Peavey 6505 Plus preamp & poweramp seem fine but no sound

[themusic]

Trying to get more info from a thread about a year ago. At first no heater power, fixed that by cleaning & touching up
bad connections on board. got power but still no sound. sent tone thru efx return and got a strong signal thru speaker.
Also can get a faint tone thru input jack and it gets louder when channel changes. All tubes tested and good. Thanks

[Jazz P Bass]

Going in the FX return & the amp works, proves out the PI tube & the output section.
Take it to the next level.
Jumper (with a known good patch cord) the FX send & return jacks.
This will bypass the normally closed jack contacts.
If that does not help, try sending the FX send to another amp.
If that sounds bad, then the problem has been narrowed down to the preamp itself.

[themusic]

Going in the FX return & the amp works, proves out the PI tube & the output section.
Take it to the next level.
Jumper (with a known good patch cord) the FX send & return jacks.
This will bypass the normally closed jack contacts.
If that does not help, try sending the FX send to another amp.
If that sounds bad, then the problem has been narrowed down to the preamp itself.

Thanks for the input... FX to another amp sounded terrible... nothing from clean channel but pretty nasty out of lead.check tubes agan all ok.
Also checked power amp by running a nice clean stereo signal and it sounded great.

[Jazz P Bass]

Do you have the schematic?
How about a scope & a signal generator?
You will have to walk it through & find where it is failing.
For a start, by checking the preamp tube plate & cathode voltages you can tell whether or not a tube is working.

[themusic]

Thanks, yes I have them all. I'll check plate & cathode voltages tonight record them and get back.
Have a great weekend...

[themusic]

v1 pin1 436 2-0 3-0 4-23.8 5- 23.8 6-470 7-0 8-0 9-23.8 "next to P.A.section
v2 pin1 383 2-0 3-0 4-0 5- 26.3 6-387 7-0 8-0 9-0
v3 pin1 409 2-0 3-0 4-23.8 5- 23.8 6-402 7-0 8-0 9-23.8
v4 pin1 409 2-0 3-0 4-23.8 5- 0 6-453 7-0 8-0 9-0
v5 pin1 453 2-0 3-0 4-0 5-0 6-453 7-0 8-0 9-0
v6 pin1 448 2-0 3-0 4-0 5-0 6-453 7-0 8-0 9-0 Here are my readings thanks

[Jazz P Bass]

Sorry, I do not have the schematic, so this makes no sense.
If you can, please post it.
Pin 1 & pin 3 are the plate & cathode of 1/2 of an AX7.
Pin 6 & 8 are the other half.
That is what you should measure.
At first glance, it appears that your power supply is goofy.
No way should there be 436 volts on the preamp ( I am guessing)

[Jazz P Bass]

Peavey 6505+ Schematic

Found it.
I have also attached the 5150 schematic as it has voltages marked.

[52 Bill]

At first glance, it appears that your power supply is goofy.
No way should there be 436 volts on the preamp ( I am guessing)

With full B+ on the plate pins and zero on the cathode pins, I'd guess these readings are without tube in the sockets.

[Jazz P Bass]

Now that makes sense.
Try it with the tubes installed.

[Enzo]

And the 6505+ is the 5150-2, NOT the 5150.


My favorite suspect for a symptom like this would be Q7 on the 6505+/5150-2. I'd try removing it to see if the amp wakes up. (Ah, and I see the equiavlent part in the plain old 6505/5150 is also marked Q7)

[themusic]

Sorry I have not been on top of this. " Daughter getting married Sat." I really appreciate the help Once agan Enzo is right on the money.
Pulled Q7 and she woke up... thanks for everybody's help...