JCM 2000 DSL no output

[sweatyk]

Thanks Dr. Gonz.........that is exactly what I did since my last post. I gave it some space and cleared my head. Being the original symptom came back I decided to start over and go back to the first reply on the post from The Dude. And he was right! I looked at the ac heater path from V6 to V5 for a break. It wasn't easy to find but I did. I didn't find a viewable break but everything from pin 6 to either tube got some extra attention. I made sure that on the socket side I made a solid solder connection to the trace pads. I hit the topside of the fuse holders. I even took a scouring pad and hit the ends of the fuses themselves. So now ALL tubes are lighting up now!!!!!!!! Now there is one more issue to deal with. It plays however the volume levels are quite low on both channels. I'm using known good power tubes that I own and his preamp tubes. Could be a tube issue....not sure. Also the power tubes got pretty darn hot after a couple of minutes playing the amp. Could be a bias issue so I will have to consider that before I return it to the customer. Any thoughts on the low volume?

[g1]

Have you tried with a patch cord in the FX loop?
Or FX send into another power amp to find out if the problem is in the preamp?

[sweatyk]

I checked V1 thru 4 in a known working amp. All tubes are good. I plugged a patch cord in the “send” jack and ran it to the “return” jack on a different amp. It sounded the same. I have volume adjustment; it is simply weak and low volume. I then plugged my guitar directly in the “return” jack and had decent volume just no control. Let me know if I have done this incorrectly. And what does it mean?

[sweatyk]

Something else I tried. As g1 suggested running a patch cord from the send to return. Made no difference. plugged into each speaker jack. Made no difference. Being I am getting sound could this be an issue with the OT? Oh and one other thing to note. As I struck a chord on the guitar i turned off the standby switch and it popped. then when I turned off the power switch the sound briefly came back and then faded. How can that happen?

[g1]

You said it sounded ok for volume plugging straight into the return. That means the power amp and the OT are ok.
The preamp is where the problem is.
For starters, check your preamp power supply voltages.
Both sides of R52,R51,R20,R21,R9.

[sweatyk]

Before I check all of this I did have one question that is probably unrelated but wanted to ask. Is it normal for the power switch to be dimly lit with it in the "off" position? I took the pic with all the lights in the room out hoping it would show up.

[The Dude]

Agree with g1. Check your power supply voltages. If those are good, I would check plate voltages on the preamp tubes. Could be that a plate resistor has started to go open. Since you've verified that the power amp is working, I wouldn't worry about the power switch light.

Edit: Nothing to do with your issue, but since you mentioned it, you should be sure to readjust amp bias when you get everything working correctly.

[sweatyk]

you said it sounded ok for volume plugging straight into the return. That means the power amp and the ot are ok.
The preamp is where the problem is.
For starters, check your preamp power supply voltages.
Both sides of r52,r51,r20,r21,r9.

r9 = 0v, 0v
r20 = 0v, .005v
r21 = 0v, 0v
r51 = .63v, 26v
r52 = 1.35v, 19.05v

[g1]

Those measurements should be DC voltage with amp in "run" mode, not standby.

[sweatyk]

That was DC and was in full run mode. Would it make a difference if the power tubes were in or out? I didn't have a way to prop the amp upside down with the power tubes in but if that is the only way then I will see what I can rig. All measurements were double checked and referenced to ground or earth.

[g1]

Ok, can you check DC at each end of R45 & R46 at the PI tube area?

[g1]

You should have high voltage at the R45/R46 junction, as you said the power amp was working when you plugged into FX return.
So somewhere between the R45/R46 junction and R52 you have a broken connection.

[sweatyk]

And just to clarify that having the power tubes out will not effect the reading?

[g1]

No, it doesn't matter if they are in or out for these measurements.

[sweatyk]

Ok, can you check DC at each end of R45 & R46 at the PI tube area?

R45 = .25V, .24V
R46 = 72v, 26.2V