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 […]

Read More

Amiga 1200 video DAC information

    Some information about the video DACs If the Amiga rev 1 board uses ( or will be ): ADV101 D215, C215, R215 must be placed on the board. VP101 D215, C215, R215 must be removed from the board. On the lower pins of D233a a 1uF 0805 capacitor must be placed. If you […]

Read More

Amiga – What are those board jump wires ?

Amiga 1200 CCK clock signal – Alice to Budgie The technical reason is that the CCK clock signal coming out of Alice is not clean enough to drive the input on Budgie. It was cheaper for Commodore to clean the signal up using a buffer chip in stead of fixing the Alice chip itself. They […]

Read More

Amiga – memory dram and expansion modules

On this page you’ll find information about memory dram modules and expansion units for Amiga machines. Dram modules used on various amiga machines Amiga 1200 – Rev 1d HM514260JP8 Amiga 1200 – Rev 2B OKI M514800-80J ( datasheet ) Ram Expansion Amiga 600 Ram Expansions https://github.com/SukkoPera/OpenAmiga600RamExpansion   This page is work in progress

Read More

Amiga mainboard frequencies

Frequenties overview Pal system HSync 15.625 KHz VSync 50.00028194 KHz PAL_Hz=Systemclock/227/312.5 28Mhz 28.37516  MHz 14Mhz 14,18758 7Mhz 7.09379 MHz Y451 4.43619 MHz Y621 3 MHz NTSC system HSync 15,750 KHz VSync 59.94005233 KHz NTSC_Hz=Systemclock/227.5/262.5 28Mhz 28.63636 MHz 14Mhz 14,31818 7Mhz 7.15909 MHz Y451 4.43619 MHz Y621 3 MHz  

Read More