This amplifier was removed from a Backline 115 combo amp and installed in a custom built cabinet for use as a head. It has been tested and all of the functions are working properly.Īll of the pots and jacks have been cleaned in preparation for sale. Scoping the power supply rails, there's a bit of ripple on the +-60v but nothing that matches the crackling at the output. Power supply seems fine otherwise +-60v are nearly exact, +-35v and +-15v are within 10%, and no detectable noise on any of them. Noise at the output is ~100mvP-P, and crackling can be up to 5vP-P, maybe higher (hard to catch on my analog scope). I can see the noise when I probe Q14/18 base and emitter (perhaps it's coming from Q7A/Q7B, hmm.). Once the amp warms up enough to stop crackling (somewhere around 40☌ or ~100°f), noise at the output is around 1mv. Amp delivers plenty of power even while crackling, and fan turns on and off properly. Here's the schematic for the power amp section: gallien-krueger-backline-600.pdf. Didn't bother with preamp, since it's completely disconnected for my testing. Haven't pulled the board out yet so I haven't checked for cold solder joints. Previous owner told me that a "resistor" had blasted apart, and indeed there was a small chunk of something rattling around in the amp, but that something looked like the plastic/rubber/whatever coating from an NTC thermistor, though the two in this amp aren't "blasted apart", and the amp wouldn't function at all without them. GALLIEN KRUEGER BACKLINE 410 BLX II - Bass Amp Head - CabinetGALLIEN-KRUEGER BACKLINE 410 BLX II - 4x10 400W Bass Cabinet. No signs of anything burnt or scorched at all (though again, I haven't flipped the board - will tomorrow).Īny thoughts? I'm more used to things with tubes in them.
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