A British guy who owns a local radio station brought his heavy old sound mixer for repair. The moment he stepped into my shop, I could smell the nasty burn mixed with other things that I could not recognize but later on the guy explained with happened (it was a cat pee as the customer explained).

Sound craft is a very good name for sound mixers. During my 12 years experience in sound mixing and TV production with a Canadian company I have used this kind of sound mixers and fell in love with them.

This kind of mixers only designed for radio production because it has some feature built in for such field. Anyway, let the repair begins.

As I took the cover off I could see the inside of this device and as I did that the burning smell was more intense.

First thing that I noticed was the burn on this board. It looked very nasty but I managed to get the board out for close inspection.

That is the cable that connects all the board together and as you can see, it was really burnt but with some cleaning, I realized it was only the plastic that was burned not the actual wiring inside.

This is a closer look to the burnt board and from the look of it and comparing it to the other boards next to this one that only two connections were burnt, the +17 volts rail and the ground rail.

This is the other side of the burnt board and it is burnt but not as bad as the other side.

When I compared this board to the other inside the mixer these were the only connection that I had to make to get it to work.

I took the main connection off board and did some cleaning to it and put it back, cleaned all the soldering joints, and re soldered all the joints that need soldering.

I came across this IC and by looking at its legs I noticed some burn mark there as well.

Please click on the above photo to access the datasheet

It had to be replaced but I could not find the same exact number of it so I replaced it with HCF4053 FB with was exactly the same thing but different letters.

I installed the replacement IC on board and powered up the sound mixer and I could see some LED lights coming on.

The power supply of the sound mixer was on and steady on all voltages. I called the customer and he came and took the mixer. He was happy that the mixer was alive again.

Mission accomplished.

This article was prepared for you by Waleed Rishmawi, one of our ‘Master Authors’ and currently working in the Bethlehem area of Palestine repairing electrical and electronic equipment.

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Note: You can check his previous repair articles in the link below: https://www.electronicsrepairfaq.com/a-dead-hair-straightener-brought-back-to-life-model-philips