Brett's STE - Repair thread

[rubber_jonnie]

Those are very chunky wires. :-)

I usually use wire wrap wire as it's only "low speed" signalling.

It was that or kynar, I have nothing in between, and the kynar is a bit fragile tbh, but the stuff I used usually works just fine 😁

[stephen_usher]

No sacrificial ribbon cable? :-)

Actually, the insulation would make it a bit stiff to use.

[rubber_jonnie]

No sacrificial ribbon cable? :-)

Actually, the insulation would make it a bit stiff to use.

I did consider it, but too much of a faff to separate, cut to length and strip!

[derkom]

I have some 34 AWG wire with teflon insulation I use for such things. I find that for such short runs, regular insulation ends up melting too much. I screwed up a few tracks on my H4 and built some bodges on the bottom with this stuff and it's worked just fine.

[rubber_jonnie]

I have some 34 AWG wire with teflon insulation I use for such things. I find that for such short runs, regular insulation ends up melting too much. I screwed up a few tracks on my H4 and built some bodges on the bottom with this stuff and it's worked just fine.

This particular wire is quite resistant to melting, and in general is quite good for 'bodge' wiring, but the whole experience has me thinking I should get something of a slightly thinner gauge than this.

The kynar wire I have is too fragile and the insulation too easy to melt, so something like wire wrap wire would probably be best, but I do like the idea of teflon coated wire.

[rubber_jonnie]

Ok, so all of the connections seem to be there at the sockets now, but I'm convinced I missed something as it still doesn't boot, so next time I'll need to check every last connection against the schematic, but time for a break to do some of my own stuff, notably the Aquarius Micro Expander.

What is interesting is that I can see activity on pins at boot/reset whereas before there was nothing. Still nothing from the diagnostic cart either. I think I've made good progress over the weekend though.

[stephen_usher]

Can you see data on the data bus elsewhere, far from the ROMs, such as on the legs of the data line pull-ups? This should show if you have proper connectivity. After all, the ROMs have nothing but the enable pins, address bus, data bus and power.

(I'm assuming that you've already scoped the address pins on both ROMs.)

[Badwolf]

What is interesting is that I can see activity on pins at boot/reset whereas before there was nothing. Still nothing from the diagnostic cart either. I think I've made good progress over the weekend though.

The check for the cart is *really* early on in the boot process, IIRC. So early in fact that my first thought is probably invalid, but I'll mention it anyway:

Check the level of BR, BG and BGK lines: the DMA chip lies beyond the ROMs and if, for example, BR is stuck low, you may not get very far as the CPU could be relinquishing the bus before it gets up to any actual work.

BW

[rubber_jonnie]

Can you see data on the data bus elsewhere, far from the ROMs, such as on the legs of the data line pull-ups? This should show if you have proper connectivity. After all, the ROMs have nothing but the enable pins, address bus, data bus and power.

(I'm assuming that you've already scoped the address pins on both ROMs.)

No, but it is on the to do list, I stopped to do some of my own stuff as I'd spent a long time on this already this weekend. I'll cross check with my working machine anyway so I have a good reference.

Appreciate the input :)

[rubber_jonnie]

What is interesting is that I can see activity on pins at boot/reset whereas before there was nothing. Still nothing from the diagnostic cart either. I think I've made good progress over the weekend though.

The check for the cart is *really* early on in the boot process, IIRC. So early in fact that my first thought is probably invalid, but I'll mention it anyway:

Check the level of BR, BG and BGK lines: the DMA chip lies beyond the ROMs and if, for example, BR is stuck low, you may not get very far as the CPU could be relinquishing the bus before it gets up to any actual work.

BW

Thanks, I'll give that a try and compare to my working machine. Appreciate the input :)