Low power/distortion Hot Rod Deluxe

[lowell]

This amp has good signal out of the preamp out. I tried swapping in new tubes, I've checked the bias supply and get -45v to -55v when adjusting pot on pin 5 of power tubes. Phase inverter has these voltages:

1-272
2-27
3-42
6-260
7-28
8-42

There is 466v on plates and thereabouts on screens of both power tubes. Cathodes are indeed grounded. I suspected a bad B+ filter cap and when I tested one it was indeed bad so I replaced it. Now there is still very low volume and distortion when I crank the clean channed volume all the way up. I'm left thinking the OT is bad but I measured the primary and get 58ohms on one side and 62ohms on the other. I disconnected the secondary from the output jack and measured for shorts to the core and nothing. Is there another test on OT or are these results sufficient to think the OT is fine?

[Diablo]

Are you sure the speaker cable is plugged into the correct output jack?
If it's in the wrong one (extension speaker), you'll have very low output and lots of distortion.

[lowell]

I'll check that tomorrow... why is that?

[Enzo]

Because the main speaker jack has a shorting contact on it that shorts across the output when nothing is plugged in. The extra speaker jack does not. SHorting across the output of most amps usually results in low output and lots of distortion.

[Diablo]

Also, the jacks aren't labeled - a brilliant move by Fender...

The speaker plug should go in the left hand jack (as you face the rear of the amp).

[tim]

Also, check the 82K and 100K plate resistor on the 12ax7 that drives the power tubes...when one opens up, it's usually the 82K but not always. if one of those opens up, then it will give you the problems your describing...

[tim]

I re-read your initial post and realized that if you are getting 270ish volts on 1 and 6, then the plate resistors are probably ok...carry on.

[lowell]

wow what an idiot move on my part. spent hours searching for the problem. thanks yalls.

it's funny cause the amp DID have a fried plate resistor on the PI when it came in. I replaced it and a bad screen resistor on the power tubes and then plugged the speaker cable into the wrong jack, and it seemed the original problem was there but WORSE. ha!

[tim]

lowell,
If it's any consolation, I have seen these amps come into me with the same problem, several days out of the box with the same complaint...customer swears up and down that they never touched the plug (and I believed them, heck, they just got the amp and they said it was like that out of the box)...the only other scenario is that it had to have come from the factory that way...
Go Figure...I wonder how the factory did final test?

[Diablo]

lowell,
If it's any consolation, I have seen these amps come into me with the same problem, several days out of the box with the same complaint...customer swears up and down that they never touched the plug (and I believed them, heck, they just got the amp and they said it was like that out of the box)...the only other scenario is that it had to have come from the factory that way...
Go Figure...I wonder how the factory did final test?

So how much do you charge 'em to plug the cable in the right jack?...

[tim]

a half hours labor...by the time I fix it, do the paper work and get it back to the customer, it's taken at least that...I've never had a warranty claim rejected for that work.

[Enzo]

I also charge a half hour for that.

Customers are not paying me for sweat, they are paying my shop to have the skills and knowledge to solve their problem. If it were truly so simple, they would have seen their mistake and moved their own plug. The fact it was easy for me was born of my exp-erience with the system.

[tim]

I also charge a half hour for that.

Customers are not paying me for sweat, they are paying my shop to have the skills and knowledge to solve their problem. If it were truly so simple, they would have seen their mistake and moved their own plug. The fact it was easy for me was born of my exp-erience with the system.

Exactly right and I don't have any problem charging the manufacturer for their errors either, in this case Fender.

[pila]

It's worth at least half an hour. I believe a customer would be glad to pay that fee, even if it was his older amp that was plugged in wrong.