Gallien Krueger 200RB

[MarkusBass]

I'm looking for Gallien Krueger 200RB schematic. This is vintage bass amp from 1981. It seems that the amp I have has some power supply problems but I'd like to see the schematic. It sounds like it has chorus effect :-) .

Mark

[nickb]

I only have the preamp p/n 60040 also used in the 115BC. I think the 60039 might be close to what you need.

gk_60040.pdf

gk_60039.pdf

[MarkusBass]

Thanks. It looks very close to what I have. I'll check it in the evening.

[J M Fahey]

Weird, the power amp has no short circuit protection.
Given the poor quality of most plug to plug cables (after some time of use) that sure looks like Russian Roulette.

[MarkusBass]

Thanks Nick. The amp uses exactly the boards.

Apart from missing short circuit protection, the amp is manufactured very well. The amp is about 35-year old but inside it looks almost like new. It actually fixed itself . There are only three wires between the power amp/supply board and the preamp board. The wires are +15V rail, -15V rail and signal (hot). The ground connection is missing - it is connected through the enclosure. And if the screws in the enclosure are loose, there is no good ground connection. The low power supply starts pulsating and as a result the amps sounds like chorus effect.
Juan, the amp has 0.33R/5W resistor on the output. Maybe it forms a short circuit protection. In case of the shorted output, it will burn . Anyway, this amp was used for 35 years and nothing wrong happened to it.

Mark

[g1]

I believe a factory warranty mod for that was to run a ground wire from a front panel jack (input?) to a rear panel jack (spkr?).
Not 100% sure about this model but I think it was for all early RB's, and maybe some RL or ML also?

[doctor]

I believe a factory warranty mod for that was to run a ground wire from a front panel jack (input?) to a rear panel jack (spkr?).
Not 100% sure about this model but I think it was for all early RB's, and maybe some RL or ML also?

Here are the schematics.

[MarkusBass]

Thanks guys. You really helped me. G1, I applied the mod suggested by you and it decreases hum a little bit. I also switched the amp from 110V to 230V (the owner didn't know that the amp can be easily switched to European voltage).

Mark