Peavey Classic 30 - Speaker Short

[Shawnobi]

I can't seem to seem my replies for this thread?!"?

I'm seeing 360v & 370v on either end of the 390 Ohm resistor.
Something I've just noticed is that if I plug the guitar into the Efx return, I get sound! Also noticed that I can tap the reverb tank and get that noise through the speaker.

[Jazz P Bass]

The 390 ohm resistor is fine.
Moving right along, the FX return bypasses the preamp.
Did you try running a cord from the FX Send right into the FX Return?
If that wotks, you have a bad jack or jack connection.

[Shawnobi]

Yes I tried this. Guitar in the main input > jumper lead from the send to the return. No sound.

[Jazz P Bass]

Then you very well may have a preamp problem.

[Shawnobi]

Fixed! Well after all that it turned out to be a dodgy input jack. Something I'd checked and after getting it out, for something so simple I still can't quite fathom how its faulty! Nevertheless it's been swapped out and amp is working fine again.
Thank you to everyone who has taken the time to offer their help and advice in this thread. Much appreciated.

Shawn.

[NZimmerman]

Not to Hijack a thread but I'm right in the same area with a Classic 30. My 2 cents then:
1. This unit has a bad Power Transformer. It smokes when plugged into AC with outputs disconnected, simple enough!
2. Unit was disassembled. Diode CR6 is toasted. V6 and V7 Plate Voltage Run (pin7) is Blown in half between JP703 and JP712. Looks like it might have also arced to JP502 which is the filiment voltage supply. (Note) you cannot see CR6 until disassembled although you can see PCB was hot.
3. R58 Hot and cracked. 390 Ohm 5W Flame Proof (good idea) Reads as open.
4. Output transformer concerned me. Mine reads 1/2 ohm on secondary (Wht-Grn) with no shorts to primary or to chassis.
5. Out Xfmr again, Blu-Brn 180 Ohms, Red-Brn 100 ohms, Close enough
6. I still thought Out Xfmr bad until read this post. Apply 10Vpp 300Hz Sinewave to Blu-Brn yields 4.8V on CT (Red) and 4V on the secondary (into a x10- scope probe)
7. Reversed sig gen.. 208mv input into Wht-Grn yields 5V P-P (again with scope) on the Blu-Brn Pair of windings.
Concluded: OT Okay. Need a resistor and a diode. Fix the run and order a set of EL84s.
8. Checked the filiments on the EL84s and saw no ill effects from the possible arcing but the V6 tube is White at the top, cracked and obviously leaking. The other tubes have gain written on them from unknown souce and are from 60, 80, 85 (bad one) and 90. I would like to recommend to customer we get a matced set as it does not look like bias was ever adjusted for the current ones. Seems safer to order a set. I do not have a tube meter. (the things you think are of no value when you are young are all to quickly discarded :-)

[tubeswell]

Not to Hijack a thread but I'm right in the same area with a Classic 30. My 2 cents then:
1. This unit has a bad Power Transformer. It smokes when plugged into AC with outputs disconnected, simple enough!
2. Unit was disassembled. Diode CR6 is toasted. V6 and V7 Plate Voltage Run (pin7) is Blown in half between JP703 and JP712. Looks like it might have also arced to JP502 which is the filiment voltage supply. (Note) you cannot see CR6 until disassembled although you can see PCB was hot.
3. R58 Hot and cracked. 390 Ohm 5W Flame Proof (good idea) Reads as open.
4. Output transformer concerned me. Mine reads 1/2 ohm on secondary (Wht-Grn) with no shorts to primary or to chassis.
5. Out Xfmr again, Blu-Brn 180 Ohms, Red-Brn 100 ohms, Close enough
6. I still thought Out Xfmr bad until read this post. Apply 10Vpp 300Hz Sinewave to Blu-Brn yields 4.8V on CT (Red) and 4V on the secondary (into a x10- scope probe)
7. Reversed sig gen.. 208mv input into Wht-Grn yields 5V P-P (again with scope) on the Blu-Brn Pair of windings.
Concluded: OT Okay. Need a resistor and a diode. Fix the run and order a set of EL84s.
8. Checked the filiments on the EL84s and saw no ill effects from the possible arcing but the V6 tube is White at the top, cracked and obviously leaking. The other tubes have gain written on them from unknown souce and are from 60, 80, 85 (bad one) and 90. I would like to recommend to customer we get a matced set as it does not look like bias was ever adjusted for the current ones. Seems safer to order a set. I do not have a tube meter. (the things you think are of no value when you are young are all to quickly discarded :-)

Hi Neil

What about the ribbon cable between teh middle board and the extn speaker socket board? Do all the strands on that have continuity? This ribbon cable carries the signal from the OT secondary through the extn speaker socket switch, to the on board speaker. If one of those connections is broke, as those jumper 'cables' are prone to do, then secondary will be unconnected. (I pulled a C30 apart and put it back together in frustration 13 times one weekend to find this out)

Pete

[J M Fahey]

Dear NZimmerman.
Your problem is different enough to the earlier one as to deserve a new thread.
I guess you will be better served by doing so.
Good luck.

[NZimmerman]

Ribbon looks good but we will give it a resolder and ohms check. Thanks for the tip. I chased bad ribbon on a Bassman 200 last Winter. Quite frustrating.