By MisterWhite
Fri Mar 23, 2012 9:59 pm
One of my customers fitted a backlight into his MPC3000, and found that the backlight would not light. Just so I could double check the wiring in his machine, he sent me a photo. And this is where things get a bit strange.
The backlight's inverter on the MPC3000 gets its 5VDC power directly from J6 on the CPU PCB. A pair of cables, 5V and GND, should run from that J6 to W851 on the filter PCB, to supply power when the backlight is switched on.
On this 3000 though, one wire has been removed from the J6 connector and soldered to another board. The red wire from that pair is now soldered to what seems like the underside of the Footswitch board. At the filter PCB end, both cables go into the correct place, into W851.
Sorry for the crappy pic. If you look at the inverter on the filter PCB (top centre), above that there's a pair of wires (red + white) that should run down towards the CPU PCB into J6. But here, the red wire splits away from the pair and is soldered to, we think, the footswitch board.
I can't work out what this mod was meant to acheive, but it's certainly going to stop the inverter/backlight from working. I seem to remember reading about a mod to rectify some noise, due to the Akai circuit design using the wrong ground (analog vs digital) somewhere, but I just can't find it.
Can anyone point me in the right direction as to what this was supposed to do?
Cheers,
Matt
The backlight's inverter on the MPC3000 gets its 5VDC power directly from J6 on the CPU PCB. A pair of cables, 5V and GND, should run from that J6 to W851 on the filter PCB, to supply power when the backlight is switched on.
On this 3000 though, one wire has been removed from the J6 connector and soldered to another board. The red wire from that pair is now soldered to what seems like the underside of the Footswitch board. At the filter PCB end, both cables go into the correct place, into W851.
Sorry for the crappy pic. If you look at the inverter on the filter PCB (top centre), above that there's a pair of wires (red + white) that should run down towards the CPU PCB into J6. But here, the red wire splits away from the pair and is soldered to, we think, the footswitch board.
I can't work out what this mod was meant to acheive, but it's certainly going to stop the inverter/backlight from working. I seem to remember reading about a mod to rectify some noise, due to the Akai circuit design using the wrong ground (analog vs digital) somewhere, but I just can't find it.
Can anyone point me in the right direction as to what this was supposed to do?
Cheers,
Matt
Plug + play backlights and displays
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