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Hi, My C64 boot up with wrong character and with garbage message on the screen. I use Diag Test Cart to diagnose it, it says "NGZERO 0002E02". Because Zero Page memory is internal to the 6510, does it mean 6510 MPU is failed? I tried replaced all 4164 RAM chips, but it didn't change...

I bought a special TRS-80 Model I mainboard in flea market. It's so special, look like integrated with expansion interface. I can't find any information of this board. I think it was made in Japan (since TEC logo on it) like some Japanese version of M1. It was marked as "HE11E016530" and...

Hi, I got a MODEL I (26-1001) recently, but it could not startup. When I push the power button, there is only a scanline on the monitor, just like lost h-sync. First I checked the power output, +5v, +12v and -5v are all normal. I tried to replace Z80 chip and all RAM chips, but it still...

Hi, I have a TRS-80 CC2 which model no is 26-3127. I checked the manual and found that it may simlar to 26-3027. Please check the mainboard: When I power on, the display screen twisted at first: I found +5v of all chips is below 4v, about 3.5v. The AC input is not AC15v, it measured only...

My CBM 4032 can COLD boot to COMMODOR BASIC 4.0 and the cursor flashes normally. But when I press Enter, the cursor is missing and system hang. No response when I pressed any key. If I reset system (toggle power switch) after it runs for a while (2-3 minutes) (HOT boot), the beeper will chrip...