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Post subject: Frontman 65r Volume problem
Posted: Sat Jan 14, 2017 5:39 pm
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Although the pot on this one is like all of them, that is, 0 = =no volume, 2 = loud, 3= unbearable, that is not the issue with my amp. After warmup, about 30 - 45 minutes. the volume drops out. Not completely, but very low. It seems to be a heat-sensitive component. I am a technician and have worked on many different types of devices, so I am pretty sure I can fix it and wanted to take a shot at it. I have the schematic, but have not been able to find a component list for the circuit board. Has anyone seen this issue and would, perhaps, be able to point me to the problem component? I am thinking a possible bad solder joint, transistor, or op-amp....some active component of some type.Thanks.


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Post subject: Re: Frontman 65r Volume problem
Posted: Wed Jan 25, 2017 9:44 am
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Intermittent problems like you describe are common on this amp. Broken solder joints are the cause.
The white 5-watt resistors are the usual culprit.
The nearby zener diodes also often break joints as well.
If you have solder experience, I would just resolder every joint in the amp to fix this and prevent further problems. Especially jacks and controls.
Opening this amp can be tricky. If you pull robustly on the knobs to remove them, you can damage them. Work them up with two screwdrivers under the knob and alternately lift a little at a time.
If the shaft has more end play than the other controls, it is damaged.
When reinstalling in the cabinet, bend the ears at the ends of the chassis to provide a little more clearance side to side.


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Post subject: Re: Frontman 65r Volume problem
Posted: Wed Jan 25, 2017 10:32 am
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TimsAudio wrote:
If you have solder experience, I would just resolder every joint in the amp to fix this and prevent further problems.


+1000!

All contemporary Fender amps suffer from the malignancy that is RoHS-compliant solder.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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