Carlsbro merlin pa 150 head amplifier....Fault..dead...
I've not seen one of these in years,..I was ask to repair this amp as it had been in store for some time and left to rot!!...
So after giving the outer casing a good clean up and polishing followed by dismantling to start on the repair. for those of you who have serviced these amps will recall how quick they come apart plus the simple lay out of both power amp rear chassis and front chassis plus the reverb tank that sit's in the middle of the cabinet.
The main problems is as follows....main rail fuse's blown..power transistors s/c.. driver's transistor s/c and emitter resistors o/c plus cracked print/dry joint's on front pre-amp pcb and scratchy pot's due to wear and tear..not for getting these amps are 30+ years old! built to last and once serviced will last for many more years...
The power stage and be traced out very easy or if you can get hold of the schematic it's plain sailing...a quick tip is ... the cobra power out stage is the same design so can be used to aid repair... such as long tail pair/driver bootstrap cc and the o/p transistors... pre-amp is just a repeat of one channel followed by reverb circuit..
So after replacement of parts and more tidying up this amp was ready for action....
I've not seen one of these in years,..I was ask to repair this amp as it had been in store for some time and left to rot!!...
So after giving the outer casing a good clean up and polishing followed by dismantling to start on the repair. for those of you who have serviced these amps will recall how quick they come apart plus the simple lay out of both power amp rear chassis and front chassis plus the reverb tank that sit's in the middle of the cabinet.
The main problems is as follows....main rail fuse's blown..power transistors s/c.. driver's transistor s/c and emitter resistors o/c plus cracked print/dry joint's on front pre-amp pcb and scratchy pot's due to wear and tear..not for getting these amps are 30+ years old! built to last and once serviced will last for many more years...
The power stage and be traced out very easy or if you can get hold of the schematic it's plain sailing...a quick tip is ... the cobra power out stage is the same design so can be used to aid repair... such as long tail pair/driver bootstrap cc and the o/p transistors... pre-amp is just a repeat of one channel followed by reverb circuit..
So after replacement of parts and more tidying up this amp was ready for action....
