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Solid state amp decreased output volume

Started by Billythekid, March 15, 2016, 11:52:45 AM

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Billythekid

 Does anybody know what will cause weak/low output volume problems with a solid state guitar amp. I read it can be bad caps output transformer or transistors  etc. Any info on this subject would be a great help. I would love to get this SS amp up and running at maximum performance. Thanks

Enzo

Solid state amps have no output transformer in most cases.  Output transistors may fail but are not usually the cause of low output.  Bad caps usually make the amp hum, not sit quietly.

You can help us help you by providing the make and model of your amp, and the schematic if you have it.  otherwise we would be just guessing at your needs.

The first suspect in ANY type amp with a low volume complaint is the FX loop jacks.

Billythekid

Hey enzo, hi my amp doesn't have fx loop return send at all. It does have three speaker output jacks. Two for the two 2×10 cabs and the third for an external speaker out. The amp is 1966 67 Epiphone EA-600RVT Solid State guitar amp 100watts two inputs for bass two for guitar. Tremolo Vibrato Reverb.  I have the schematic for the amp, they are also in the Gibson Master service manual under Gibson GSS-100 set B. The problem with the Reverb is if I turn the potentiometer volume cause there is only one pot for the Reverb whick is volume, if I turn it up past 2 and 3 the amp makes a loud screeching feedback humming noise I can't explain the sound past that. I had the spring tank connected and tapp on it and can hear it but can't turn it up any thoughts.

phatt

Hi Billy,
Disconnect the tank,, both terminals. Now turn up the reverb knob. Is the squeal gone?
Also does the low volume issue you mentioned also improve while the reverb tank is out of circuit?
If so report back with results. :tu:
Phil.

Billythekid

Hello phatt thanks for getting. Back to me ive been busy. I will do as u suggested and post the results when i complete the tests.

rocky3chords

#5
Anyway greetings everyone! I'm a newbie in the forum! Cheers!

Quote from: Billythekid on March 15, 2016, 11:52:45 AM
Does anybody know what will cause weak/low output volume problems with a solid state guitar amp. I read it can be bad caps output transformer or transistors  etc. Any info on this subject would be a great help. I would love to get this SS amp up and running at maximum performance. Thanks

Gees, that's sure a lot of variables.

Quote from: Billythekid on March 26, 2016, 11:48:12 AM
Hey enzo, hi my amp doesn't have fx loop return send at all. It does have three speaker output jacks. Two for the two 2×10 cabs and the third for an external speaker out. The amp is 1966 67 Epiphone EA-600RVT Solid State guitar amp 100watts two inputs for bass two for guitar. Tremolo Vibrato Reverb.  I have the schematic for the amp, they are also in the Gibson Master service manual under Gibson GSS-100 set B. The problem with the Reverb is if I turn the potentiometer volume cause there is only one pot for the Reverb whick is volume, if I turn it up past 2 and 3 the amp makes a loud screeching feedback humming noise I can't explain the sound past that. I had the spring tank connected and tapp on it and can hear it but can't turn it up any thoughts.

Sounds like the PA worked but (maybe) not very well. To put it easy IMHO, I would first take a look at the PA section, locate the input capacitor and break the preamp connection. Do this while the amp is off. When turned on (and no smoke or LOUD hum) check whether there's loud noise / buzz when you poke it with screwdriver, and then try connecting it to some music signal. If either is true and there's no sound flaws, the power stage is fine and it's a LOT easier to isolate the trouble from there, be it preamp /fx loop or reverb (or whatever it is in there, since you have the schematic already). FWIW you can save a lot of time by knowing first that the PA section is working fine.

Anyway this is just scratching the surface.  :-\ :( Just sharing from previous experience. Cheers