Hi all,
I have recently been working on a Duo that has had a lot of issues, most of which have been resolved but I am now having an issue where the console boots to a BIOS screen but always says "Press Run Button" as if the door is closed, even when the case is not on top of the console. I have seen some other threads where people have suggested testing the traces underneath the HuCard slot - I have done this and found no broken traces, I have also beeped out all traces to the ICs controlling the disc drive and have not found an issue there either
I feel like I'm finally getting to the end of the repairs for this console, but I am completely stuck as to where to go from here, I have beeped out the entire CD drive circuit using the publicly available schematics and KiCAD with the repro PCB designs on Github and have not found any more broken traces in the circuit
For those who have had this issue before, are there any specific traces that may be relating to this issue I can check and potentially replace as they might be beeping out but have damage on the line that could be causing it to read incorrectly?
Adding diagnostic information:
From what I can see there are several address lines that go through a buffer/driver at IC517 to the large custom chip that controls the disc drive. A8 through to A15 become XA8 through to XA15. Connections for these are where the through hole pins are for the cartridge slot
IC501 - Custom CD controller ASIC D91317GD
IC517 - LS244 buffer/driver
IC515 - Flash memory holding Super CD BIOS (same pins are also connected on IC514 and IC513 - same pins unless otherwise noted)
IC906 - HM6264 SRAM
IC517 - Outputs
Pin 3 -> Pin 10 IC501 -> Pin 28 IC515
Pin 5 -> Pin 16 IC501 -> Pin 26 IC515
Pin 7 -> Pin 13 IC501 -> Pin 23 IC515
Pin 9 -> Pin 8 IC501 -> Pin 3 IC515 -> Pin 31 IC513 IC514
Pin 12 -> Pin 11 IC501 -> Pin 4 IC515
Pin 14 -> Pin 12 IC501 -> Pin 25 IC515
Pin 16 -> Pin 17 IC501 -> Pin 27 IC515
Pin 18 -> Pin 9 IC501 -> Pin 29 IC515
Inputs
Pin 2 -> Pin 70 CPU
Pin 4 -> Pin 78 CPU -> Pin 25 IC906
Pin 6 -> Pin 73 CPU -> Pin 23 IC906
Pin 8 -> Pin 72 CPU -> Pin 2 IC906
Pin 11 -> Pin 69 CPU
Pin 13 -> Pin 74 CPU -> Pin 21 IC906
Pin 15 -> Pin 77 CPU -> Pin 24 IC906
Pin 17 -> Pin 71 CPU
IC518 - Outputs
Pin 14 -> Pin 31 IC515 -> Pin 5 IC501
Pin 16 -> Pin 30 IC515 -> Pin 6 IC501
Pin 18 -> Pin 2 IC515 -> Pin 7 IC501
Inputs
Pin 2 -> Pin 68 CPU
Pin 4 -> Pin 67 CPU
Pin 6 -> Pin 66 CPU
Data lines go through a similar buffer at IC520 and D0 through D8 generate XD0 through XD8 - Outputs do not go under the cart slot and were not tested at this time
Inputs
Pin 2 -> Pin 19 IC906 -> Pin 13 6270 -> Pin 56 6280 -> Pin 5 6260
Pin 3 -> Pin 18 IC906 -> Pin 14 6270 -> Pin 55 6280 -> Pin 6 6260
Pin 4 -> Pin 17 IC906 -> Pin 15 6270 -> Pin 54 6280 -> Pin 7 6260
Pin 5 -> Pin 16 IC906 -> Pin 16 6270 -> Pin 53 6280 -> Pin 8 6260
Pin 6 -> Pin 15 IC906 -> Pin 17 6270 -> Pin 52 6280 -> Pin 9 6260
Pin 7 -> Pin 13 IC906 -> Pin 19 6270 -> Pin 51 6280 -> Pin 10 6260
Pin 8 -> Pin 12 IC906 -> Pin 20 6270 -> Pin 50 6280 -> Pin 11 6260
Pin 9 -> Pin 11 IC906 -> Pin 21 6270 -> Pin 49 6280 -> Pin 12 6260
/WR and /RD lines
These both run under the cartridge slot
/RD
IC515 Pin 24 -> Pin 4 IC519 -> Pin 22 IC906 -> Pin 3 6270 -> Pin 78 6260 -> Pin 62 6280
/WR
IC519 Pin 1 -> IC906 Pin 27 -> Pin 2 6270 -> Pin 77 6260 -> Pin 63 6280
Topic: SOLVED PC Engine DUO - Push Run Button with door open/No LED/No Laser/Disc Spin (Read 452 times)