Gallien-Krueger 700RB

[MarkusBass]

I'm looking for schematic of G-K 700RB bass amp. What is important is that I need power amp version 0250-A5. It is different from previous versions - it has 2 separate transistors on the input instead of one double transistor. What is also important is that several resistors have different values (or were removed). In the amp I have there is a problem with the input stage (a thump when turning on the amp)and with the output (-0.7V on the speaker).

Mark

[doctor]

I'm looking for schematic of G-K 700RB bass amp. What is important is that I need power amp version 0250-A5. It is different from previous versions - it has 2 separate transistors on the input instead of one double transistor. What is also important is that several resistors have different values (or were removed). In the amp I have there is a problem with the input stage (a thump when turning on the amp)and with the output (-0.7V on the speaker).

Mark

Hi Mark,

All 700RBs have one double 2SC3381 transistor, only 700RBII has what you need (two low noise 2SC2240). I think that this is your case.

With regards to turn-off thump problem there is solution from GK.

Good luck.

[MarkusBass]

Thanks Doctor, this is what I need. It's 700RB-II. There is a resistor missing from Q2A base to the ground. I was hoping that this is a mistake during assembly of the amp but looking at the schematic it's not. The input stage does not work correctly and I thought that this is due to the missing resistor.

Mark

[Enzo]

"Missing" parts are usually just changes. If it were the cause of the problem, the amp would never have worked from the start.

[MarkusBass]

The amp had thump when switched on from the start. No one measured voltage on the output (-0.7V) so I'm not sure whether this is a failure, or feature :-). Apart from this, the amp works correctly.

Mark