Need help to repair JBL ES150 Subwoofer Amp

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akraj

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Joined 2010
Hello:

I would be grateful if you can help me to repair my JBL ES150 Subwoofer. Few days ago I found that there is no power light and with my little knowledge of electronics I attempted to repair that. After opening I saw that the main fuse and output FETs are toasted!

I replaced the FETs and fuse. Power light came back but orange! Further checked and found that the (DC) +V is coming to speaker line and relay is not engaging to save the speaker.

I have measured voltages of some areas and all of the places, +V is present with respect to GND. Now would you please let me know what and how I can check to make the sub live again!

In the picture red marked points are +V. FETs are okay.
 

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akraj

Member
Joined 2010
JonSnell Electronic said:
Make sure the op amp is running with a nice square wave output on pin 1. Check the driver transistors, 2k2 resistors and turn off diodes first
Click to expand...

Thanks a lot for your time to rely. I checked driver transistors and they are fine in digital meter. I will check op amp and will post updates.

Thanks once again.

:....2k2 resistors and turn off diodes" - can you please let me know a bit detail
 
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akraj

Member
Joined 2010
akraj said:
Thanks MANOJ, I removed the power transistors but not Q1. without power FETs V+ is present at speaker line. I will check osc at C3

Thanks once again.
Click to expand...
I was busy with some other issues and have got the time to check.

Yesterday I found that the 12V zener diodes (Z4, Z5 and Z6) shorted. Driver transistors are toasted. OP amp voltage was 17V (Pin 4 & 8) when I removed that it is 24V now. Seems that the OP amp also gone. :(

It's really difficult to find SMD part in my local market. However, trying to arrange them. Will keep you posted.
 
Eva

Eva

Member
Joined 2003
Z5 and Z6 blown imply almost all output stage is blown.
Z4 blown is different issue, in the sense that, by looking at the schematic, I can't find any chain reaction that can lead to Z4 blown, unless Z4 was the one that blew first, resulting in wrong drive of output stage and all blowing.
 
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akraj

Member
Joined 2010
Eva said:
Z5 and Z6 blown imply almost all output stage is blown.
Z4 blown is different issue, in the sense that, by looking at the schematic, I can't find any chain reaction that can lead to Z4 blown, unless Z4 was the one that blew first, resulting in wrong drive of output stage and all blowing.
Click to expand...


I replaced output FETs first and later on found than other components were fried as well.

However, I ordered the full amp module and waiting for delivery to Bangladesh.

I will try to rebuild the board until ordered one arrives. Thanks Eva for your reply
 
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