Mrbombermillzy's box of delights

[mrbombermillzy]

OK, cool and good to know. I'm in the office today so not much chance to look at anything, but sounds like that part of things is done then. Unless you want me to flash firmware and test it?

I think youve done enough, thanks.

I'm hoping to get the CPU on the PC Speed done tomorrow evening, from what I can see what you've said, the wiring on the card shouldn't affect the base board if the jumpers are left open.

I think it's just some sort of reset. We'll see once the CPU is swapped.

My thoughts exactly. It doesnt seem to be needed for the basic running of the card at least, so should be fine 'as is'.

After that I'll do the dual shifter soldering then I can start to look at the C64 DTV's.

Woohoo.

[rubber_jonnie]

Desoldering gun cleaned and ready for duty removing the CPU later

[rubber_jonnie]

OK, so the CPU came out nice and clean and easy:

IMG20250814120140.jpg (424.18 KiB) Viewed 376 times

And the socket is in with the new CPU. Sadly it isn't a CPU issue it would seem. I need to have a look now at the board compared to mine, which does work.

If I can't find anything bad it may be the case that one of the logic IC's is bad or one or more of the GALs has failed. PCB review first though.

@mrbombermillzy The CPU you sent is an NEC V30, but do you know for sure if it is serviceable? I might be able to test it, let me see what I can do.

[mrbombermillzy]

Thats annoying.

Sorry Jon, I only have the ebay sellers word (years ago) that the CPU was working, so probably no real guarantees that its ok.

Either that or like you say, the card could have logic problems.

I was expecting the card to work at this stage, so if you dont feel like continuing, thats quite alright.

However, if you think that you can diagnose/fix fairly easily (by swapping out/cross checking with your board or whatever) and are happy to do so, then thats wonderful. But please dont feel obliged to.

[rubber_jonnie]

Thats annoying.

Sorry Jon, I only have the ebay sellers word (years ago) that the CPU was working, so probably no real guarantees that its ok.

Either that or like you say, the card could have logic problems.

I was expecting the card to work at this stage, so if you dont feel like continuing, thats quite alright.

However, if you think that you can diagnose/fix fairly easily (by swapping out/cross checking with your board or whatever) and are happy to do so, then thats wonderful. But please dont feel obliged to.

Well, I think I have an idea of what's going on. When looking at it with my thermal camera, the card is cold, like it has no power. When I drop mine in, you can see ICs warming up even when it's still in ST mode.

It does this with either the CPU in or out, so it could be a short or it could be a dodgy 5v connection. It should pick up 5v from the ST CPU socket.

[mrbombermillzy]

When looking at it with my thermal camera, the card is cold, like it has no power. When I drop mine in, you can see ICs warming up even when it's still in ST mode.

It does this with either the CPU in or out, so it could be a short or it could be a dodgy 5v connection. It should pick up 5v from the ST CPU socket.

Its very lucky that - purely by chance it would seem - that you have the very same card, so fault finding is made easier.

But yes, I agree. If nothing is being powered then it does look like the voltage coming in is the source of the problem.

A case of continuity testing and backtracking through the 5v line perhaps?

[rubber_jonnie]

OK, I think power was a red herring, but still not certain, however I have found something interesting:

IMG20250814150228.jpg (249.99 KiB) Viewed 361 times

Zoom in. and you'll see a cut track. It seems that the purpose of these jumpers:

IMG20250814154445.jpg (326 KiB) Viewed 361 times

Is to join them up, but I just don't get why, or what the other jumper is used for. However, with the jumper in position it should behave as mine does, but it just crashes.

A cursory look at the board and comparing to mine shows nothing other than that, and I'm thinking that the GALs have an issue now, so removing them maybe next on the to do list to see if they need reflashing.

I have checked the tantalums BTW and none are shorted.

[rubber_jonnie]

Its very lucky that - purely by chance it would seem - that you have the very same card, so fault finding is made easier.

But yes, I agree. If nothing is being powered then it does look like the voltage coming in is the source of the problem.

A case of continuity testing and backtracking through the 5v line perhaps?

Yes, pretty handy that.

It has also occurred to me that it may be worthwhile removing the mods and setting up identically to mine. it is possible that the pins headers don't work well with my socket, they are pretty loose, and there could easily be solder whiskers under the pin headers or under the socket.

My machine has the socket mounted on top of the CPU so just sits on top of that. I can if you want revert your PC Speed to be like mine and replace all the pin headers with better ones than you currently have.

That wouls just mean that you lose the socket on top, but removing the mods would make troubleshooing much easier.

[mrbombermillzy]

Of course. Ditch the mods. Do what you need to do.

Thank you for thoroughly going through the board like this.

[rubber_jonnie]

Of course. Ditch the mods. Do what you need to do.

Thank you for thoroughly going through the board like this.

That's fine, it's a but of fun and enjoyable

I will get the mods pulled and put it back to the same config as mine, be easier to compare then too.

What I've also realised is that it is behaving like the ST has no CPU installed, so very possibly poor contacts.