daseraces13
New Member
hello. got my hands on a 9090 for a pretty good price. when i got it home, it wouldnt come out of protection mode.
im not super knowledged in electronics, but love to learn. tested the main output transistors all tested ok, none were shorted. removed the driver board and the unit came out of protection. so i ordered a driver board rebuild kit. installed everything today, replaced 8 capacitors, 8 transistors, 6 diodes, 2 ziener diodes and all fusible resistors. found 2 resistors that tested at just about 1 mega ohm, basically open. put the board in with a dim bulb tester and it came out of protection. set the dc offset and got both channels to about 1.5-3mv.
then(which is where im certain i messed up), i removed the driver board to remove the fuses easier on the power supply board so i can set proper bias. removed the left channel fuse, reinstalled the driver board and the unit wouldnt come out of protection. hooked it up to the dim bulb tested and yup, some sort of short. tested the output transistors again and all still test good, and unit comes out of protection with driver board removed. assuming i shorted something out when removing the driver board. should have taken this approach in the first place, but now i have to actually find the issue on the board instead of being a parts changer like i thought id get away with(and did until i fried something).
where do i start in this case? there were definitely bad fusible resistors, but (correct me if im wrong) now the resistors shouldnt be the issue. can someone guide me in the right direction? im super bummed about this and hope i can get this monster running good again. thank you in advance for any help!
im not super knowledged in electronics, but love to learn. tested the main output transistors all tested ok, none were shorted. removed the driver board and the unit came out of protection. so i ordered a driver board rebuild kit. installed everything today, replaced 8 capacitors, 8 transistors, 6 diodes, 2 ziener diodes and all fusible resistors. found 2 resistors that tested at just about 1 mega ohm, basically open. put the board in with a dim bulb tester and it came out of protection. set the dc offset and got both channels to about 1.5-3mv.
then(which is where im certain i messed up), i removed the driver board to remove the fuses easier on the power supply board so i can set proper bias. removed the left channel fuse, reinstalled the driver board and the unit wouldnt come out of protection. hooked it up to the dim bulb tested and yup, some sort of short. tested the output transistors again and all still test good, and unit comes out of protection with driver board removed. assuming i shorted something out when removing the driver board. should have taken this approach in the first place, but now i have to actually find the issue on the board instead of being a parts changer like i thought id get away with(and did until i fried something).
where do i start in this case? there were definitely bad fusible resistors, but (correct me if im wrong) now the resistors shouldnt be the issue. can someone guide me in the right direction? im super bummed about this and hope i can get this monster running good again. thank you in advance for any help!
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