A few days ago I got a knock at my gate very early in the morning and I wondered what could have necessitated the visit and I almost came out armed.
Upon opening the gate I found one of my neighbor standing there holding a woofer and after excusing himself he told me that he wanted it checked urgently and he suspect it burnt after the power surge though I can’t remember experiencing any in my house.
I took the machine and kept it in my workshop which is within my house and went to work. In the evening I came back and went straight to the woofer and before opening I could smell something burnt inside and after opening this is what I saw.
Yes! The four bridge diodes were burnt beyond recognition.
Before continuing I decided to check if the transformer was gone or not and after dis-connecting it from the board I applied the power and I was able to test all the outputs and were okay and with this I concluded the transformer was okay.
To me this was a big relief since getting the spare for this kind of transformer is not easy in my place.
I decided to replace the four diodes and therefore I removed them carefully and replaced them, since the two fuses were okay I did not suspect any more components shorted.
I then decided to apply the power with the motherboard connected but since I was not sure if there were any other component shorted I decided to use my series lamp current limiter.
After applying the power I noted the bulb remained bright and this means there was still something shorted in the system.
To get the culprit I decided to use the touch method whereby after applying the power via the series bulb for a few minutes dis-connected the power and started touching main suspect component which are prone to shorting like transistors, I.Cs and I after touching one of the amplifier I.C TDA2030A I noted it was very hot for my finger and concluded this must be one of the culprit.
Also keen observation I noted one of its leg was dark meaning it was getting very hot to the point of changing the color as you can see the picture above.
I pulled it out of the circuit and again applied the power and this time the series bulb lite and then went off.
This is a good sign that no more shorted component in there and therefore got a replacement ic TDA2030A which was readily available in my store.
I replaced it and after applying the power I got aloud humming sound from the woofer and I concluded I may have finally got the system working again.
Here is the inside of the woofer
Thank you guys
See you in the next class