Mojo Princeton Reverb

[jefe]

I built a Mojo Princeton Reverb. All is well except I am getting almost double the voltage out of my rectifier tube. The tube is a 5ar4.
Any ideas?

[txstrat]

Do you mean ALL voltages are double as high?
What's your wall voltage? Maybe the primary side has to be rewired.
If your wall voltage is 230vac and you wired the PTs primary for 120vac the secondaries all are roughly double.

[jefe]

txstrat,
Thanks for your reply.
My wall voltageis 120v. Yes all my voltages are just about double as high. Ex: pin 3 on my first 12AX7 has about 7-8v.
The amp seems to be working with the exception of it sounds very overdriven without bringing up the volume past "2".
Does this seem correct?

[überfuzz]

Have you measured voltages (AC) in your transformer?

[jefe]

327 on both red wires to the 5AR4; 6.3 on the green wires for the lamp and volt heaters; and 885v on the yellow wires going to the 5AR4.

[überfuzz]

Ok, I'm not familiar with the scheme used in a PR but you need to check the specifications of the power transformer and the voltages in the circuit scheme. 885 VAC sounds unhealthy high.

[txstrat]

I don't know how familiar you are with the tube pinout.
The little nose on the octal power tube sockets (or rectifier tube socket) is in between pins 1 and 8. When this little nose points to you, pin one is on the left. The other numbers follow clockwise. (when you look down on the tube socket inside the chassis)

Pin 1: no connection
Pin 2: yellow
Pin 3: no connection
Pin 4: red
Pin 5: no connection
Pin 6: red
Pin 7: no connection
Pin 8: yellow
Pin 8 should read around 450 volts, more or less.

Have you disconnected the wires and measured the voltages on the transformer leads?

[überfuzz]

Silence, you're not getting Zapped I hope...

Try to narrow it down a bit by doing this:

1. Make sure you have a functional rectifier tube.
2. Measure (AC) the taps from the power transformer, with normal load.
3. Check the filter. Try measuring pin 3 or 4 on the power tubes. If you're getting AC there the filter could be bad, busted or bad wired.
4. Check all wiring. If there's a bad wire somewhere in the amp there's probably not sufficient load, some where in the amp... That can give unsuspended voltages.

[jefe]

Thanks for the input, everyone!
I have some time this weekend. Im gonna try to put some of these to use. Stay tuned. . . .