rogue rb120.....musician's friend amp

[acorkos]

this amp was purchased from MF. no schematic or parts list available, or so they told me...when i inquired, they actually sent me a link to the amp on their website...i guess their solution would be to spend $199 for a new one. anyways, one output transistor is shorted, and there are a couple of burned up resistors. r69 and r81....i don't know their values to swap in replacements. any ideas? anyone out there with one of these amps who can tell me the original resistor values?

thanks

[Enzo]

Generally in these cases we make educated guesses. Power transistors can be substituted liberally - very uncritical. In the case of burnt resistors, we look at similar circuits. often teh symmetry of the positive and negative sides gives a clue. If teh positive side driver has a 47 ohm emitter resistor, then chances aer teh burnt up negative side one will also be 47 ohms.

The circuits on these entry level amps are utterly basic, so draw a generic SS power amp curcuit and it will be close. COnsider a value resistor and see if it makes sense on your test schematic.