Yamaha DXR12 Powered Speaker Protection Light On

[JBTanks]

I got a Yamaha DXR12 speaker that the portection light was staying on and found 2 of the 4 mosfets (3603) bad on the Amp board. Replaced all 4 mosfets and this is my problem now and would appreciate any direction to help correct my problem. After replacing mosfets the speaker would power up and work fine, however if I turn it off and try to turn it back on the protection light would stay on and speaker doesn't work. Now if I leave the speaker off for 30 minutes and turn the speaker back on it would power up and work again. I was timing this cycle when it would start working again and 5, 10, 15, and 20 minutes wasn't long enough but at 30 minutes it would work again.

 

[Nigel Goodwin]

For a start check is there is any DC on the outputs of the amplifiers?, if not check the over current protection circuits - these monitor the voltage drop across low value resistors, which could have been damaged by the transistor failures.

According to the manual there are two amplifiers - so why did you replace transistors in the one that wasn't faulty?.

 

[JBTanks]

Should there be no dc at all or is there an amount that it shouldn't be above. I replaced four fets of same value because I removed all four to check and didn't want to put back the ok ones since I removed them. Thanks for your reply and will check the dc and current protection.

 

[Nigel Goodwin]

Should there be no dc at all or is there an amount that it shouldn't be above. I replaced four fets of same value because I removed all four to check and didn't want to put back the ok ones since I removed them. Thanks for your reply and will check the dc and current protection.

There should be zero volts, or very close to it - certainly well under 1v.