Active PA speaker surged and after replacing transisters , it turns on and plays but has distortion

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Sniper19

Member
Joined
Mar 28, 2023
Messages
6
The speaker blew due to an electrical surge.
I replaced the fuse, Replaced all 4 transistors (2x A1941 and 2x C5198) I replaced 2 R100 resisters (brown black brown gold) but still no sound. I also replaced 5W 0.20 ohm resisters. And 63v 3300uf capacitors

I have a Hybrid PB 15" Active Speaker.
Hybrid does not release the speaker schematic to the public.

The speaker comes on and plays but even at a low volume is distorted and sounds blown,
but i've checked the sub and tweeter and thought the capacitor was responsible but i swapped that out as well, speaker continues to play like its blown.

I've been working on it for over a week , replacing parts, the craziest part is that it worked after replacing the transisters , played perfect , than suddenly on a different day
I switched it on and its distorted immediately when turning the volume up , thats when i changed the capacitors but I can't figure out why its happening.
 

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Can you see the distortion on your oscilloscope? If so try to disable the feedback loop and check the signal path (best to use a variac to control the mains voltage as the gain will be very high without feedback). It could be bad contacts in the relays as well usually this will resolve when playing loud.
 
Can you see the distortion on your oscilloscope? If so try to disable the feedback loop and check the signal path (best to use a variac to control the mains voltage as the gain will be very high without feedback). It could be bad contacts in the relays as well usually this will resolve when playing loud.
I dont have a oscilloscope, i only have a digital multimeter, its my personal speakers so investing in the more expensive hardware isn't really the plan as i just have bthe basics , to sort the things i have at home but not really do it as a business , i have the attached multimeter, can i still somehow measure with that?multi.PNG
 
This could be not enough to troubleshoot in this case. Better find someone who has an oscilloscope and some troubleshooting experience. just replacing everything at random can work but is not the way to go.
Please check connectors and potentiometers on the filter/input board.
 
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