the project isn't working. I, for one, want to encourage that. If every time someone posts a project where things aren't done they way they should be (in your/my opinion), we shouldn't jump all over the poster. In particular, if it is a long time member, you can still get the point across without the need to suggest any particular thing about the builder's ability or lack thereof.

I believe your posts are meant to be helpful and I don't think you are seeing they might have a tone that seems offensive. I don't see statements like "strike 2" as a collaborative tone.

Respectfully, I want to suggest you have much to contribute. I also want to suggest you can do that and dial it back a little bit. I think nothing will be lost and much will be gained.

[gui_tarzan]

Thank you Phil, and JM I appreciate your concern for my safety. I really do. I'm going to step back from this project for a bit, I've been work-stressed and tired the last week or so and it would be good for me to not put my hands in the box with accessible high voltage so a couple of days off might be a good thing. Then I can look at it with fresh eyes and mind.

I'll report back with what I find at that time.