Looking for some help. I have a sick MRP-M650. The output FETs were removed to check for shorts and they tested OK. When I measured voltages on PS FETs and driver IC (494), most everything was normal, however I found a shorted MURs120 that I replaced.
I put the last 3 output FETs back into the amp, powered on and tried to measure waveforms only to find the amp seems to go into protect. the only thing I can think of is the driver IC on the opposite channel is shot. When the last 3 FETs were removed, IC307 measured ok but had the shorted diode (MURS120). IC308 showed -21v on pins 6,7 & 8. My questions is, how could putting the FET's back into the board all of a sudden cause all of the other components I measured ok before, to most not showing voltage? Did I answer my own question?
If it helps, when the last 3 output FETs were removed, I got a nice clean square wave on all 4 PS FET's, the dual diodes measured ok, the 494 measured ok but when I put those last 3 FETs in everything went haywire. Oh and before you ask, I put all new IRF540N's sourced from MOUSER.com
I put the last 3 output FETs back into the amp, powered on and tried to measure waveforms only to find the amp seems to go into protect. the only thing I can think of is the driver IC on the opposite channel is shot. When the last 3 FETs were removed, IC307 measured ok but had the shorted diode (MURS120). IC308 showed -21v on pins 6,7 & 8. My questions is, how could putting the FET's back into the board all of a sudden cause all of the other components I measured ok before, to most not showing voltage? Did I answer my own question?
If it helps, when the last 3 output FETs were removed, I got a nice clean square wave on all 4 PS FET's, the dual diodes measured ok, the 494 measured ok but when I put those last 3 FETs in everything went haywire. Oh and before you ask, I put all new IRF540N's sourced from MOUSER.com
If you cannot find the fault, send me the service manual and I'll try to help.
babin_perry@yahoo.com
babin_perry@yahoo.com
Hi TiminMi, I have the exact same app while I don’t my cousin dies and hers is acting up I was wondering if there’s anyway possible you could help me out with the service manual as you have said you do Have it, could you please if you can let me know if you can help me out I would like to get this thing working again for her vehicle
Last edited:
