Mrbombermillzy's box of delights

[rubber_jonnie]

OK, so I was about to get busy removing the mods and took another look and wen't back to my theory that maybe the connections were bad after test fitting some pin headers in the CPU socket.

It turns out the pin headers weren't long, they are just very tight and after pushing them in really quite hard, the machine now boots up with your PC Speed installed. It boots with either the jumpers on pins 1&2 or 2&3.

I think they were likely soldered on by hand and as a result are not well aligned with the socket.

The bad news is that PC Speed just hangs when I try to run it, so while I no longer think removing the mods is necessary, it now points to either a bad CPU (I've tried both), bad GALs or bad logic IC's.

I am considering running mine for a while to see what the thermals look like, then try to boot yours, leave it hanging and see what we see.

It's certainly quite positive and I think probably easily fixable.

[mrbombermillzy]

Well I will both apologise for it not being straightforward and thank you for jumping down the rabbit hole with this one. :D

Looks like you have got a good grip on the issue.

It will be very interesting to seeing what transpires.

[rubber_jonnie]

Well I will both apologise for it not being straightforward and thank you for jumping down the rabbit hole with this one. :D

Looks like you have got a good grip on the issue.

It will be very interesting to seeing what transpires.

No problem, no need to apologise, it's what I signed up for.

I need to find a less aggressive way to get the board attached to the CPU I think, mine fits a lot easier (The Vortex does too). I want to avoid having to press down so har to install, so I may fit another CPU and socket so I have just the CPU to deal with and I just have to replace one whole unit at a time. I have spare CPUs so not a problem.

Now we know the files are available for the GALs it's something at least can easily be fixed if needs be. I may also see if I have another V30 to hand to try and verify the CPU side of things.

BTW I have also soldered up the dual shifter, though I'm not really in a position to test it.

[rubber_jonnie]

OK, so last post on this for tonight.

I did as planned and now have a CPU attached to the PC Speed (Both actually) as it is far easier to change the CPU without putting extreme amounts of pressure on the board, meaning swapouts are quick and easy.

Still doesn't work but does now boot into TOS and running PC Speed does try to start, it just hangs slightly before it would normally drop into a prompt for a DOS disk.

I got the scope out and see what appears to be address line activity and there is a good 8Mhz clock signal - this matches what I see on my working PC Speed.

So I think it's down to logic IC's and GALs now. Since I have the files for the GALs now, and some spare IC's I think I'll pull them out next as a lot of the logic is HC types I don't have. I also think a GAL fail is more likely to be the cause.

I will socket them, and fingers crossed I may just be able to re-write them, but I do at least feel I am hot on the trail :)

It's been fun doing some ST related stuff, it's been a while.

I had hoped to test the CPU's in my Book 8088 but they are V30's, so an 8086 and they are not interchangeable with the V20 in my Book 8088 - the name is a bit of a giveaway too...

[mrbombermillzy]

You are like a powerhouse getting things done quickly. I can barely keep up! :lol:

BTW I have also soldered up the dual shifter, though I'm not really in a position to test it.

Thats wonderful. Thank you. I can finally dig out and transfer my matching shifters from the prototype now. :dualthumbup:

I got the scope out and see what appears to be address line activity and there is a good 8Mhz clock signal - this matches what I see on my working PC Speed.

So I think it's down to logic IC's and GALs now. Since I have the files for the GALs now, and some spare IC's I think I'll pull them out next as a lot of the logic is HC types I don't have. I also think a GAL fail is more likely to be the cause.

I will socket them, and fingers crossed I may just be able to re-write them, but I do at least feel I am hot on the trail :)

It's been fun doing some ST related stuff, it's been a while.

Great bit of work here Jon. Im sure it will get there soon. :) Although Id say its more PC related work than ST? :lol: :hide:

I had hoped to test the CPU's in my Book 8088 but they are V30's, so an 8086 and they are not interchangeable with the V20 in my Book 8088 - the name is a bit of a giveaway too...

I agree; its a shame. However 16 into 8 bits just wont go. :)

As an aside, the guy who created the original MCL-64 (Ted Fried) has also recreated the V20. Apparently, it runs at speeds approaching 80386 territory!:

https://microcorelabs.wordpress.com/202 ... m-microsd/

[rubber_jonnie]

You are like a powerhouse getting things done quickly. I can barely keep up! :lol:

No problem, I'm just trying to blast through as much as I can before I go on holiday in a week.

Thats wonderful. Thank you. I can finally dig out and transfer my matching shifters from the prototype now. :dualthumbup:

I'd be interested in how you get on with it.

Great bit of work here Jon. Im sure it will get there soon. :) Although Id say its more PC related work than ST? :lol: :hide:

Fingers crossed :) It is a bit of a hybrid isn't it?

I agree; its a shame. However 16 into 8 bits just wont go. :)

As an aside, the guy who created the original MCL-64 (Ted Fried) has also recreated the V20. Apparently, it runs at speeds approaching 80386 territory!:

https://microcorelabs.wordpress.com/202 ... m-microsd/

Indeed they don't...

Will have a look at that V20 thing, sounds interesting.

[rubber_jonnie]

OK, so it doesn't look like its the GALs....

One thing, I couldn't read the old GALs, they weren't recognised in my reader and some pins were not detected. With that in mind I couldn't reprogram them, could be they have security set on them.

I've dropped some spares of mine in, but no difference so I need to move to the logic ICs next.

[rubber_jonnie]

OK, so post lunchtime update.

I pulled the CPU from my card and installed a socket, all tested good afterwards with my CPU. What I wanted to do was verify your CPU one way or the other and I can say for certain that both of your CPUs work just fine.

That really narrows things down as it just leaves 3 74HC373's and a single 74LS368.

I might have the LS but I don't have the HCs, so I will see what I have in my parts bin and replace the LS if I have one, and then order the HCs if it's still broken afterwards.

I'll update when I've been through my incredibly untidy drawer of IC's...

[rubber_jonnie]

OK, so it isn't the 74LS368 either, so that just leaves the 74HC373's, which I will need to order, and in the meantime I'll lift the IC's and install sockets. That will also give me a chance to run the 373's through my TL866 and see if they come back as good or bad.

EDIT: 74HC373's are on order.

[rubber_jonnie]

Hmm, interesting. So I tested the 74HC373's in my TL866 and they are supposedly good... I suppose they could be marginal, we'll see with the new ones.

So if all the logic ICs are good, the CPU's are good, that takes me back to the possibility that there is something to do with the MODs that are casuing the issue, so I think I will need to remove them so I can have a good look for PCB damage and do a close comparison with mine.