I have an old car audio amplifier, PPI PCX2400 class AB switching, and am attempting to repair myself. I have 10 years of industrial controls experience, but never have gotten too much into circuit board troubleshooting. I have printed datasheets on some of the components, MOSFETS, H Bridge, and PWM-SG 3525A.
So far here is what I have determined:
There are 12 RFP70N06 (mosfets) on each channel (2 channels). All 24 (total), were destroyed. I have shorts from the Source to the Drain on all of them. Each side is of MOSFETS appears to be controlled by an HIP4081 High Freq Full Bridge Fet Driver. All the gate resistors seem intact and read 22 Ohms. The output transistors (?) A1303, all seem to be fine there is 70 Kohms between the drain and source, and 56 ohms from source to gate.
There are 2 resistors that were visibly damaged. I can't see the stripping anymore and ohm'd them out but don't know if this is accurate given their condition.
One of the resistors was 10 ohm and was on terminal 15 and 16 of the HIP4081A. This then went to the drain of one of the mosfets. I believe this was switching the positive side?
The other resistor was 3.3 ohm, and was connected between terminal 15 and 16 of the other HIP4081A and was connected to the B- terminal where the power is supplied.
I know I have to replace the MOSFETS, but I'd like to find the source of the problem before I fry $50 in transistors....again.
I know this is a long shot, but any help would be appreciated.
I do not have a schematic, but am going to attempt to make one
So far here is what I have determined:
There are 12 RFP70N06 (mosfets) on each channel (2 channels). All 24 (total), were destroyed. I have shorts from the Source to the Drain on all of them. Each side is of MOSFETS appears to be controlled by an HIP4081 High Freq Full Bridge Fet Driver. All the gate resistors seem intact and read 22 Ohms. The output transistors (?) A1303, all seem to be fine there is 70 Kohms between the drain and source, and 56 ohms from source to gate.
There are 2 resistors that were visibly damaged. I can't see the stripping anymore and ohm'd them out but don't know if this is accurate given their condition.
One of the resistors was 10 ohm and was on terminal 15 and 16 of the HIP4081A. This then went to the drain of one of the mosfets. I believe this was switching the positive side?
The other resistor was 3.3 ohm, and was connected between terminal 15 and 16 of the other HIP4081A and was connected to the B- terminal where the power is supplied.
I know I have to replace the MOSFETS, but I'd like to find the source of the problem before I fry $50 in transistors....again.
I know this is a long shot, but any help would be appreciated.
I do not have a schematic, but am going to attempt to make one
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