The Steel Guitar Forum

I just picked up a Shobud Amplifier. The label on the back says Model 7832, manufactured by Baldwin Piano Co.. It's a two channel "Twin Transistor". It has eleven side potentiometers on the front and a power meter on the right side. I'm assuming it's from the late 60's to early 70's. Can anyone tell me anything about this amp? I may also need a schematic and parts if someone can lead me in the right direction.
It works but has a hum. If I turn the reverb off, the hum goes away. Also, you can only play notes/chords in upper frequency ranges. Low frequencies make it sound like a Mack truck in low gear. Breaks up real bad.

Thanks,
Carl

Carl,

Jimmy Campbell worked for Sho-Bud in Nashville from 73-76 (in the good old days). He has schematics for Single Channel and Dual Channel Sho-Bud amps. You can use the link below to send him a e-mail. He put a set in the mail for me a few days ago.
http://steelguitarforum.com/Forum11/HTML/002722.html


Bob


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Thanks Bob. Just talked to Jimmy a few moments ago and he's sending me a schematic.

Carl

Carl,

I just got mine in the mail on Friday. Looks great. He also e-mailed a very nice picture of it.

Bob


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<FONT SIZE=1 COLOR="#8e236b"><p align=CENTER>[This message was edited by Bob Lawrence on 08 September 2002 at 06:16 AM.]</p></FONT>

I got mine Monday. Unfortunately, it wasn't the one for my amp. I'm still searching. However, I did establish a nice rapport with Jimmy. Thanks for the reply.

Carl

Do a cap job on it and if it's a spring reverb/tank operation, check the shielding on the wires to and from the reverb tank.

These amp generally need new filter caps for rock solid bass performance, if they still have the original units. Although I have a different model Sho-Bud amp than yours, I think my B+ filter caps are 5000uf@63 volts. The value is usually printed on the can. 4700uf, which today is a more commonly seen value, will work in an almost indistingushable manner. This will get you started, but I'd also replace all electrolytic caps in the amp and there are alot of ceramic caps that could be upgraded to better sounding devices. Replace all drifted resistor as well. Certainly, replace all that are 10% from stated value and some critical ones should be 2%. This will remove that 'tired, worn out' sound from the amp.

Bob M.

Jimmy sent me some copies and wouldn't take anything in return. I feel a little awkward about getting something for nothing, so let me sing his praises, what a wonderful person he is.

Thanks for the reply Bob. The B+ caps are 4000uf @ 60 V. I have found a few transistors (SFC5865, 7223A) that are bad. I still need to find a suitable cross for them. I believe they may correct the reverb problem and the lack of signal to the ammeter. I also found and corrected countless cold solder joints. The electrolytics on the board have already been replaced. B+ caps are next because they have visible evidence of leakage. Once I get all that cleared up, I have some slide potentiometers to replace. That's going to be the tough one. Haven't been able to find any that aren't PCB mount. The pots on this amp attach to a metal plate with tabs on the back of the pot. I may have to reverse engineer. I may have failed to mention that it has a sweet JBL K-130 in it. Even if the amp was a loss, the speaker was worth the investment.

r,
Carl

Does anyone know where to get the slide controls? I have one of these amps and all the sliders are broken off even with the face.
Jerry

Jerry: I've searched high and low without any luck, so far. I thought about shortening the standoffs that the mounting plate attaches to. That would allow the broken slides to protrude through the face of the amp, hopefully enough to get some knobs on them. If nothing else, they'd be accessible.

r,
Carl

Or, could you fabricate a new face plate and have regular radial pot controls installed?

This model ShoBud amp was subject to this design flaw, historically.

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Jerry: My amp also had all slides broken off flush with the face. However, I tried my idea about shortening the standoffs. It works beautifully. There's more than ample amount of slide coming through the face of the amp to add slide knobs. Now all I have to do is find some knobs that will fit the thickness of the slide. They're not standard because I've tried several new ones and they won't fit. At least I can control everything now.

r,
Carl

Great idea Carl, thanks, if I can come up with some slider knobs I'll let you know.
Jerry