Carlsbro Cobra 90; 4 channel pa amp

This amp didn’t work. More to the point, it looked like there should be something coming out of it, but there wasn’t.

There were a huge number of these sold, probably in the ’80′s, and there are still a fair number around. The Marlin series were very similar but generally a higher power output. Whereas the Cobra put out around 90 watts rms, the Marlins were between 150 and 300 watts, which is a good whack for a non-forcedraft cooled amp. Just a chunky heatsink on the back. They were mono, bipolar amps with two speaker outs and designed to run down to 4 ohms. Much of the fabrication was done by hand with good quality pcb’s and components. Most of these components are still not difficult to get hold of, so they’re generally still repairable.

This one had been in a shed for the last ten years, or it looked like it, anyway. Two things to know about these amps and also the Marlins, is that FX send /returns and also the headphone out (where it’s got one) are in the very latter part of the preamp circuit, and if the switching gets clagged up behind the jacks, you’ll get nothing out of it. The remedy is simple and you don’t even have to open the amp up. Spray all the jack inputs and outputs  (with the amp unplugged!!!!!!!!!) get a jack plug when you’ve done that, and whack  it in and out of the sockets. This will clean up the switching contacts which is a big cause of failure on a lot of amps of this period.

If you want to do a real job on it (with the amp unplugged!!!!!!!!) take one of the end cheeks off the case and slide the top panel off. From there you can get to all the pots, and treat them to a spray out. They’ll probably need it.

That was all that was wrong with this one. It cost him £25 and he was as happy as Larry. If only they were all like that.

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