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

[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]

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.

[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]

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]

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]

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]

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]

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.

[Dandrix]

chuck,
fired up the amp today, had some debugging to to do. still got some issues to correct like tone pot controlling the volume (miss wired something)
trem. works! would like to better it if possible? slower speed etc.... and then the reverb..... its alive! it works pretty good up to about 5 on the dial then, it turns into white noise (static) by the time it gets to 12 it feeds back in typical fender reverb fashion. high pitch sequel, my reverb unit is out of the cabinet and on my floor at the present. got any ideas to remedy this new reverb? left voltages below, time to grab a beer!

All heater voltage 3.3 -3.1 vac
bias at 27 mv (JJ rated @ 29mv)
B1: 393 / B2: 391 / B3: 349 / B4: 332 added filter cap for preamp

5U4 344vac / 398vdc
6v6 pin1: -26 /pin3: 386 / pin 6: 392
6v6 pin1: -26 / pin3: 384 / pin 6: 391
V3 tremo. pin1: 288 / Pin2: 5mv / pin3: 1.7v / pin6: 391 / pin7: 293 / pin8: 295
V2 PI pin1: 227 / pin2: 20v / pin3: 32v / pin6: 217 / pin7: 21v / pin8: 32v
recovery 12ax7 pin1: 223v /pin2: 0 / pin3: 1.7v / pin6:230v / pin7: 0v /pin8: 1.7v
Driver 12at7 pin1: 389v /pin2: 7mv /pin3: 7v / pin6: 389v / pin7: 0v / pin8: 7v

V1 pin1: 173 /pin2: 2.2mv / pin3:2.7v / pin6: 172 /pin7: 0v / pin8: 2.7v

i have not had a chance to look over readings but, i was not sure what your were shooting for voltages on the reverb side of things?

[Chuck H]

Pretty sure you only need to cut across the exposed copper portions. That way you can just dab some solder across then to restore the ground. Just the same, mission accomplished

[Dandrix]

Hi chuck,
With reference to the instruction of cutting mod reverb ground trace to isolate ground. I cut trace so, metal rivets no longer have continuity if small mounting board. As pictured


I was not able to find instructions? accidentally deleted your instructions in our PM

[Chuck H]

Yes that is the usual consensus... but it is very subjective. Neil Young and others might object. That’s why I asked if he had ever tried it. If you really wan to add it last on an old school amp one can use the old Maestro Reverb approach where the reverb unit parallels off of the speaker out and is essentially an extension amp with reverb and a speaker.

True that about subjective. And yes, the Maestro type circuit is what I've been talking about here in other posts. I think Mojotone actually sells a SS reverb amp like this (it does have a tank and not a "brick" I think) that can be used with any amp. I built a tube reverb amp for a guy once years ago. I really like that arrangement.

EDIT: Ok, it was a few years ago I saw the Mojotone SS reverb amp. It seems they bumped their game and now only sell a tube version. So it's a lot more costly.

[olddawg]

Agree! But it's definitely more of a "host amp is run clean" kind of thing.?. Dandrix has indicated that he's a rocker and so I assume he's crunching it up. On board is a little better for that. And, of course, my recommendation of a dedicated post distortion reverb amp is best But that's bee's knees. I built one for a customer and "I" don't even have one. But I used it with my own rig (because that what I have, right?) before putting my stamp on it and sending it out. Always best to incorporate reverb as late in the circuit as possible if you intend to clip anything. JM2C

Yes that is the usual consensus... but it is very subjective. Neil Young and others might object. That’s why I asked if he had ever tried it. If you really wan to add it last on an old school amp one can use the old Maestro Reverb approach where the reverb unit parallels off of the speaker out and is essentially an extension amp with reverb and a speaker.

[Chuck H]

Alrighty. I think I got this right though I've been a little foggy lately. I'm no doctor but I'll guess it's all the drinking

But seriously, this should be correct. Notice that the arrangement keeps the signals moving in one direction (for the most part) rather than going back and forth over later circuits. I used the original 5g9 layout board as a template for clarity. I know your amp isn't layed out exactly the same, but this should give you a consistent reference point for the circuits. Like I mentioned, you'll need to move some board components to locate the reverb build space where it is on this layout. I know the proportions are a little off too. Unavoidable, but it should be close. I layed out the additional circuits on a 7x3 eyelet space like you posted.

[Chuck H]

Tell what you think? I could add the extra filter cap to the dog house? It looks like I could squeeze them all in there seeing the F&T’s are so small. Maybe, locate the One 5.1k/3watt resister at B3 Cap and the 5.1k top side on the board ( maybe next to biasing section)?
[ATTACH=CONFIG]57994[/ATTACH]

Too many wires running back and forth to get to the resistor and back. Why not just put the resistor on the terminal strip? Raise it off the cap and it'll be fine. It's the last resistor in the chain so it won't get that damn hot. So if you're going to put that cap in the doghouse just make sure you run the ground to the preamp and NOT with the other caps.

I'm posting the layout in just a few minutes. The layout shows the added filter at the end of the board where you originally proposed, but it doesn't have to be there. It would make for a shorter lead though and that's always best. Adding length to that ground lead adds resistance and that invites parasitics. Since the preamp is the most sensitive to this I vote for your original location.