Fixing my C128D

[rubber_jonnie]

@rubber_jonnie haven't found any under sockets on this board so far but have found a few soldered pins that were left too long and just about touching the one next to it, that and the case of the rust monster leaving his foot prints everywhere.

Once I’ve got this board booting again I’m sealing the whole thing with some pcb lacquer.

Hopefully the 8502 comes tomorrow.

I hate the poorly trimmed legs on parts, so unnecessary. Lacquer sounds like a great idea.

[stephen_usher]

@rubber_jonnie haven't found any under sockets on this board so far but have found a few soldered pins that were left too long and just about touching the one next to it, that and the case of the rust monster leaving his foot prints everywhere.

Once I’ve got this board booting again I’m sealing the whole thing with some pcb lacquer.

Hopefully the 8502 comes tomorrow.

I hate the poorly trimmed legs on parts, so unnecessary. Lacquer sounds like a great idea.

Just be thankful if you don't have both bent and trimmed legs! They're hell to desolder.

[PhilC]

@stephen_usher uouve just described how all large chips were soldered in and a real pain yo get out.

[stephen_usher]

@stephen_usher uouve just described how all large chips were soldered in and a real pain yo get out.

Yikes! I've only seen it done in a TI 99/4A with all the 4116 RAM.

[PhilC]

My 8502 & MMU arrived today and have been fitted. I don't think the MMU made any difference at all but now with the new 8502 I have more address bus activity but some odities as well. For instance activity on A6,A8 & A10 but not on A5, A7, A9, I'm going to see what 74 chips are on the odd side of the circuit and see what happens.

the rom chips are also very warm, so since its an odd address bus fault it might be one of those?

[rubber_jonnie]

My 8502 & MMU arrived today and have been fitted. I don't think the MMU made any difference at all but now with the new 8502 I have more address bus activity but some odities as well. For instance activity on A6,A8 & A10 but not on A5, A7, A9, I'm going to see what 74 chips are on the odd side of the circuit and see what happens.

the rom chips are also very warm, so since its an odd address bus fault it might be one of those?

Would be worth pulling the ROMs to see if the address bus improves.

[PhilC]

My 8502 & MMU arrived today and have been fitted. I don't think the MMU made any difference at all but now with the new 8502 I have more address bus activity but some odities as well. For instance activity on A6,A8 & A10 but not on A5, A7, A9, I'm going to see what 74 chips are on the odd side of the circuit and see what happens.

the rom chips are also very warm, so since its an odd address bus fault it might be one of those?

Would be worth pulling the ROMs to see if the address bus improves.

There was some inconsistent improvement, so I am going to program up a few replacement roms and see what happens.

[rubber_jonnie]

Would be worth pulling the ROMs to see if the address bus improves.

There was some inconsistent improvement, so I am going to program up a few replacement roms and see what happens.

Good luck. Are there any pullups for the address bus that might have gone bad?

[PhilC]

@rubber_jonnie There are pull-ups but I've checked all of those with the power off and they all pull up to 5V when pressing reset.

[rubber_jonnie]

@rubber_jonnie There are pull-ups but I've checked all of those with the power off and they all pull up to 5V when pressing reset.

Ahh well, worth a go.