Where would be the best place to insert a reverb circuit into a tweed tremolux 5G9?

[Dandrix]

I didn't expect you to done with the project so soon. Usually there's a Q or two during the build process. But I'm very much like that too. Once I get a bug I'm all over it. So...

Leave the reverb down for now. I think the normal functions of the amp should be fixed before refining the reverb. And yes, I thought it might need refining. Not for squeal, but for level. I expected you to have a bit too much reverb. That's easily adjusted. What I'd really like to have the amp running properly and then "add the reverb" as it were.

You mentioned wanting to make an adjustment to the trem speed. I was under the impression that this was an already working amp (because of something you posted earlier I think). Is this the first time you're firing this up?

I'll look over the voltages as soon as I have time. I'm on duty right now. But I won't back burner you. You have my word. I know how it is when you flip the switch and it gets exciting.

thanks chuck,
The amp was fully functioning before i moved and rewired some preamp tubes moved out components and got itchy fingers and rewired input jacks and yes, volume pots and tone pot. now, i must of created myself a new problem? way to go. i will have it solved tomorrow. and yes, the reverb is pretty lush. wish my super reverb sounded that good. lol

[Chuck H]

Ok... I never did post voltages for the new reverb circuit. The voltages you posted for it look fine. The PI voltages look a little funny. The cathodes appear to be 12V higher than the grids. It should be closer to 2V (or less). Something definitely hinky there.

How closely did you follow the layout I put together? I did it to avoid the instability that might result from where things were.

[Dandrix]

Ok... I never did post voltages for the new reverb circuit. The voltages you posted for it look fine. The PI voltages look a little funny. The cathodes appear to be 12V higher than the grids. It should be closer to 2V (or less). Something definitely hinky there.

How closely did you follow the layout I put together? I did it to avoid the instability that might result from where things were.

Pretty stock I would say, what would raised voltages on the PI? Rest of the voltages looked surprisingly good. Looks to be on par with other 5g9 builders. My pwr. Trany is a Hammond 291 bx 660vct.

[Chuck H]

Your PI voltages will be a little bit higher than they were because of the change to the dropping resistor in the supply rail. It's a small change and it's not a problem. The problem is that your PI seems to be biased strangely cold. With 20V on the grids (quite low) and 32V on the cathode (quite high) The grids should be closer to 25V ish and the cathodes should be about 1.7V higher. Please re measure that because I have no idea what would cause it.

[Dandrix]

Your PI voltages will be a little bit higher than they were because of the change to the dropping resistor in the supply rail. It's a small change and it's not a problem. The problem is that your PI seems to be biased strangely cold. With 20V on the grids (quite low) and 32V on the cathode (quite high) The grids should be closer to 25V ish and the cathodes should be about 1.7V higher. Please re measure that because I have no idea what would cause it.

V2 pin1: 220 2: 27v 3: 41v 6: 102V 7: 41v 8: 41v
V3 pin1: 247v 2: 2.9mv 3: 1.9 6: 391v 7: 247v 8: 250v

Reverb section below

[Chuck H]

V2 pin1: 220 2: 27v 3: 41v 6: 102V 7: 41v 8: 41v

That's just getting worse

Now we have 14V difference one triode between the grid and cathode and on the other triode the plate voltage is strangely low and cathode and grid have the same voltage.

I can't see everything in the reverb circuit either because there are some wires under board or because you hadn't completed the wiring when you took that pic? But the component layout looks fine. Since you're taking pics, how about one that shows the PI board wiring and one that shows the PI tube wiring?

Preamp tubes rarely go bad, but it does happen and they can do all kinds of odd things. Maybe try another tube in the PI socket.

[g1]

I think it may just be the problem of measuring grids. Try measuring each side of PI with one probe at grid and other probe at cathode instead of ground.

[Chuck H]

I think it may just be the problem of measuring grids. Try measuring each side of PI with one probe at grid and other probe at cathode instead of ground.

Maybe? I don't remember having a problem with the DC voltage measurements on a PI. And the readings are so different from the first test to the next. Certainly the plate voltage measurement shouldn't read lo on one triode from one test to the next unless there's a problem.

Maybe the meter needs a new battery?

[Enzo]

Really? Never measured voltage on some FenderPI with say 60v on the cathodes and 40v on the grids? Those grids are not really at 40v. Grid and cathode are at same voltage pons 7 and 8. That ought to drag down plate voltage. Bad tube? Short at socket?

meanwhile I'd wager g1 is right, that 27v at pin 2 is a false reading due to meter impedance.

[Chuck H]

Well I can't say that I've done a whole lot of PI measurements I suppose. And I don't remember anything confusing. But then, I've been doing this long enough to know when the PI sounds like it's working right, so maybe I haven't seen this because I haven't looked. I concede.

But that anomalous plate voltage reading and the same voltage grid and cathode have to indicative of a problem.

[Chuck H]

Ok... I have an amp open on the bench so I took some measurements of the PI voltages. Sure enough the grid was lower than the cathode by over 20V. Measured cathode to grid showed 1.5V. So there you go. I learned something. Like I said, I guess it never came up and I've been fooled by seeing schematic voltages and figured those must be measured to ground from the points referenced.

Thanks gentlemen. I hope Dandrix is seeing this. There's still the weirdo plate voltage on that last reading and I think the equal voltages measured on the grid and cathode are inconsistent with what I just experienced.

[g1]

There's still the weirdo plate voltage on that last reading and I think the equal voltages measured on the grid and cathode are inconsistent with what I just experienced.

Yes, sorry I missed this (imbalance at plates). But earlier readings (post #29) were close so maybe a re-check would be in order. Dig those probes in!

[Dandrix]

new measurements:

B1 393v
B2 389v
B3 341v
B4 325v

Biasing @ 27mv
@ diode -70v

5u4: 344vac /395 dc
6v6: pin3: 382 / pin5: -26 / pin6: 388
6v6: pin3: 382 / pin5: -26 / pin6: 390

V3 Trem: 1: 247v 2: 11mv 3: 1.9v 4/5: 3.3vac 6: 390 7: 247v 8: 249v 9: 3.1vac
V2 PI 1:220v 2: 17v 3: 26v 4/5: 3.1v 6: 215 7: 18v 8: 26v 9: 3.3vac
V1: 1: 168v 2: 2mv 3: 2.7v 4/5: 3.1vac 6: 168v 7: 0v 8:2.6v 9: 3.3vac

Reverb section:
driver 12at7: 1: 388 2: 6.6mv 3: 7v 4/5: 3.1vac 6: 390v 7: 6mv 8: 7v 9: 3.3vac
recovery 12ax7: 1:214 2: 0v 3: 1.7v 4/5: 3.3vac 6: 89v 7: 3v 8: 3.7v 9: 3.1vac


it looks to me like my voltages are all good.
But, today i started up the amp and i get all white noise. pulled tubes one at a time to see where its coming from and it was the PI tube.i replaced it with a good tube but no dice. i can play guitar over the static but, its there. i have turned the reverb to zero and removed the tank for convenience sake. honestly i don't have clue what would start this to happen? failing component? your help would be appreciated

[Chuck H]

i do not no why all these pictures came in upside down, its not how i took them.

Well I guess it's how we do I'll flip them in a minute.

Strange readings now on the mix triode of the recovery stage. Hrmph. Please remeasure the reverb recovery triode.

I can't tell if we're having a problem or not because the voltage readings keep changing. A little difference between readings is normal, but we're seeing different anomalies with each post. It's like trying to catch a rolling football

[Dandrix]

no matter how i take the pictures they change on me when i upload them. i remeasure for you.
can i take out reverb tubes and play the amp straight?