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 HEAD FULL#
Featuring foot switchable clean, over-drive channels, full four. Haven't pulled the board out yet so I haven't checked for cold solder joints. Superb Backline 600 Affordability, power, and diverse features place this Gallien-Krueger head in the forefront of the product line. Didn't bother with preamp, since it's completely disconnected for my testing. Here's the schematic for the power amp section: gallien-krueger-backline-600.pdf. Amp delivers plenty of power even while crackling, and fan turns on and off properly. Its a solid state amplifier and it has 1/4' connections for your input, an effects loop, a tuner out, and a foot switch. Its a pretty in depth head with a lot of controls and routing options for the recording and gigging bass player. Once the amp warms up enough to stop crackling (somewhere around 40☌ or ~100°f), noise at the output is around 1mv. The Gallien Krueger Backline 600 is a two channel, 300 watt each bass guitar amplifier head. Featuring foot switchable clean, over-drive channels, full four band active EQ and. I can see the noise when I probe Q14/18 base and emitter (perhaps it's coming from Q7A/Q7B, hmm.). Affordability, power, and diverse features place this Gallien-Krueger head in the forefront of the product line. Noise at the output is ~100mvP-P, and crackling can be up to 5vP-P, maybe higher (hard to catch on my analog scope). Power supply seems fine otherwise +-60v are nearly exact, +-35v and +-15v are within 10%, and no detectable noise on any of them. Scoping the power supply rails, there's a bit of ripple on the +-60v but nothing that matches the crackling at the output. Hi all, I've got a Backline 600 that's giving me some nasty crackling and noise, which sometimes goes away after the amp warms up, even without the preamp board connected at all - meaning it's the power amp or power supply.
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