Guess what?

mcblink said:
Absolutely, and we're all grateful for it.
There are some people in this world that are genuinely happy to do kind and generous things for others out of the goodness of their hearts, instead of being purely driven by profit. Those are the kind of people that I respect the most. And yeah, we're lucky to have him around.
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I'm agree. Also he is a GREAT tech. All my respect for him.
 
From age 17 to about 47, I taught myself and learned by just doing it.
Later on in life, I actually went to college and passed electricians certifications.
So there is your motivation to just learn it yourself.
You could be a good tech when you devote yourself to it.
My motivation is that I just love doing it....it never really made very much money.

If you wanted to earn a living doing that, you would need to charge $100 an hour.
Because of rent/utilities/ insurance / licensing/ book keeping / taxes/ etc...the overhead is quite a lot.
So after $100 an hour, you will wind up with $30 an hour that is the actual profit.
 
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After observing the bias level for an hour, I've seen it fluctuate from 77.5mV to 78.8mV. No lower and no higher. Both pairs together. Mostly staying right around the 78mV I set it to.
We're talking about a fluctuation over time of roughly a single millivolt....
I don't really think I should be too worried about it.
I will continue to monitor regardless.
 
Amp Mad Scientist said:
Do you know how to monitor the B+ voltage?
Leave the meter attached and see if the B+ voltage is fluctuating up and down too.
Let's see how much it drifts.

Please don't electrocute yourself.
I would feel bad if you died. But (don't worry) you will be immortalized into the Tone Rooms hall of fallen stars; remembered for your extraordinary bravery and sacrifice in the face of meandering bias drift measurements.
(like taking pictures inside a volcano, 30 seconds before it explodes)
You would not be soon forgotten, at least for a while.

I have seen things like this happen and I suspect it's caused by a slightly leaky capacitor in the bias power supply.
Since it's happening on both sides at the same time, it must be something common to both sides.
Does it seem to go up and down at regular intervals? Like it's timing out?

If you see this happening on only 1 side, I start to suspect a slightly leaky PI decoupling capacitor.

But look...
a capacitor can charge up and discharge at regular intervals when there is resistance across it...maybe that's what's happening. A very slow oscillation in a power supply.
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I have not done this, but if you would like me to I will.
After a little research, I found this:

What you want to do is measure the plate voltage (B+) from pin3 of one of the power tubes. It should measure between 450-500V.

Are you thinking of monitoring this plate voltage and cross referencing it with the wall voltage fluctuating? To see if they move together?

Or should I just play the damn thing and check it again after a bit of use?
 
mcblink said:
Am doing now.
Fuckit. It's good.
Time to forget about problems and just let er rip.

It's sounding very good. I am again impressed with the TSL
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It's good enough to play probably.
But there are some unanswered inconsistencies.
Need to trace through the whole thing to find out what causes the anomalies. There are still some questions.

It might be the meter...
It might be a tiny bit of B+ is still bleeding into the bias circuit tracks on the board somewhere.
It might be fluctuations in the power voltages.
We don't know yet.
 
mcblink said:
Me too.
I put a new PCB.
Bias drift.
I added Dr. Tube mod.
Bias drift.
Failed to identify pots themselves as a potential source of trouble.

Now I have crispy R6 on main PCB, and ruined tubes.

View attachment 63577


So today I received the replacement pots and a new matched quad of glass.
Getting stuff ready to go.
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I think you were right.
The newer issue 20 board does need the Dr. tube bias kit.
I checked an issue 20 board and (issue 20 newer was supposed to be "fixed") it had just as many problems as the earlier board.

So all of those amps that were fixed with issue 20 boards...
hahaahahhhahahahahahahah:pound-hand: sorry I hate to be the one.

There's another problem too.
Burning on the fiberglass between pins 2 and 3 of the output tube sockets (due to board insulation failure).

However, you can cut an air slot in the fiberglass between pins 2 and 3 with a Dremel tool.
That's what I did. But it will stop the frying of carbon in the fiberglass.
 
Amp Mad Scientist said:
I think you were right.
The newer issue 20 board does need the Dr. tube bias kit.
I checked an issue 20 board and (issue 20 newer was supposed to be "fixed") it had just as many problems as the earlier board.

So all of those amps that were fixed with issue 20 boards...
hahaahahhhahahahahahahah:pound-hand: sorry I hate to be the one.

There's another problem too.
Burning on the fiberglass between pins 2 and 3 of the output tube sockets (due to board insulation failure).

However, you can cut an air slot in the fiberglass between pins 2 and 3 with a Dremel tool.
That's what I did. But it will stop the frying of carbon in the fiberglass.
Click to expand...
I'm so glad that mine has now been totally gone through

Sucks to hear that the 20 board might be crap though....

IIRC, I remember you saying at one point that the Dr tube mod might be better than a new board. Seems you were right
 
mcblink said:
I'm so glad that mine has now been totally gone through

Sucks to hear that the 20 board might be crap though....

IIRC, I remember you saying at one point that the Dr tube mod might be better than a new board. Seems you were right
Click to expand...

I think that even if you buy a new issue 20 board, you may need the Dr. Tube kit.
There "are" reasons for wanting a new board (all fresh capacitors etc)

But now, I think Dr. Tube may have a 3 board minimum.
At least, I think that's what he was trying to tell me.
We tried to order 1 kit, and he mentioned 3 for a lower price. I derive that he was trying to say is that he won't sell 1 board anymore.
There may be a slight misunderstanding due to different languages Dutch VS English.

And so, right at the moment I am preparing my own bypass plan without a Dr. Tube board.
But I still need a hollow point drill if I can find one.
I'm going to try the same thing but with a home made version....
 
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