Hi guys,

How do you remove mosfets heatsink from PSU board to check a diodes? Do I need first to unsolder transformers to unscrew the transistors?
I have no any signs of life in psu board: C40 on amp boards were blown, no relay switching, 0V at CN4-5 outputs. How can I check if D6, D7 are ok? Seems like they are open in both directions.
Update: TOP243 was dead, replaced.
Has anyone managed to power the amp boards directly without control board with aim to use a sub only?

This post has been edited by Andriyol: Jan 30 2021, 08:21 PM

Hello everybody,

I'm new to the forum and i need your help

I will soon finish repairing the S750 of my friend : I cleaned up all the glue and replace the caps as indicated in the forum. when I tested the subwoofer the sound was noisly and low. so I deepened my research on the audio process board and I noticed that there is a SMD component that was cracked (C66). I join you the photos






can someone give me some information about the value of this component ?
if anyone can help me that will be really nice

C66 is a CMD capacitor. I'll be a little free tomorrow night and try to figure out what capacity it has.

Thank you very much in advance. I'm really stuck.

I think that C65 have a same value of C66 and effectivly that's CMD capacitor.

I don't find the schematic of audio process board (the model is MS0490C)

if it helps i tried to follow the leads and made a diagram from this but is very incomplete.

Thanks again....




Attached thumbnail(s)

i forgot to precise the values of C218 and C220 is 100uF 16V

Hi all,

While cleaning the audio processing board, PN: PBMs0490c0420, a surface mount capacitor popped off with the glue. The capacitor is C11 and appears to be connected to component U3 (part 4556a).

Does anyone know the rating for C11? The capacitor is located next to U3, and resistor R29; from my orientation it is the top right of the board. I have a suspicion that capacitance is the same as C13

All,
In case anyone needs to know in the future, C11 and C13 appear to be 100pF 0603 capacitors. MichaelD was kind enough to measure C11 and I removed c13 and measured it as well. The opamp the capacitors are connected to is rated at +/-18 volt for the rails, so a 25V or 50V rating should be sufficient. I've ordered some 100pF, 50V capacitors to replace the one that was lost.

I just want to say thanks to everyone who provided information for these repairs. I just put in the last two capacitors and electronic silicone today and finally have sound again after more than a month.

All 7 speakers are wired up again and I'm using them gently for a few days while the silicone fully cures.

hello everyone,
I come back with my problem, post above, the values of the SMD capacitors (c65 and c66). I could'nt find their references despite a lot of research.

I leave it to the experts of this forum to help me finalize the repair of this magnificent subwoofer.

Thank you very much in advance and I'm counting on your help guys

I am sorry to tell you there is no repair shop, you need to find some willing specialist to fix this in your location, but you must know that the fix for this speakers needs tons of time and tons effort and some money (sometimes a lot of money compared to actual value of the speakers.) No commercial repair shop will take this job because it will cost you more than its original price. Or try it yourself following this topic.

There is a lot of bulged caps, replace all capxon junk and the other lytics as well.

Fot he part 100M 05399, i have no idea what it is.

You can track the red and black paired wires from the amp boards connected to the JST-VH connectors on the I/O board, there are marking on the pcb which channel it is.