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Old 28th June 2020, 03:56 AM   #1
diyAudio Member
Join Date: Jun 2020
Default SWAN M50W sub woofer circuit

I have Swan M50w built in Amplifier with 120 w 8ohms sub woofer

Amplifier by tda7265 is working good with out sub woofer speaker

Sub woofer tda7294 has been replaced but worked only for few months.
Commone external digital volue control with press muting.
When switched on I get hum at Sub woofer and pin 2&6 spark observed and i get 42v at pin 14.
dual power supply rails +/-22v and +/- 32v are okay.

Iam basically Electrical Enigeer and Electronic hobbiyst.
and not doing repair business
tda7294 bootstrap cap-47 microfared 25v and 5 ohms resistor inseries with 104cap is connected between pin 14 & earth
22k resistor between pin2 &14 ,all as traced in the PCB
Kindly Suggest with guidelines to proceed further
I am in need of Circuit diagram with components values

Last edited by BALASUBRAMANIAN; 23rd July 2020 at 04:28 AM. Reason: Hope fully , I could analize and find root cause
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Old 12th July 2020, 07:50 PM   #2
DoofusOfDeath is offline DoofusOfDeath
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Join Date: Jul 2020
My M50W seems to have the same problem.

A month ago, I was using the system in a normal manner. I touched the control puck and got a mild shock, which I assumed was static discharge. The subwoofer immediately made a very loud low-frequency hum for about 5(?) seconds, and then went quiet. There was a faint aroma of cooked electronics.

I opened up the unit, and got a really strong odor of cooked circuits. I visually inspected the PCB and didn't notice any damaged components. However, the primary fuse (3.15 amp) was blown.

I finally got a chance to replace the fuse today. I opted for a fast-blow fuse, just in case the underlying problem was still there. When I powered the system up again, I once again got the low-frequency hum followed by silence. It only took 1-2 seconds to go quiet though, which I assume is thanks to my choice of a fast-blow fuse.

If someone knows where I can get replacement parts at a reasonable price, I may attempt the repair myself.

Otherwise, it's a toss-up between trying to find an affordable repair shop vs. replacing the whole system. I really hate the idea of throwing out 3 perfectly good speakers just because I can't affordably repair one small part of the system.
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