Leaderboard

this was the mpu3 ram, designed in diptrace of course the sys80! then there was the JPM system 5 add on board to convert non Yamaha boards to Yamaha sound! but the drawing was as far as this project went, there was just no market for it when I did it! same with the token to cash boards prototype diptrace design made pcb's and finally the 'never actually needed' pc92 reset, diptrace did a good 3d model before the boards were made! and the most complicated! a 4 layer video card! could not buy one so had to make it myself! only 20 ever made!

Maybe not lost if the roms are required I'll upload them once it's arrived

I've repaired the board in question what I call a total rebuild all meter and reel index completely gone rubbed out with the fibre glass pencil like arubber to a pencil on paper. It's the one I put aphoto up of .I like to think I've done a thorough job I guess time will tell . I've told Chris about the battery I've put it on wires with terminal blocks I'm sending a coin cell board with diode on board I've made with wires the coin cell has lasted amonth now on this one an is just under 3v still. if he doesn't want the coin cell board he just unscrews it and his mate puts wires in the proper battery when he gets it an just screws that in instead. So I don't know why were having this chat about the battery

would be nice if it was spelled out for us!!

Oh and if the B+ rail on a monitor is too high by only 10v the high voltage can shoot to over 30kv, so then at that voltage the crt produces a good few x rays!! And x rays on the bollocks makes you sterile!!! No such thing as health and safety back then!!!! you can see why I isolate the high voltage stage to check the psu voltages now!!!

Crt’s have around 24kv to 28kv no such thing as discharge circuits when it’s turned off! If your lucky they do discharge over a day or so, if unlucky they can still bite with around 8kv sitting there to catch you out!!! (8kv = 8000v and 24kv =24000v) beware of crt monitors!! It’s only us crazy guys bought up on having to repair them that are still silly enough these days to still do so lol

Not at all!!! It’s what I have learnt when messing with batteryless ram stuff some years back, and of course more interesting to me was the way it wrote to the ram! Has to be the right sequence for the batteryless ram to work!! All a minefield!!