520ST fully working and upgraded

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rubber_jonnie
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520ST fully working and upgraded

Post by rubber_jonnie »

A while ago, I got a 520ST from exxos, knowing full well it wasn't quite right, and prepared to have a go at bringing it back to life. It seemed the right thing to do, because cosmetically it was in very good order.

So first off I resolved the problem of no PSU by building one (https://www.exxosforum.co.uk/forum/viewt ... &hilit=PSU), then resolved the problems with RAM. There was track damage due to a piggyback expansion, and in the end I felt it was simpler to remove all the RAM and fit a SIMM adapter to the MMU and Shifter, so having done that the machine was finally booting to desktop.

That left two problems:

1. The floppy drive didn't work,and any attempt to access a disk crashed the machine.
2. The TOS was version 1.00.

I'm happy to say the day is finally here where there are no problems left :)

I thought I'd tackle the FDD problem first, since I knew the machine was working upto getting a desktop.

That's where the diag cart came in, and on running a floppy test, this was the result:

Diags.jpg
Diags.jpg (89.82 KiB) Viewed 3408 times

Having already tried swapping the DMA, FDC and YM chips for known good items, they were ruled out, leaving the GLUE and MMU. Since the MMU had a memory adaptor plugged in, it had to be GLUE first, and lo and behold, with a replacement GLUE installed, the FDD sprang back into life :) I'll test the GLUE on another machine, but it certainly looks like it's had it's day.

Success.jpg
Success.jpg (63.15 KiB) Viewed 3408 times
The TOS upgrade was simple. I sourced some PROMS from evilbay, and split a TOS 1.04 image using ROMSPLIT on Hatari to get the 6 ROM images I needed and burned them.

Once swapped out,everything worked like a charm.

Working.jpg
Working.jpg (116.75 KiB) Viewed 3408 times

And I'm very happy to have this lovely machine back in the land of the living. I'll get it back in the case, hopefully tomorrow, but I think I'd better have a dig for some 1MB SIMMs and see how it likes 4MB first :)

I guess it might also be worthwhile seeing how it likes SMonson's DVI adapter whilst the lids off 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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PaulJ
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Re: 520ST fully working and upgraded

Post by PaulJ »

Nice work @rubber_jonnie .. :cheer:
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exxos
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Re: 520ST fully working and upgraded

Post by exxos »

:bravo:
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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PhilC
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Re: 520ST fully working and upgraded

Post by PhilC »

Well done @rubber_jonnie . Always fancied one myself too. Will keep a look out I guess.
If it ain't broke, test it to Destruction.
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rubber_jonnie
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Re: 520ST fully working and upgraded

Post by rubber_jonnie »

@PhilC They are lovely machines 😁
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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PhilC
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Re: 520ST fully working and upgraded

Post by PhilC »

rubber_jonnie wrote: Sat Feb 01, 2020 9:21 pm @PhilC They are lovely machines 😁
A bit more of a challenge to upgrade but that's part of the fun.
If it ain't broke, test it to Destruction.
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rubber_jonnie
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Re: 520ST fully working and upgraded

Post by rubber_jonnie »

And here we are back together and playing nicely :)

Reassembled.jpg
Reassembled.jpg (100.99 KiB) Viewed 3325 times
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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