Leaderboard

A bit of a jolly Jackpot tune 20191005_145129.mp4

You might never see one for sale again ? - they are like buses, another one listed this morning (and it is a different one) here

key to maygay is test the RAM pins with a logic probe while there is no card in. They should all be floating (not HI or LO) . If any are showing a signal theres a shorted IC on the databus. Second key is a magic number - 20C0. In nearly al M1 games the very first instruction in ROM ( at 2800h) loads a register with 1. The next instruction after that writes the value in the register to location 20C0. That happens to be pin 4 of U11 on 1A and 1B which sets IOenable to HI , ie turns it off. That in turn sets RAM enable at the PAL chip ON. If you cant do that, you cant peform a RAM test. just in case it helps , on maygay RAM sits at 0000-1FFF, the IO sits 2000-27FF and the ROM fills the address space after that (2800 and up)

I started my first board tonight here's where I'm at. I'm planning to repair the tracks, refit new IC's when they turn up. One repair needs to go through the via onto the back. Change that diode on D30 to a 1N. Change the old transistor q1. Try it Open to any suggestions as usual. Also looking for the hex file of the m1b test Rom. Thanks

You Should be able to just save the images and print them out?

Thanks very much mate....so useful!

There was a deal a while back between Paul knowles and someone else on Facebook there were a few system 5s.. I think this was one of them?

yes i see it and its broken look how much its on

this might be of help @MattyL