Hi all,
i'm in the process of repairing my pg xenon 1200.1. i removed the psu driver board and all the fets. when i install 4 psu fets to test they get extremely hot. with no fets the amp powers up. do i need to install all the psu fets and the driver board to test?
i'm in the process of repairing my pg xenon 1200.1. i removed the psu driver board and all the fets. when i install 4 psu fets to test they get extremely hot. with no fets the amp powers up. do i need to install all the psu fets and the driver board to test?
Do you mean infinite resistance?
Are the gate resistors and any pulldown resistors in the circuit?
Are the gate resistors and any pulldown resistors in the circuit?
If the gate and pulldown resistors are in the circuit and you read infinite resistance, the gate resistors are open.
Does this amp have pulldown resistors on the gate drive circuit?
I assumed it did since it sounded like you were trying to power the amp up without the driver board. If it has no pulldown resistors on the main board and the driver board is out, there is nothing preventing the gates of the PS FETs from charging enough to make them conduct.
I assumed it did since it sounded like you were trying to power the amp up without the driver board. If it has no pulldown resistors on the main board and the driver board is out, there is nothing preventing the gates of the PS FETs from charging enough to make them conduct.
it has no pull down resistors on PS section, i'm still a newbie. would it not power up with the driver board out?
also the source leg is shorted to ground
also the source leg is shorted to ground
It's normal for the source to be connected directly to ground.
Without pulldown resistors, the gates will often charge (they're not much more than a small value capacitor). If the gate charges to more than about 2v, the FETs will begin to pass current and can fail if they overheat.
What's the reason that you have the FETs in and the driver board out? Generally, the FETs are not replaced until the drive circuit has been determined to be in good working order.
Without pulldown resistors, the gates will often charge (they're not much more than a small value capacitor). If the gate charges to more than about 2v, the FETs will begin to pass current and can fail if they overheat.
What's the reason that you have the FETs in and the driver board out? Generally, the FETs are not replaced until the drive circuit has been determined to be in good working order.
I don't have test equipment to check the drive circuit... so i'm trying to figure this out by process of elimination
If you believe that the driver board may be damaged, pull the PS FETs and reinstall the driver board.
Measure the DC voltage across the gate and source (black probe) for all PS FETs. They should all read approximately 5v.
Measure the DC voltage across the gate and source (black probe) for all PS FETs. They should all read approximately 5v.
Hi,
it was easier to replace the driver transistors. I changed below circled, the amp now powers up. now to move onto the output section. Perry how can i test the output driver board before installing fets?
it was easier to replace the driver transistors. I changed below circled, the amp now powers up. now to move onto the output section. Perry how can i test the output driver board before installing fets?
Two notes...
The only two on that board that are PS FET drivers are the two on the top right corner.
If you look at the header pins, you will see copper plating where there shouldn't be any. This indicates that the copper vias were damaged when the board was removed. This can cause intermittent problems which can make the amp unreliable or can be serious enough to cause the PS FETs to fail again. ChipQuik low temp solder can help prevent this.
Did any of the output transistors fail?
Are the two center ICs on the audio driver board coated with potting compound?
The only two on that board that are PS FET drivers are the two on the top right corner.
If you look at the header pins, you will see copper plating where there shouldn't be any. This indicates that the copper vias were damaged when the board was removed. This can cause intermittent problems which can make the amp unreliable or can be serious enough to cause the PS FETs to fail again. ChipQuik low temp solder can help prevent this.
Did any of the output transistors fail?
Are the two center ICs on the audio driver board coated with potting compound?
that image is not my driver, just a random 1 from the net.
below is my driver board
i got this amp with no output transistors, somebody had previously removed them
below is my driver board
i got this amp with no output transistors, somebody had previously removed them
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