progress! the problem seams to lie in this area, the little cathode (is it?) in the middle isn't putting any power out which in turn feeds the little transistor on the left which in turn powers pin 15 on the pwm. i have sourced another part but not sore if there any specific values to these things or not (amature!). it's quite funny as where this project started was right here with the burnt toroid and it probly took the transister and cathode out with it at the same time! any thoughts??
An externally hosted image should be here but it was not working when we last tested it.
If the transistor's center leg goes to pin 15, the left-most leg (looking at the side of the transistor where the numbers are written) should have +B. The power likely was connected to the burned area. Clean the area well on both sides of the board and see if you can find the trace.
hmm, interesting! looking at the front on the transistor like you said the trace seams ok but it's not showing 12v! when i take the toroid out it shows 11.xx volts and the main fuses read 14.xx volts!! put the toroid back in and there's no voltage what so ever at the left leg.😕
i will resolder the trace as it's only short anyway, maybe it's a dry joint now.
i will resolder the trace as it's only short anyway, maybe it's a dry joint now.
good news!! resoldered that trace and we now have power! all 4 led's on the board are lit up and the power on led is on. all i have to do is build it back up and see if i have any sound 🙄
looks promising though.
looks promising though.
was good news🙁 i left the amp on too long with it out of the heatsink and now one of the toshiba transistors has toasted itself! still, should be an easy fix and next time i'll build the amp back up before i turn it on!!
just myself a brand new ms2250 with shrowd too, so things are looking good!!
just myself a brand new ms2250 with shrowd too, so things are looking good!!
the amp is now working after replacing the toshiba transistor, i bench tested it for a while yesterday and it never got warm or anything really! although i only tried a pair of mids on it.
thanks to everyone who's helped me with this project, it's been well worth it and i've gained some valuable knowledge on how amplifiers tic!
next project is a smaller ms275 with distortion on one channel😉
thanks to everyone who's helped me with this project, it's been well worth it and i've gained some valuable knowledge on how amplifiers tic!
next project is a smaller ms275 with distortion on one channel😉
Perry Babin said:
Perry, I just wanted to comment on the excellent help you gave Marko during this amp repair.
I know he appreciated it, and I appreciated reading it. Good job!
- Status
- Not open for further replies.