The Amp Garage

For a negative output the direction of the diodes and capacitors must be reversed.

Peavy triumph 120W PT: US version is: #70518719 European version is: #70518705 TAD has a replacement (for 160€!): Primary: 0V Black 220V Grey 230V Brown 240V White Secondary: 195V Red 0V Pink 195V Red 23V Orange 0V White 23V Orange 6,3V Yellow 0V Yellow They use the first secondary without the CT (f...

Why can't the voltage be taken from a different i.e lower 'node' further down the dropping string B+ chain?

Shure. TAG member lovetone did it that way...

MHartmann´s has the cathode follower too.

The AN Wonderland has a common power amp circuit.

A cathode follower is a current gain stage. IMO it avoids overdriving the power tubes and keeps the sound "clean". I´m shure here are guys who can explain that in detail.

Marcus, in the original #002 circuit there is the "PT driver gain stage". This is a normal 12AX7 valve. Plate voltage is taken from the screen resistor node (~450 VDC). Crucial in that part of the circuit is that the grid and cathodes (it´s designed as a cathode follower) have a negative potential o...

Wow, Erwin. That one looks great.
Superb tweed cab job.

Thanks for the additional information concerning the feedback thing.

Lars

Looks good. Fast progress.
You placed the standby switch previous to the rectifier diodes and the reservoir caps. Why? The eyelets for the HV, Bias winding and relay power look very close to each other. Make shure they don' t have contact.

Lars

Hello jigibao, welcome to the ampgarage. It's all here, but sometimes hard to find.
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SMS #002
http://ampgarage.com/forum/download/file.php?id=23633

ODRS #013
http://ampgarage.com/forum/download/file.php?id=30840

Lars

So I guess all you had to do was ground the shield on the send cable, yes?

Exactly!

Hello Erwin, thank you.

Dimensions are:
66 x 21 x 7 cm

Lars

Thanks Martin! there was no ground connection from the amps send jack sleeve to the ground end of the input transducer (black cable coming from the coil). The sleeve of the tanks input jack is insulatet to the chassis. Only the return jack of this tank is not insulated. They do it that way to preven...

Ok. Fixed all the problems. Reverb problem was just a bad cable with missing ground connection to the input transducer. For the FET I followed the instructions from Martin Manning. Increased the voltages, fixed a bad solder joint at the source resistor an replaced the source bypass cap with a 22µF. ...

Input impedance of the unit is 8 Ohm - I thought ~1 Ohm DC resistance would be ok, but that seems to be wrong...

Unfortunately I haven´t a substitute. I have to order one.

Thanks Martin. Yes, 220k/8k2 with B+7 361VDC was a bad calculation for the voltage divider. Of course I remember your instruction for biasing the FET circuit with the 2 9V batteries! I´ll do that first. Then I´ll stick a 470k in parallel to the 220k. The reverb issue bugs me even more. I grounded th...

Shipping costs are already included (GLS to Germany). I´m aware of the less expensive electronic parts in the easter part of Europe and I have a hight estimation on their products. Unfortunately often their internet performance (if they have one) is not in english. 50€ for a brand new PT is unbeatab...