Leaderboard

Yes the problem was outside what I though was the damage area! It does show you have to be so careful to get all the damage! Every board I do seems to throw up something different, that's why cannot just say "oh just change this or that component" as it seems to me never to be as easy as that on Maygay M1 boards! each board has to be looked at on its own merits! I don't socket the chips. only what is already socketed like the PAL chip as that was originally socketed and can easily fail!, as you can see in the picture below the cpu is removed for a second time and I have no problem removing chips that I have already taken out once to have to remove yet again, so for me sockets are not required! as the chip legs are flat I can easily fit 2 of the 0.25mm wires one in front and behind the chip leg passing through the holes with no problems and if needed remove the chips again once soldered in without damaging the wires! if turned pin sockets are used these would fill the holes up leaving no room for the wires, also sockets raise the chips up so when the program card sits over them it then hits the chips and doesn't allow the program card socket to seat properly, so all that means I don't bother with sockets as I don't have the need to! So for your entertainment this is how the CPU area looks tonight after some more wire bridges have been done! taking no chances and done more than just the one! the bad open circuit one I have circled in blue so you can see where it was.

wouldn't that be nice!!! well this was difficult to see! on max magnification (x60) you can only "just" see the green corrosion line at the top of the via!! That's enough for tonight!!

So! have been measuring continuity between various chips to see if I could narrow this down, after a good while found open circuit between Pin 1 of U11 (74hc259) ad pin 1 of U34 (MC68681) tracing this round the board the continuity disappeared right by the processor and right by a via! You can see my meter probe mark on the via, and if you look closely between the 2 pins of the processor chip, where the copper is showing through the red solder resist, so the open circuit is very much the same as the vias earlier, just where the track emerges from the solder resist! So looks like the processor will have to come out again and that area given a through going over for rot repair too!

Yeah I really hope this one works first attempt. M1's do seem to have the most magic when one fires up. Are you going to film it firing up? Thanks for the tips... after reading I realised that 74hc was the family. Now learned what the H&C are for off the back of that. Sounds stupid but until someone tells you...it's difficult to understand. I managed to get enough for 5boards and fitted sockets on the first one as I don't have an ic tester. Are there any other weaker IC on the boards? I have got some cpu's but I'm not to sure on most of the other ic. A fair few look like they're driving...

Yes Bob! and that's exactly what happened! the board sadly did not burst into life!! the main CPU oscillator is there all ok! so is the reset line pulsing, address lines on the CPU all as expected ramping up binary counting! but data lines nada! (that's why its binary counting on the address lines!) CPU removed and is blameless! next the 68681 as have had a fair few of these Motorola chips fail! pin 40 when it desoldered was loose and fell out of the board! chip examined and sure enough the board must have taken a hit or something in the past and pin 40 is clean off the chip! pin 40 is the power to the chip! perhaps this is the fault????? we will see!

Board now baked, covered with solder resist to protect and dried! I like it when I get to this stage!

Coming soon, one set on 2p with the jackpot at £1 other set on 20p with the jackpot at £4.80.