Hi,
I got this amplifier and i am struggling for few days now to repair it...
Let's start with beginning: When i firs got it i found out that power supply is shorted and i measured power supply FET's , 11 out of 16 dead, so removed all of them . (There are 2 transformers on the power supply side, 2 banks for each transformer).
I then measured the square wave on all banks, all good like in attached pictures.
I then moved to the amplifier section, found out few dead FET's, removed all of them , then placed one FET on each bank from the power supply and powered up... Rail voltage climbed up for both rails, but.... too much current was drawn from the power supply ( > 8 Amps) and 2 of the power supply FET's heating up very quickly...
Next step was to remove rectifiers just to isolate the power supply, same problem...
I then changed FET's between sides, problem din't move with the FET's, it's on the same side.
I measured transformers coils with a cheap component tester, they are showing about the same value of inductance ...
I attached pictures with the square wave without FET's for both sides and Square wave with FET's attached for both sides.
I will refer to A as the good side and B as the bad side. It's visible that the square wave on the B side is wrong after FET's are attached, while looks OK with FEt's removed.
Do you have any idea? Can be the driving IC? Or the buffer transistors which may be fine with no load, but may go crazy when they actually need to drive the FET's?
i need also to mention that the side which is heating the FET's had more damage than the other one.
Any suggestion are welcome....
thanks in advance for helping!
I got this amplifier and i am struggling for few days now to repair it...
Let's start with beginning: When i firs got it i found out that power supply is shorted and i measured power supply FET's , 11 out of 16 dead, so removed all of them . (There are 2 transformers on the power supply side, 2 banks for each transformer).
I then measured the square wave on all banks, all good like in attached pictures.
I then moved to the amplifier section, found out few dead FET's, removed all of them , then placed one FET on each bank from the power supply and powered up... Rail voltage climbed up for both rails, but.... too much current was drawn from the power supply ( > 8 Amps) and 2 of the power supply FET's heating up very quickly...
Next step was to remove rectifiers just to isolate the power supply, same problem...
I then changed FET's between sides, problem din't move with the FET's, it's on the same side.
I measured transformers coils with a cheap component tester, they are showing about the same value of inductance ...
I attached pictures with the square wave without FET's for both sides and Square wave with FET's attached for both sides.
I will refer to A as the good side and B as the bad side. It's visible that the square wave on the B side is wrong after FET's are attached, while looks OK with FEt's removed.
Do you have any idea? Can be the driving IC? Or the buffer transistors which may be fine with no load, but may go crazy when they actually need to drive the FET's?
i need also to mention that the side which is heating the FET's had more damage than the other one.
Any suggestion are welcome....
thanks in advance for helping!