Mod #1 The STE

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Joined: Tue Dec 19, 2017 2:16 pm

Mod #1 The STE

Post by braincell »

After a few years away from a physical atari i stumbled across Flash Floppy and the exxos webstore and decided to give some of my ataris some tlc in the hopes they survive a while longer, having 2 STE's and 2 STFMs in the loft i decided to set one up for some captive / dungeon master goodness. Turns out i had a near mint FM in the loft so i dragged that down for some upgrades too. My 2 STE's are still in the loft as i came across a listing on Amibay for a STE and Ultrasatan for 130 quid..... How could i pass this up.

The STE arrived in very good condition and colour with 4 megs already in it, But the internal power molex connector had been butchered into a splice with a micro-usb connector dangling out the back from between the casing, this had come loose in transit and would no doubt be shorting against something so i repaired this first then booted it up...... All looked good with the supplied scart cable on my flat screen TV.

I had ordered a couple of Gotek drives for testing with flashfloppy and i was amazed how well they worked......My st's in the loft have HxC units that i had to pay for the firmware......

So, Armed with a free firmware floppy alternative my first stumbling block was the fact you needed a floppy cable extender.....I broke out the CAD software and quickly knocked up a mount to hold the Gotek board upside down thus no more need for a floppy extender and twisting the cable.

(I have put these up on thingiverse...... Search atari / Gotek)

I quickly realised that i could add some features.... So i did an OLED version and quickly expanded that to include relocating the mouse joystick ports too moving the OLED to the top of the case.......

I ordered an exxos psu and also a psu cap kit and 1 meg of chips for the fm....... from the exxos webstore and set about modding this bad boy......

On a side note i had a bloody good read of the ST "bad" dma article on the site (was of particular interest now i had an ultrasatan) .... Like many people i blindly accepted the fact some dma chips were duds but now realise its down to bus noise.....

Anyway i followed the guide in replacing the psu....... I should have bought a new switch but luckily mine was in good nick and the transplant went fairly smoothly....... I did cut windows in the plastic shielding between the psu and baseplate for the to-220 style units to sit flush......The hardest part was actually mounting the psu as the holes were quite a way different, This is the problem with atari using a pressed profile for the mount......

I resoldered the switch and power connector to the new psu and fired it up on the bench hooked up to my meter, as i didnt (and still dont) have load resistors i measured the voltage it looked fine so reassembled the STE and it worked without issue.....

By this time i thought that i would mod an STE and a STFM for general gaming (I had been using hatari mostly for a bit of captive) So i orderd some more bits for the STE , A TOS 1.62/2.06 switcher and 32mhz booster, After all this STE hadnt cost much and i was mainly after the ultrasatan so i wasnt too bothered if i blew the arsehole out of it........

The Booster and tos switcher arrived and i once again stripped down the STE to the bare board (What a P.I.T.A. that is.....) and noticed i had 2 soldered in OTP Roms...... I solder sucked the underside of the pins but they refused to come out whole so i clipped those bad boys, assemble and fitted the tos switcher and fired up the board to test..... All working well.

The switcher had to wait till the next weeked (Just gone as i type this) As i had enough of freezing my tits off in the garage soldering, So i assembled the booster easily and my 74f257 chip had arrived (I had a S version in a socket).

I attempted to desolder the funky 68pin socket nicely as i had also purchased a blitter for the fm but this proved impossible, I sucked out the solder from all the holes , freed up the pins and...... bollox, the socket literally fell apart on me leaving the baseplate on the board.

I removed the rest of the pints and baseplate and cleaned up the holes with wick....... NOT all desolder wicks are created equal, I recently got some "Chem-wick" from the bay which has been superb but some previous stuff i got was analogous to the toilet paper you got in school in the 80s, didnt so much do anything except spread sh!t around..........So if you do have crap wick then try dipping it in liquid flux (I find MG chemicals stuff pretty good).

With the socket removed i soldered in the pins to the booster which took several bites at it as i laid all 8 rows in the st first but i just could mate up the booster to them, thats after cutting a notch from the lower left corner to miss an existing socket......
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I ended up inserting the horizontal 4 rows of pins in to the ST and soldering 1 of each row to hold its position the doing the same with the vertical until all 8 were held in the booster then i soldered the booster side first and flipped over the board to solder the ST side....... quick not is the sil networks on the motherboard will not let the boost sit flat so its best to tack in a pin at the height to just clear the sil on the board (under the new cpu)

Once that was in and done i ran a Kynar wire up to the 74F257 chip and placed it into the socket, Another across to the CE on the tos rom (BE CAREFUL NOT TO OVERSOLDER THIS !!!!!!!!!!!) the soldermask around the CE pin is in fact ground.

I added a dupont angled pin and i jammed another into a ground via and solder that so i could add a switch easily. The machine powered up without issue in both tos and 8/32mhz ...... quick gembench proved this......

My earlier 3d print holding the gotek and reloacting the ports now had 2x 6mm holes drilled for switches and now i can select speed and tos ......

This STE is now done and hopefully will last a long long time.........

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