LG home theater model HT806 came in dead now repaired

 I got a phone call from one of my neighbor who wanted his home theater checked by a technician.

I passed by his place and took the machine to the shop, he has given me a hint that he suspects the machine was hit by power surge.

Once in the shop I applied power and indeed the machine was dead as dodo.

I decided to open the machine and straight to the safety components and found all of them were intact.

Checked for any capacitor with the top silvery part swollen and everything looked good as you can see below.

I did voltage testing and almost all voltages were present though I noted one line which was rated 6.4 volts was 10 volts.

I tested the standby voltage and was present up to the remote receiver at 3.5 volts.

Usually if this voltage is present at least I expect the power ON Led to be light but in this case the machine just appeared dead.

I decided to un-bolt the power board and scan the bottom side and this is what I saw.

Everything again looked okay though I noted a small area with some burnt mark(dark).

Across the two black spots was a diode labelled D953.

I decided to test this diode and to my surprise I got beep from my meter.

I decided to lift one leg of the diode out of the circuit and re tested again and still I got a beep.

This confirmed that the diode is dead short and needed replacement even before going on with the troubleshooting.

In electronic troubleshooting we begin with known to un known.

The diode was FR (fast recovery) diode and therefore needed to be replaced with the same FR diode.

I got one from my kit and after replacement I applied the power, with my eyes on the panel and was welcomed with these words…HELLO.

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