Carlsbro Cobra 90 amp dead ?

[fender62]

i was given a Carlsbro Cobra 90 series Keyboard amp but when i switch it on there's no lights, the guy who had it accidently had the volume on full power with nothing plugged in so he said when he turned it on then it went dead

[firechief]

Start by finding the fuse and report its condition. If it is bad, get another one and give it a try. If you blow the second one its probally time for troubleshooting. Folks here will offer assistance, but it might involve disasembly. Also check out this thread Carlsbro Cobra 90 and here is a web site http://www.chambonino.com/carlsbro/carlwires.html all found with a google search.

[joep1949]

Hello, İ just have bought a 2nd hand Carlsbro 90 Keyboard aplifier and want to use it for playing my guitar.
Now İ have it at home I see a lot of possibilities to put on the cables etc and also a special input on the leftside with an output?

who knows how to use these in and outputs or has a manual . İ do not want to ruin the thing because it looks great.

Pls help!

[amptech]

trouble shooting these is straight forwards..if the fuse is black don't replace it as the new one will end up the same way...in some of these amp's the pre-amp stage supply lines are fed from the ht rail via the drop down resistor zener diode supply..

use a meter to check the out put transistors for dead short's these are two npn's or 1 npn and 1 pnp o/p trannies..use 2n3773's or mj15024/mj15025 if matched pair..but it will more than like be npn 2 of..so mj15024's will do just nice..next check the driver transistors for s/c. once the o/p's have been replace next power the unit via with a 60w mains lamp fitted to the primary side this act's like a limiter in case there's a short this will save the new fitted parts. if all is well the lamp with light then dull down if it stay's on there's more trouble. once you have checked the power amps stage such as low dc offset voltage at the o/p speaker end and that there's no parts getting hot. unplug and refit the mains lead and test the unit using a low powered speaker plus keep the level down..

best of luck..