| Author |
Topic: 72 Fender Champ with problem. |
David Matzenik
From:
Cairns, on the Coral Sea
|
Posted 29 Oct 2010 11:27 pm |
|
Hi all,I have this Fender Champ which I use with a 52 Oahu Tonemaster, a 35 Rickenbacher, and a custom 8 string steel with a Rick Aiello pickup. Living in remote corners I am usually without a good amp technician. I entrusted the Champ to someone who seemed to know what they were doing. It was long overdue for some TLC so I had a cap job done, a new Jensen speaker, and some replacement chrome parts. It looked and sounded great for about two months. And I got a free Jensen T shirt! After that period it developed an unfortunate problem. As the amp heats up a hissy crackle takes over like some connection is breaking down. I have swapped out two sets of tubes so I don't think the problem is there. Any thoughts?
_________________
Don't go in the water after lunch. You'll get a cramp and drown. - Mother. |
|
|
 |
Ken Fox
From:
Nashville GA USA
|
Posted 30 Oct 2010 7:35 am
|
|
| I would take it back and give the guy a break. He can't see into the future and solve every problem that can occur with an older amp. If it worked well when it left his shop then I am sure he felt he did a proper repair job. |
|
|
|
David Matzenik
From:
Cairns, on the Coral Sea
|
Posted 30 Oct 2010 1:42 pm
|
|
Ken, that is good advise, but the cap job was done in North Carolina and now I'm living in Australia.
_________________
Don't go in the water after lunch. You'll get a cramp and drown. - Mother. |
|
|
|
Ken Fox
From:
Nashville GA USA
|
Posted 30 Oct 2010 1:46 pm
|
|
Good point!
OK, let's dig a little deeper. Does the noise continue or go away after the amp heats up?
If it continues does it go away by turning the volume down? |
|
|
|
David Matzenik
From:
Cairns, on the Coral Sea
|
Posted 31 Oct 2010 4:26 am
|
|
Back again. Ken, thanks for considering this problem which is continuous after the amp warms up. The volume does not change the hiss-crackle. Sometimes I just play with it anyway because I love the tone of the amp, but it is not something I would want to do with an audience. The crackle is intermittant, varying in its intensity, but still continuous.
_________________
Don't go in the water after lunch. You'll get a cramp and drown. - Mother. |
|
|
|
Ken Fox
From:
Nashville GA USA
|
Posted 31 Oct 2010 4:46 am
|
|
Typically that is a plate load resistor issue (the 100K resistors at the plates of the preamp tubes). Sometimes the larger B+ dropping resistors will do that as well. Best to change all those out. Rarely a cathode resistor can also make noise as well.
If you turn the volume down and it goes away that narrows it the the plate load resistor on the first preamp tube. |
|
|
|
David Matzenik
From:
Cairns, on the Coral Sea
|
Posted 31 Oct 2010 12:51 pm
|
|
Ken, I have never done any work on amps so I think it would be foolish of me to try replacing the resistors. I will file this information away and wait until I find someone with the ability. Thanks again.
_________________
Don't go in the water after lunch. You'll get a cramp and drown. - Mother. |
|
|
|
Tom Tobey
From:
Florida, USA
|
Posted 8 Nov 2010 11:47 am
|
|
It sounds like there could be another cap that is failing or one of the ones he put in is failing.
It could even be a cold solder joint somewhere in the chasis that gives way after it heats up. These are easily fixed problems. Find a TV shop and give them the schematics if you have them. They can pinpoint it in short order. |
|
|
|
