While using a converted ATX PSU (or an ATX PSU with an adapter) only 1MB Fast RAM is detected per bank, so 16MB RAM shows as 4MB total, all other functionality is working on the board: Cause: _FAIL (Pin1 – Grey) on the A4000 motherboard power connector is not wired up correctly to the ATX PWR_GOOD […]
Category: Commodore
Working Amiga 4000 motherboard freeze then green screen after few minutes
Amiga 4000 motherboard works from cold boot, then freezes after few minutes and shows green screen after reset. Cold boot (after about 5 minutes) would restore the board, then symptoms repeat. No corrosion in the battery area. Solution: U212 controlling CAS/RAS is unusually hot, inputs are OK, but outputs show undefined “half” (pulling low from […]
A4000 internal FDD does not work when external FDD is connected
When an A4000D Rev B have an external drive connected the internal drive stops working. Tries to boot on startup, but gives up after 3 times trying to read the disk. When the external drive is disconnected the internal FDD works as expected including boot. Also if the internal drive disconnected (by cable) the external […]
A4000 Rev B stuck at early boot (grey screen)
Newly built A4000 motherboard. Tested all resets, supply voltages, and there was video out. DiagROMs would also not initialize, indicating very early fault during boot (during reset routine). _OVL signal on CIA B (U350) would go to high at hw. reset, but would not return to low indicating the CPU didn’t write back to CIA […]
HDD Led always bright using some SD/CF Adapters
Some SD/CF Adapters makes the HDD led always bright and you can see a flight flicker when the disk is loading. This can easy be fixed by replacing the PNP Transistor Q631 with a PNP Transistor with an extra Resistor just like the PDTA123ET Transistor. now HDD light will behave normal.