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SPL Dynamics S-4002 - Output shorted and power half dead
SPL Dynamics S-4002 - Output shorted and power half dead
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Old 2nd June 2012, 06:48 PM   #1
mns80 is offline mns80  Finland
diyAudio Member
Join Date: Sep 2010
Default SPL Dynamics S-4002 - Output shorted and power half dead


This is the second time I have the amplifier open and messing around with it.

First time was for fun, wanted to know if I were able to get it working. As the owner, a friend of mine, said that he tested with a very weak battery and nothing happened I applied some power to it to test if anything happened. This resulted in a cracked FET in the power section and a small fire. Some measurements later, one output transistor and the blown fet. Ordered some new parts soldered in and applied some power again. No smoke nothing but DC on the output. More measurements and the conclusion was a shorted Zener in the regulator for the preamp section. replaced it and Amp was working fine with sound and all. Installed in car to test with some more power and it worked fine one and a half day. Everyone was happy until it suddenly was silent again.

No is the second time I have it open. Same bank output transistors shorted, however I did not apply any power this time to blow something up. After some desoldering I applied power to see if power supply was in order, nonono, one toroid is not giving voltage, same side as the output and same as where the fet blew last time. All four fets in the power section look kind of strange on the back, like the metal has almost melted in one spot. These are FQP50N06.

Can anyone suggest what to do with this amp, will it again work one and a half day again if I replace the same parts or is there something else I should consider too?

Please note that I am sort of a noob with amp repair.

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Old 4th June 2012, 03:07 AM   #2
Perry Babin is offline Perry Babin  United States
diyAudio Member
Join Date: Nov 2003
Location: Louisiana
All power supply FETs in the failed supply have to be replaced at once. You must confirm that all gate resistors are within tolerance. You also have to confirm that you have a good drive signal. If the gate signal isn't as is should be, you need to check the driver transistors.

Post a photo of the board in the amp if you can't repair it so we can see what you have.
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