I got the wires back to front on the upper VUK (earthquake) coil.
This blew F5. I realised what I’d done and corrected it.
Bear in mind I don’t have a dmd currently so can’t see any messages.
1. I fired the machine up and pulled out the upper coin door switch in order to get a test game to play. Everything was perfect until the ball went in the upper VUK and F8 blew.
2. I checked the PPB and everything seemed fine - diodes and transistors all flow/block as they should and give virtually identical readings. Then checked the CPU (on bench) and got the same - all readings almost identical. Also did continuity tests to Gnd on the board, from the transistor tabs, AOK. The same when refitted to the back box.
3. Then checked the diode on the VUK coil and it was blown.
4. Having replaced the diode, I fired the machine up and pulled out the coin door switch - the VUK plunger just sticks up out of the play field (giving me the finger). So I push the coin door switch back in, it drops, and then with coin door closed, if i press either flipper button, it just raises and lowers (slowly) with each press!
I thought I had it sussed with the diode on the coil, although was fully expecting to replace Q42/Q4 but again they test just fine as far as I can tell.
I was gonna just start replacing all the transistors on the 50v section of the CPU and all the diodes on the 50v coils but that felt unnecessary given the tests and creates scope for more problems so I thought I’d ask you guys your opinions first.
Should I just start replacing transistors even if they test OK, or start looking upstream?
Is there a way to test the signal from the IC to the smaller transistor with the game on and F8 removed?
@Moonraker has already been a star and pinged me a few tips.
This blew F5. I realised what I’d done and corrected it.
Bear in mind I don’t have a dmd currently so can’t see any messages.
1. I fired the machine up and pulled out the upper coin door switch in order to get a test game to play. Everything was perfect until the ball went in the upper VUK and F8 blew.
2. I checked the PPB and everything seemed fine - diodes and transistors all flow/block as they should and give virtually identical readings. Then checked the CPU (on bench) and got the same - all readings almost identical. Also did continuity tests to Gnd on the board, from the transistor tabs, AOK. The same when refitted to the back box.
3. Then checked the diode on the VUK coil and it was blown.
4. Having replaced the diode, I fired the machine up and pulled out the coin door switch - the VUK plunger just sticks up out of the play field (giving me the finger). So I push the coin door switch back in, it drops, and then with coin door closed, if i press either flipper button, it just raises and lowers (slowly) with each press!
I thought I had it sussed with the diode on the coil, although was fully expecting to replace Q42/Q4 but again they test just fine as far as I can tell.
I was gonna just start replacing all the transistors on the 50v section of the CPU and all the diodes on the 50v coils but that felt unnecessary given the tests and creates scope for more problems so I thought I’d ask you guys your opinions first.
Should I just start replacing transistors even if they test OK, or start looking upstream?
Is there a way to test the signal from the IC to the smaller transistor with the game on and F8 removed?
@Moonraker has already been a star and pinged me a few tips.