Power Up Basics (PC Engine Duo)
The PC Engine Duo-R has a DC 10V (6.3mm x 3.0mm) center positive power supply.
To power from the bench simply solder wires to the ports rear pins and apply 10V. I would recommend however applying 7V.
The regulators are both just 7805's so anything from about 6.5V to 12V is a fine input. The lower the voltage the less wasted heat, so 7V is ideal.
In completely common sense, the 2 pin harness joining the power board to the motherboard has the red wire is ground, and brown is positive!
Here is the bench red (6-12V) and black (ground) wires attached.
The DC jack passes the positive and ground through a filter, then through the red/brown wire, so check you have continuity from the ground of the DC jack to the red of the motherboard wire, and the positive of the DC jack to the brown wire.
If not, check your inductor filter on the power board has continuity. If not bridge over for now between the sides of the filter. If that is ok, check your 2 pin red/brown wire is ok.
After this ground is system ground, and the power in goes through a reverse polarity protection diode, through the fuse, through the power switch, then into the 7805 regulators input.
You could just grip on the diode and power switch ground for powering from bench without having to solder wires.
The expected power draw when turned on without the CD drive spinning is around 500mA. When the disc spins it goes up to 700mA.
Usually a well tuned disc only pulls 700mA, and one that is struggling to read/seek pulls up to 1.2A.
A successful boot with no HuCard and no disc should yield the Super CD-ROM² splash screen, with Push Run Button! flashing.
If you get a white screen and a HuCard is inserted, it is a failed load of the card. If there is no card inserted, the console thinks there is, so clean the port with IPA.
It can also be an indication of a fault on one of the HU ASIC chips or damaged traces, causing it to fail to boot into the BIOS.
This usually indicates a faulty 6280 or 6270 IC. It can also be traces to them are damaged, or shorts.
If you get this message after inserting a disc and pressing Run then the disc spins and stops with the message Please Set Disc it is a failed disc read so try tuning the laser.