Brett's STE - Repair thread

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rubber_jonnie
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Re: Brett's STE - Repair thread

Post by rubber_jonnie »

stephen_usher wrote: Sat Jan 15, 2022 6:20 pm 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 😁
Collector of many retro things!
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Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
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Re: Brett's STE - Repair thread

Post by stephen_usher »

No sacrificial ribbon cable? :-)

Actually, the insulation would make it a bit stiff to use.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
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Re: Brett's STE - Repair thread

Post by rubber_jonnie »

stephen_usher wrote: Sat Jan 15, 2022 10:12 pm 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!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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Re: Brett's STE - Repair thread

Post by 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.
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Re: Brett's STE - Repair thread

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derkom wrote: Sun Jan 16, 2022 9:38 am 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.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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Re: Brett's STE - Repair thread

Post by 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.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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Re: Brett's STE - Repair thread

Post by 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.)
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
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Re: Brett's STE - Repair thread

Post by Badwolf »

rubber_jonnie wrote: Sun Jan 16, 2022 3:11 pm 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
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Re: Brett's STE - Repair thread

Post by rubber_jonnie »

stephen_usher wrote: Sun Jan 16, 2022 3:38 pm 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 :)
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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Re: Brett's STE - Repair thread

Post by rubber_jonnie »

Badwolf wrote: Sun Jan 16, 2022 4:08 pm
rubber_jonnie wrote: Sun Jan 16, 2022 3:11 pm 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 :)
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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