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 »

BrettRogersUK wrote: Wed Jan 26, 2022 4:27 pm I've enjoyed watching this journey. Really been an eye opener to see what can be done with the proper equipment. Look forward to seeing more! Looks like your making some progress at least looking at those pics from the LA.

Regards,

Brett
:)

It has taken me a long time to acquire all the gear, and be able to repair these things, but thankfully some of it is so much cheaper than it used to be. Don't forget, I am an amateur at this, it isn't my day job and I couldn't design anything electronic for toffee, but I do enjoy it :)

We're still not out of the woods yet, but at least I can see just what is going on at the ROMs.

Bad address = data from the wrong place = CPU going into a /HALTed state. It all adds up, but more work to be done, at least I have a target now.
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...
BrettRogersUK
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Re: Brett's STE - Repair thread

Post by BrettRogersUK »

rubber_jonnie wrote: Wed Jan 26, 2022 4:32 pm :)

It has taken me a long time to acquire all the gear, and be able to repair these things, but thankfully some of it is so much cheaper than it used to be. Don't forget, I am an amateur at this, it isn't my day job and I couldn't design anything electronic for toffee, but I do enjoy it :)

We're still not out of the woods yet, but at least I can see just what is going on at the ROMs.

Bad address = data from the wrong place = CPU going into a /HALTed state. It all adds up, but more work to be done, at least I have a target now.
You've got further than me. I just hit a dead end because I hadn't got the hardware to test it to find out what you've found. I look forward to seeing your progress.

Regards,

Brett
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Re: Brett's STE - Repair thread

Post by rubber_jonnie »

BrettRogersUK wrote: Wed Jan 26, 2022 4:38 pm
You've got further than me. I just hit a dead end because I hadn't got the hardware to test it to find out what you've found. I look forward to seeing your progress.

Regards,

Brett
For stuff like this, you do really need the gear, or you have no idea what's going on. There was a time when I wouldn't have attempted it, and there is still so much I don't know, but weirdly, this is fun for me :)
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 »

Well, with the knowledge you have now you could definitely design digital electronic stuff. It's basically electronic Lego. You just need to know a few rules of thumb really about bypass caps, pull-ups and basic logic (and gates, inverters, not gates etc.). It's mostly, "if you do this, that happens".

Even the basic timing stuff isn't that hard. e.g. if you need a delay between /CE and /OE pass the /CE through a couple of inverters to delay it a few nanoseconds and Bob's your Aunty. (With memory (ROMs and SRAM) you have to remember that /CE primes things, getting everything ready and /OE just opens the gates to let the data in/out.)
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.
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Re: Brett's STE - Repair thread

Post by stephen_usher »

rubber_jonnie wrote: Wed Jan 26, 2022 4:41 pm For stuff like this, you do really need the gear, or you have no idea what's going on. There was a time when I wouldn't have attempted it, and there is still so much I don't know, but weirdly, this is fun for me :)
Indeed. Without the correct tools you get nowhere. Once you have them it's just a puzzle where you follow the clues, which is the fun/infuriating bit.
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: Wed Jan 26, 2022 4:43 pm Well, with the knowledge you have now you could definitely design digital electronic stuff. It's basically electronic Lego. You just need to know a few rules of thumb really about bypass caps, pull-ups and basic logic (and gates, inverters, not gates etc.). It's mostly, "if you do this, that happens".

Even the basic timing stuff isn't that hard. e.g. if you need a delay between /CE and /OE pass the /CE through a couple of inverters to delay it a few nanoseconds and Bob's your Aunty. (With memory (ROMs and SRAM) you have to remember that /CE primes things, getting everything ready and /OE just opens the gates to let the data in/out.)
You know maybe I should just try!!
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 JezC »

@rubber_jonnie Go on - you know you want to!

:poke: :hide: :fire: :fire: :fire:
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Re: Brett's STE - Repair thread

Post by rubber_jonnie »

JezC wrote: Wed Jan 26, 2022 5:56 pm @rubber_jonnie Go on - you know you want to!

:poke: :hide: :fire: :fire: :fire:
Not you too!!
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 »

I'm feeling like a minor celebration. I traced A1 and found that it should be connected to pin 2 of the DMA. Only it wasn't, so I hooked it up and I now get this:

IMG_20220126_230722.jpg
IMG_20220126_230722.jpg (281.25 KiB) Viewed 1171 times

Which I am going to take as progress since it looks like something is getting to video RAM, something I'd not seen before.

Clearly some work left to be done, but the little red led on my diag cart which shows ROM access is now flickering, a good indicator that ROM access is at least being tried. It was completely dead up until now.

Clearly something is going on and it is trying, so more checking to be done, I'll need to look at A2 next.

I also added some test points near the GST combel and I can see that A1 & A2 are connected all the way from there to the Blitter, the CPU and finally the ROM and A1 to the DMA. I am also seeing address line pulses all the way through now too.

More to do though, @exxos another one for your crash screen archive :)
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 exxos »

Nice! Test cartridge run yet ? :hide:
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
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