![]() ![]() 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. GALLIEN KRUEGER BACKLINE 410 BLX II - Bass Amp Head - CabinetGALLIEN-KRUEGER BACKLINE 410 BLX II - 4x10 400W Bass Cabinet. 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. Haven't pulled the board out yet so I haven't checked for cold solder joints. 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. Once the amp warms up enough to stop crackling (somewhere around 40☌ or ~100°f), noise at the output is around 1mv. I can see the noise when I probe Q14/18 base and emitter (perhaps it's coming from Q7A/Q7B, hmm.). 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. It has been tested and all of the functions are working properly. ![]() All of the pots and jacks have been cleaned in preparation for sale. This amplifier was removed from a Backline 115 combo amp and installed in a custom built cabinet for use as a head. #GALLIEN KRUEGER BACKLINE HEAD MANUALS#Simple and easy to read and use controls. Its features & specifications are identical to the Backline 350 head (search the Backline 115 & 350 owners manuals online for full details). Nice 175 watt bass head very clean punchy sound. This GK bass amp is in good overall cosmetic condition. 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. Classic USA-made Gallien-Krueger bass tone. ![]()
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