Sho Bud single channel amp

[Jerry Meek]

Does anyone have an idea The amp was working perfectly when I shut it off when I turned it on it started a loud buzzing noise I shut it off and checked the speaker it was fine haven't looked inside yet because I don't know what to look for. I don't know of any credible repairman in Colorado that has experience with SHO BUD amps I don't want anything changed I loved the tone over all the different amps I've owned My Christmas tree sounded as good but during the Franklin era I got stupid and sold it. If I could find aD130f JBL 4 ohm speaker t6hat sounded like it's supposed to I would be interested in putting it in one of My Evans amps. but I rteally want my SHO-BUD fixed.

[Jerry Meek]

Apparently the previous owner either did or had work done on it that a lot of empty spaces on circuit board . He fixed the speaker noise but according to his analyizing Eqpt. it was only putting out 5 watts don't see hows thats possible before the buzzing issue it was quiet as a mouse and plenty of volume between 2 and 3 volume. If anyone has an idea about it I would appreciate hearing . It seems there different schematics for the single channel just wondering if one of included removing things off the circuit board. I know very little about electronics and I know it.

[J Fletcher]

I think they are a pretty standard solid state amp , and a competent repair person could sort it out .

[Ken Fox]

I’ve got one coming for repair

I found the schematic
with a Forum search

[J Fletcher]

Looks pretty much like the Xmas Tree amp , minus one channel .
Mine had very low output when I got it , the culprit was the electrolytic cap that connects the 320 ohm resistor to ground , at the driver stage . Part of the feedback circuit . The cap must have dried out over the years , and was acting like a resitor in series with the 320 ohm resistor . Result was way too much negative feedback and the driver stage couldn't develop enough signal to drive the outputs .
Jerry

[Ken Fox]

Good call on that. Not sure what the amp issues are yet, he has not told me

First thing I d it check all electrolytic caps with and ESR meter. Those are always likely suspects for trouble.

I bring up any unknown solid state amp thru a dim bulb tester to make sure it does not have shorted outputs.

[Jack Stoner]

Early 70's when I would get in a solid state amp with no output usually the output transistors and driver transistors would all be bad. No protection back in the early days of transistor amps.

[Jerry Meek]

I thank you Ken I gave my Amp guy the go ahead he Completely re did it and even added a bias control was worried he might have changed the tone . but he did a bangup job, I do appreciate the schematic will try to download a printed copy. Jerry