Help! - 5F2 circuit

[sclinchy]

I'm a first ttime builder (as will be evident). I finished a Fender Princeton 5F2 clone, which seems to work except that the output is a fraction of what it ought to be. I tried Gerald Webers trick of measuring the voltage at the speaker and the output would work out to about 1/4 of a watt!

I've cheked all the voltages I know of and they're all correct.

Does anyone out there have any ideas of what to check next?

Many thanks.

[Normster]

If you can post pictures of the guts and pin voltages for each tube, I'm sure the gurus here can walk you through it.

[sclinchy]

Many thanks, here's the info:

12AX7 - 1 - 224
2 - 0
3 - 1
4 & 5 - Heater (6.3v AC)
6 - 210
7 - 0
8 - 0
9 - Heater

6V6 1 - No connection
2 - Heater
3 - 399
4 - 400
5 - 0
6 - No connection
7 - Heater
8 - 23

5Y3 1 - No conection
2 - 397
3 - No connection
4 - 0
5 - No connection
6 - 0
7 - No connection
8 - 400

I can supply pictures, if you think it would help, the schematic may be found at http://www.ampwares.com/ffg/

I really appreciate this.[/url]

[Normster]

12AX7 -
1 - 224
2 - 0
3 - 1
4 & 5 - Heater (6.3v AC)
6 - 210
7 - 0
8 - 0
9 - Heater

Pin 8 should be about 1-1.5 volts. Is the NFB wire connected to the wrong side of the speaker jack?

[sclinchy]

Thanks, I just tested that again, it's about 1.7v.

[MarkB]

Check the resistor from the 6V6 grid to ground. Sometimes, people put a 2K2 resistor instead of a 220K, and the signal gets dumped to ground before it gets to the power tube.


Also, a bad tube is always possible, even if they're all new.

[sclinchy]

Thanks, but that's not it (does seem like the sort of thing I'd do, though). One other thing I've noticed, which may or may not be important is that the voltage across the first filter cap goes to 0 (or close) as soon as I turn the amp off, which doesn't seem right. I had some problems getting the heater supplies right, and when they weren't working properly, the voltage would be around 330 after turning the amp off and I'd have to drain them, which is the behavoir I'd expect.

I apologize if I'm not giving you good information to work with, and I really do appreciate the help.