The 10K resistor on the plate needs to be at least a 2W part. Plotting a load line, your 0V DC point is 28mA, but with a 1. Hi all, I have been working on a project amp with some success. The plate voltage of the first preamp tube could be a little low with the K plate resistor and 1. I haven’t had time to get into more troubleshooting this week even though I was home 3 days with the flu. But point A will probably increase to V.

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Since you’re a newb, I would advise connecting scope probes to the points you’re revsrb to test with the amp OFF. Power it up and then take your measurements.

I ain’t fussy, they sound fine to me and I have at least 40 organ pull 12au7s. That input impedance makes all the difference. My first port of call would be to check for signal at the plate 12rw7 V2A. They can get pretty messed up in shipping. The resistor grid lead and grid stopper for your reverb recovery revern are configured as a voltage divider, you will get more signal to the stage if you put the grid stopper after the grid leak.

Like a said before, increase the cathode resistor to 2.

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I’m used to thinking about voltage gain in triode stages, and not current gain, but this is running very close to, or even over max dissipation, and with an extremely steep load line. Have you checked your drive signal on the send side of the tank yet?

I dug up an old Blues Jr. The 10K resistor on the plate needs to be at least a 2W part. Log in or Sign up. By SlidePicker in forum Tubes Valves.

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Also, I don’t understand why there is a second coupling cap following the reverb control pot? I guess what I’m saying is that the boutique reverv builder may have copied a mistake For signal to noise reasons, it doesn’t make sense to attenuate the output of the tank before amplifying it, and I very much doubt the reverb tank can generate enough output to overload the following gain stage.

Jan 30, 7. Being a newb, I’m not sure what would be right. That means that either reverg 8FB tank was damaged in shipping or its input impedance is too high and blocks the signal.

There are no other ways to connect the 3, no other wires in or out! Jan 29, 3.

Checking the reverb recovery circuit with a guitar as a signal generator is a good idea. Will-Jan 29, It might be a better idea to fix that first before you try my suggestions. I’ve done this to dozens of Fender amps Most of the Ampeg amps which use this type circuit use a 6CG7 or 6SN7 driver – off the top of my head, those tubes have a bit higher allowable plate dissipation than a 12AU7 type tube but are otherwise very similar.


Did I fry something?

Got any schematics for a 12dw7 reverb? | Telecaster Guitar Forum

Measure the signal going to the drive coil side of the tank. OK, there’s a wiring mistake here somewhere! Last edited by dchang0; at I would have preferred long decay but it’s better to have something than nothing at all! The circuit is Gibson Scout revern the way except with modern tubes essentially.

I’ll take new readings all around too. FWIW this is a portion of an amp revefb I copied but wires ran under the circuit board and were not clear. For now, I’m prepared to just use the amp as is. The rest of the circuit is the same.