Fixing my C128D

[mrbombermillzy]

Keep going Phil.

Sooner or later you will get there.

(Could really do with a 'busy soldering' smilie, but you get the jist.)

[PhilC]

Still waiting for the power switch but in the meantime I fitted the modulator replacement. It gives me an S-VHS out and headphones out on top of everything else. I’ll eventually fit it to the C128D as well.

So I also couldn’t wait for the power switch to arrive and bridged the connections so I could try and get the board up and running.

The bad news is that it’s still not booting but the good news is that all of the address bus is now working as it should and I think I’m finally in a position where I can track down what else is going on.

I am still going to socket the rest of the 74 series chips and Ram but want to see if I can get it to boot beforehand. Might be nice to take two C128s to Cyber Legends perhaps?

[PhilC]

Going to park this repair for a bit as it’s taking up too much time and I have stuff to do for Cyber Legends ready for next weekend.

It is in a position where I’ve got rom and ram access and it switches from the Z80 to the 8502 but then doesn’t
Do anything after that and the screen stays black.

[rubber_jonnie]

You sound really close to fixing it, looking forward to that happy day

[PhilC]

You sound really close to fixing it, looking forward to that happy day

Yes I think I am but maybe have a track or two that may be broken and can't find them by scoping alone.

[PhilC]

Had another go at fixing this yesterday, I did find a couple more faults.

Found some more dry joints and the big was finding a factory bodge wire that was soldered to one pin and the pin next to it had pierced the insulation causing D7 to have a 5V pull-up when none should be fitted. I had to take out all of the chips and then some to track that one down.

I'm just doing this repair in small stints from now on as it ends up taking up a lot of my time having to go over old stuff too see what's changed after each fix.

Not given up yet, just paused for thought.

[PhilC]

Not had a great amount of time to look into this lately but noticed that there is a GitHub for a replacement C128 motherboard, so considering how much corrosion is on this board I’ve decided to order a couple of those and will build them up as a replacement for the one in my C128D to future proof it a bit more hopefully.

If this is something you’re interested in, the GitHub is here:

https://github.com/jgrip/open128

[rubber_jonnie]

Not had a great amount of time to look into this lately but noticed that there is a GitHub for a replacement C128 motherboard, so considering how much corrosion is on this board I’ve decided to order a couple of those and will build them up as a replacement for the one in my C128D to future proof it a bit more hopefully.

If this is something you’re interested in, the GitHub is here:

https://github.com/jgrip/open128

That's a good project, it really is great the number of modern replacements that can be had these days.

[PhilC]

So I'd ordered a couple of PCBs from an online seller which never turned up so just got a refund.

I've checked on JLC and to order 5 of them including postage, tax etc is going to be around £60. So I'll probably have to wait for payday for that as I've spent too much already this month.

[rubber_jonnie]

So I'd ordered a couple of PCBs from an online seller which never turned up so just got a refund.

I've checked on JLC and to order 5 of them including postage, tax etc is going to be around £60. So I'll probably have to wait for payday for that as I've spent too much already this month.

I know that feeling...