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Mission MS 200 Schematics / Repair pointers (lemmy.world)

submitted 9 months ago by boojumliussnark@lemmy.world to c/askelectronics@discuss.tchncs.de

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I have a Mission MS 200 Subwoofer where the power supply has stopped working. I was quite happy with it, and would like to try to fix it, also I don't have the money for another. I have taken it apart and have narrowed the fault down to the PSU. I have visually inspected the solderings and components, and nothing obvious is wrong. I am not good enough to be able to reverse engineer the board, and was hoping there might be someone here with access to a schematic? Failing that, any pointers on where to maybe do some in-circuit measurements to narrow down which part(s) might be broken, would be very highly appreciated!

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[–] boojumliussnark@lemmy.world 1 points 8 months ago (1 children)

Thanks again for looking at this!

The NTC meassures very low ohm, in circuit it's around 14 ohm.

The markings on the "receiver" board are: +27v, gnd, -27v and "mute".

I would like to try to do some "divide and conquer" debugging, as the total number of components is rather low. I would like to try to eliminate the different "blocks". Like I can connect it up, and measure the voltage after certain "stages". Maybe after the inrush current limiter? To my very limited understanding that should be right at the end of the AC block/stage? Maybe dividing the board into 3 or 4 stages like this I could start to narrow down the issue?

[–] Goodman@discuss.tchncs.de 1 points 8 months ago* (last edited 8 months ago)

You could try that yeah, start at the AC input and work your wayt to the DC output to and find out where the circuit fails. If you want to do that though I'd recommend that you take 2 good pictures of the front and the back, put them side to side and sketch out the circuit diagram. It's no use trying to measure voltage nodes if you don't know what they are supposed to be. Question is if that is worth your time, there is certainly some educational value but there is always a chance that you just won't find the fault.

If you do make a schematic then react to my post. I'll try to help you with reading the circuit if you want.