New 240p method for PAL 3DO

Earlier this year I decided to remove the PAL 3DO video encoder (BT9103) and attempt to replace it with a pin equivalent RGB capable video encoder (BT856).



After successfully removing the DAC, I noticed a trace leading away on the motherboard. I traced this to pin 196 on the CLIO. This meant that the CLIO could change the scan mode of the DAC between 480i and 240p provided the game had an instruction in its coding. This is confirmed in the FZ-1 PAL service manual. The DAC is also set to Master mode according to the datasheet which means that Hsync and Vsync are fed back to the CLIO possibly to provide some sort of timing function. This could explain why some games behave weirdly when we force the DAC into progressive mode.

The service manual shows that PAL 3DO have a resistor (R166) bridging the Interlace signal between CLIO and BT9103. By removing that resistor and soldering a wire to the empty pad on R164, the Interlace pin can be tied high or low without needing to lift the pin on the DAC.



(The wires are left over from the previous 240p mod)







I find this method neater than lifting IC pins and risking damage to the board. Remember if it is a Canadian model with BT9103, R164 will need to be removed instead of R166.

The same method can probably be applied to the VP536 but I don't have a VP536 3DO to test.

The other wires are part of a DAC transplant RGB mod using an RGB capable encoder. Write up to follow soon...

 

Nice!

 

this is doable for the jap one too? i want to put that chip onmine for getting rgb