retroarcademan
n00b
- Joined
- Feb 20, 2020
- Posts
- 7
The title kinda says it all but here's some more background.
Problem:
I have a bunch of NeoGeo CDs in for repair and all but one of them has been repaired. One of them is causing me some issues (I'll call it Unit A).
I thought UnitA just needed a new laser assembly as it wouldn't read CDs, but when the new one arrived the disc still wouldn't spin.
Note that all the motors appear to work. When the lid button is pressed, the laser moves up and down to focus as it should. If the laser is set to the middle of the CD, when the lid button is pressed, the mechanism moves to the inside of the disc as it should.
Fault finding:
- Visual inspection: On inspection I noticed that the lens wasn't omitting the usual red light beam when attempting to focus.
- swapping parts: I swapped this laser from unit A with a working laser from unit B.
The laser from unit A DOES work in unit B (CD spins, game loads flawlessly).
The laser from unit B DOESNT work in unit A.
So I know the laser is not at fault here.
My next step was to swap the laser controller PCB - the one that sits next to the laser and drive mechanism in the top half of the NGCD shell. When I did so, suddenly the fault swapped from Unit A to Unit B.
It seems there is a fault with the laser control board or the associated wiring harnesses.
- Testing:
A quick continuity check tells me the harnesses are fine, so it is indeed the board.
Knowing that FocusGain adjustment can increase laser power I measured the resistance across the FG pot in UnitA and compared it to the same pot in Unit B although I forgot the exact readings they seemed reasonably similar. I'll check later and post them here.
Could this just be a case of a lack of supply to the laser diode? My knowledge of CD player electronics is minimal.
So this is where I'm stuck. I can't find anybody online with a similar problem, and so I can't find a solution either.
Can anybody here help point me in the right direction?
Problem:
I have a bunch of NeoGeo CDs in for repair and all but one of them has been repaired. One of them is causing me some issues (I'll call it Unit A).
I thought UnitA just needed a new laser assembly as it wouldn't read CDs, but when the new one arrived the disc still wouldn't spin.
Note that all the motors appear to work. When the lid button is pressed, the laser moves up and down to focus as it should. If the laser is set to the middle of the CD, when the lid button is pressed, the mechanism moves to the inside of the disc as it should.
Fault finding:
- Visual inspection: On inspection I noticed that the lens wasn't omitting the usual red light beam when attempting to focus.
- swapping parts: I swapped this laser from unit A with a working laser from unit B.
The laser from unit A DOES work in unit B (CD spins, game loads flawlessly).
The laser from unit B DOESNT work in unit A.
So I know the laser is not at fault here.
My next step was to swap the laser controller PCB - the one that sits next to the laser and drive mechanism in the top half of the NGCD shell. When I did so, suddenly the fault swapped from Unit A to Unit B.
It seems there is a fault with the laser control board or the associated wiring harnesses.
- Testing:
A quick continuity check tells me the harnesses are fine, so it is indeed the board.
Knowing that FocusGain adjustment can increase laser power I measured the resistance across the FG pot in UnitA and compared it to the same pot in Unit B although I forgot the exact readings they seemed reasonably similar. I'll check later and post them here.
Could this just be a case of a lack of supply to the laser diode? My knowledge of CD player electronics is minimal.
So this is where I'm stuck. I can't find anybody online with a similar problem, and so I can't find a solution either.
Can anybody here help point me in the right direction?
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