Fender Amp Repair

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Old 12-01-07, 02:28 PM
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Fender Amp Repair

I have a fender solid state guitar amp that's squealing like crazy when I turn the volume up. Even with no guitar plugged in. The squeal changes pitch as the knob is turned.

Any ideas what might cause this?
 
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Old 12-02-07, 03:08 AM
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Is the input jack loose, or was it loose and you tightened it? A loose or broken ground at the input jack will cause this oscillation. So will a failed cap and/or loose ground on the volume or tone controls. That's really all you can probably check. Other causes are tougher to find.

Fender is very good about making their schematics available, complete with test points. If it's a digital modeling amp it's going to be a whole lot tougher and may have to go to a factory-authorized tech. What model is it?

I won't ask why you're playing guitar through a solid state amp. I'm a tube guy. Got me a little Fender Hot Rod Deluxe for my Strat and 335.
 
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Old 12-02-07, 07:09 AM
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The input jack has been replaced before. My daughter would accidentally yank the cord with her guitar. I've replaced it twice but the last time I fixed it it worked fine. I tested the jack with an ohm meter and it seems to be okay. I will check for a bad cap or ground on the tone controls as you suggested.

I did get a schematic off of the fender website but I didn't notice any test points. I'm not too good at reading schematics. I'll look closer. It's not a modeling amp, its a Frontman 25R.

I bought it to use as a practice amp a long time ago. Now it's my daughter's amp until I can afford to get her a nice tube amp. I use a Marshall JCM900 dual reverb combo with my les paul custom... All tube and I LOVE it.

I used to have one of those Hot Rod Delux amps. Boy do they scream!! I love the dual drive channels. Their so thick and creamy! And the clean channel is the best. My marshall's clean channel doesn't even compare. I regret selling it.

Thanks for the advice. I'll check those things out and report back.
 
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Old 12-03-07, 04:31 AM
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My HRD schematic has tiny print next to certain junctions that lists the voltage that should be there when you measure with a multimeter with one lead grounded.

A tube amp has potentially lethal voltages inside. A solid state amp is safer, but take the necessary precautions when measuring near the power supply.

The Marshall JCM800 50w half stack is my all-time favorite amp for dirt, and the Roland JC120 for clean. My back won't allow me to carry either one to gigs anymore.
 
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Old 12-04-07, 10:02 AM
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Is it more of a feed back squeal? If so , maybe the problem is with your gain. I know on my music equipment with nothing plugged in I can get it to squeal by just raising the gain up high. Maybe its up all the way and your knob is pooped out.
 
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Old 12-05-07, 02:59 PM
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No... It's not like feedback. It goes from a low rumbling of the speaker to a high pitched squeal as I turn the gain volume from 0 to 10.
 
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Old 05-20-09, 11:30 AM
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Question Fender Bassman 100

Hi.

I have had this amp for at least 6 years. I was in two bands with it and played numerous shows with the volume cranked.

Some months ago, it started making some static-noise and then quit producing volume altogether.

The light still appears, so it is drawing power. I guess it can't be a fuse or power-supply issue.

There don't seem to be many (if any) service centers locally for amp repair.

I would like to fix this on the cheap, rather than buy a new one or pay big bucks, for obvious economic reasons.

Anyone got any pro-tips for me?

Thanks in advance!

 
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Old 05-21-09, 06:25 AM
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Is this the newer solid state version? Try putting a guitar cable between the effects send and effects return. Sometimes the contact points in those jacks get gunk on them and won't pass the signal internally.

If it's an old tube model, when was the last time you replaced the tubes?
 
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