Published by on October 11, 2021
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Variac on zero, power switch off- connect power cord. 2). Connect either output to load box (load A). 3). Resistance loads open (switch in. Gallien Krueger rb Schematic Diagram. Uploaded by esquisof. Gallien Krueger rb Schematic Diagram. Copyright: © All Rights Reserved. Download as. Hello, Service Manual of the Gallien Krueger rb this is a amp for bass, there are layout, pcs, schematics for preamp and poweramp.

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You need some mildly expensive lessons before you try this on a W, especially a “beloved classic”. Not sure, but that TL chip may be out.

Please try to post it here, for future reference for others. I can email you a copy of the service manual.

I’ve done this for several of my customers who didn’t want to bother with a replacement. Opening it up R50 had burnt up. I’ve been looking over the data sheets, and seems close, but another set of eyes that’s familiar with transistor specs would be greatly appreciated. Originally Posted by hallien. Attached Files RB Preamp Each transistor base-emitter drop should be near 0.

SO if the channel switching dies, I jumper the reverb ga,lien and move its good IC to the channel switch spot.


Education is what you’re left with after you have forgotten what you have learned. The resistor-string is now For a stage-amp, I’d go crude.


Started by 3nity Drawing Board. Okay I am gonna post what I have already right now. I was working 60 hours a week for many years, so had little to no time CJ Member California Posts: However if connected wrong, the amp will burn-up at turn-on.

That is, you can still control the level of boost, as if the amp were in it’s normal state no footswitch plugged in. Also, it’s generally not as loud as it should be. Their parts department would sell you one. November 20, I’d want to do it different.

Fixed that up, things are pretty good now, but it still won’t bias right. Hey everyone, my apologies for having been absent from this particular thread for so long. The weird turn pro! You tell me whar a man gits his corn pone, en I’ll tell you what his ‘pinions is. CJ, thanks for schemmatic context regarding the topology. I can’t remember if GK has a few of those chips, but you might want to contact them to see if they still have some “reserve” stock, just for kruegre purpose.

Gallien-Krueger 400RB Service Manual

If this does not happen, the amp gets hot, idles at higher temp, gets hotter yet, and goes into “run-away”. For example, I’d rather have reverb always on that be stuck in one channel. I’m turning some of them back on. The obvious solution is: The output transistors are double-stacked so each gets less voltage. Since my last post I’ve been enjoying this amp, the output was a little hairy at power up but I’m using it in a punk band.


But will be a little rough-throat sounding around the 1W level.

GK RB schematic

Good morning, for sentimental reasons I picked up a Gallien Krueger B, it’s an earlier version of the popular RB but it’s all discreet along the lines of an old Sunn or Acoustic. When things go wrong, it gets VERY expensive fast. GK rb fan issue? Ass-uming that Q9 is exactly 1.

Can’t see what you done from miles away. Results 1 to 15 of I’ll keep replacing resistors but if anyone could help me figure out a way to keep it powered on long enough to measure some voltages that’d be a big help. I’d put these in series with the power rails.

For a fairly constant idle current in Q13 Q14, we need a bias that DEcreases when the amp gets hot. The bias voltage is dominated by Q4 Q5 current, which increases with temp, instead of a multiple of Q9 voltage, which decreases with temperature.