Leaderboard

Hello everyone. I'm back for a short month. Maybe enough time to repair my second MPU3, if anyone would be willing to help. It won't start. I've replaced the capacitors around the regulator. The 104 capacitors on the MPU, the RAM (NOS), and the transistors in the reset area. (By the way, I don't know where T62 is on the schematic.) So, here are my readings based on what I've read about the MPU3 and my recent experience getting help from Midibob. IC24 74LS03, yes, new. IC10 Pin 3 - 561 Hz square wave. IC18 Pin 12 - 100 Hz R83-84-85-D43-C39 100 Hz R68 and R69 OK C32 and C34 OK IC24 Pin 8: I can't find 2 Hz; nothing. IC9 Pins 10 to 15: only high levels (logic probe). All components in this area have been tested or replaced if suspected. D44 and D45 are also new. No corrosion on the RAM sockets or underneath. Cartridge port is also free. Ah yes, the 5V is at 5.2V. The circled area contains all components that have been tested or are new. So, if you have any ideas where to look, I'm all ears. And whatever happens, we won't throw ourselves into the Thames. :)) Thanks in advance.

OK, the first thing is this is probably a MOD 2 board being as it has a 74LS03 as IC24. The output is now on pin 11. Does it come out of RESET? On switch on it should stay LOW for about 1 second then go HIGH. Do you have the correct RAM fitted, it takes the smaller RAM (in Bytes) 256x4. HM6561 or equivalent. Because of this it won't run later games. T62 doesn't appear in this revision of the board as it has a thyristor (T56) in the RESET circuit.