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It certainly was. The only other thing in that region of the address bus is the PLA, so hoping that's not failed too.rubber_jonnie wrote: 14 Sep 2023 16:34Ahh well, worth a go.PhilC wrote: 14 Sep 2023 16:34 @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.
PLA would be bad news...PhilC wrote: 14 Sep 2023 16:37It certainly was. The only other thing in that region of the address bus is the PLA, so hoping that's not failed too.
Well it's good that you have a possible culprit, not so good it's the PLA. Is it a C128 specific one, or standard C64 PLA?PhilC wrote: 14 Sep 2023 19:19 Did a bit more scoping and testing of the roms. The roms all read fine into my TL866 so I'm going to rule them out at least for now.
I removed the PLA to socket it like the rest of the large chips and thought what the heck, lets see what the address bus does with it removed and unfortunately, it looks like the PLA has also gone pop as the address lines pull-up, then pulse for a second or two and then go to 0V which they didn't before.
I'm really hoping this is the end of the chip purchases for this C128D as its been pretty expensive so far.
I did see that but fortunately I found a seller on eBay with them, so I’ve bought 3 of them, one for this C128 and the other two for stock should I ever need to fix another one.stephen_usher wrote: 14 Sep 2023 22:05 It's not the same as the C64.
There is a modern replacement but it's from the USA and would be mega expensive unfortunately.
Yeah, spares are becoming a bit of an issue, and whilst there are some good solutions out there, they don't cover every chip we might need. Good to have some stock.PhilC wrote: 15 Sep 2023 08:06I did see that but fortunately I found a seller on eBay with them, so I’ve bought 3 of them, one for this C128 and the other two for stock should I ever need to fix another one.stephen_usher wrote: 14 Sep 2023 22:05 It's not the same as the C64.
There is a modern replacement but it's from the USA and would be mega expensive unfortunately.
Ironically the only chip I purchased that I haven’t needed is the VIC - II but it’s good to have spares if all the big chips.
Keeping my fingers crossed :)PhilC wrote: 17 Sep 2023 10:08 Really quick delivery from the EBay seller and the PLA chips arrived yesterday but I was out all day as it was the grandsons birthday.
Got a bit of DIY to do and then later on I’m hoping to power up the C128D with the new PLA fitted and see what happens.