A Sound/Video Amplifier With (Protect) On Display Repaired. Model AVR142/230 Harman/Kardon
A man came to my shop and had an amplifier for repair. He said his son put a metal device in the speakers output. After this was done, a (protect) message came on the display every time the amplifier is powered on.
I have seen issues like this before and it is a very easy thing to do but it takes time to take all the parts inside the amplifier dismantled.
Let us begin.
Some screws were off and I could see inside the amplifier. It is an expensive one and it has HDMI output among other impressive features.
It is not a complicated device and as I said before, it takes time to get all the boards out with all these screws mounted on the metal part.
Since the damage as explained by the father was done directly to the output of the speakers, I headed directly to the output transistors and started to check them out. It was not that long time till I came across some shorted components mounted on the heat sink inside this amplifier.
I could not get a wider shot here but I am sure you are getting the idea that I was testing the terminals of the output transistors. Two of these transistors B1559 and D2389 were shorted in all three pins. I also found a fuse resister open on one of its pins.
These were the shorted parts. As for the resistor, it was open only where the arrows are pointing.
All have to do is replacing these two transistors and this resistor and we should be ok.
Here where the two transistors and the resistor located. Since I did not have these exact parts in my shop, I was forced to use different part numbers but did the same function.
These are used parts that were taken from a different amplifier and you will see later on that they did the job well. Take a look
The amplifier was restored and no longer getting the (protect) message any more. I tested it for almost an hour and I was really impressed with the quality of sound and picture that I was getting out of this.
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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Albert van Bemmelen
May 17, 2019 at 6:49 pm
Interesting read about these new amplifiers that have this Protect function integrated. Maybe in future they also make amplifiers that really protect the board output components too before they are destroyed. Now they assumably only protect the speakers from blowing up.
Ram Prakash
May 18, 2019 at 3:23 am
Thanks for the information l really Appreciate.pls tell me what must be the problem in my Yamaha amplifier. Transformer was shorted. Output transistors are OK.changed transformer but led display is not coming.
Ghashaan
May 18, 2019 at 12:31 pm
Another great job done! Enjoyed reading it!
Yogesh Panchal
May 18, 2019 at 9:02 pm
Good job! Waleed
Parasuraman Subramanian
May 20, 2019 at 5:02 pm
Good straightforward job there, because of your expertise! Well done!