Mega STE - Attempting a repair!

[displaced]

Thank you very much indeed - especially for the GAL code. The one whose leg I’ve repaired seems to be doing the job for the moment, but it’d be nice to get a fresh undamaged one at some point.

I’ll pick up a 6881/2 at some point - luckily I’ve already got the GAL for that, but no FPU. I’ll check out the FDD HD situation too - it appears to work fine, but the drive itself does seem to be a DD version. I do have the internal FDD enclosure, so that’s good!

It came with the Atari acsi-to-scsi adapter internally and a honking great big 48MB hard drive that I’ve not yet reconnected, but I’ll have a look at some point.

Definitely will pull all that and go for an internal UltraSatan! Got a Mini on my STFM and it’s been great. Lovely bit of kit, that.

Looks like I’ve got some Mylar repairs to do on the keyboard. I’d instinctively hit Ctrl-Alt-Del to reboot, which the machine ignored. Apparently that’s meant to work on TOS2.06, so it seems some keys aren’t working.

Like you say, plenty to do still, but at least it’s alive!

Can’t believe having a chip rotated 90deg didn’t kill the chip or the machine!

[rubber_jonnie]

@displaced I had a 68882 in my PAK 68/2 and stole it for my MSTE, but managed to get a replacement for under £10 on ebay and it all seems fine.

Nice to have the internal adapters, I don't, but having a Cosmosex externally is more practical since it also gives me a network connection which is amazing.

I would like to get one of the HDD caddies though, as mine simply doesn't have space to put an internal drive because of the internal mouldings.

As for the mylar, I used this stuff and it was perfect: https://www.amazon.co.uk/gp/product/B01 ... UTF8&psc=1.

Just be careful though, the tracks are super hard to expose because it is a mylar sandwich, and the tracks are very easy to damage when you peel it off to make repairs.

I used kapton tape to cover mine up afterwards. Worked a treat.

This may encourage you, I found my CTRL key wasn't working because it's the fire button in Wolfenstein 3D, so if you can get it working again, you can download W3d and play it on your MSTE

[displaced]

Thank you! I’ve ordered that stuff - should arrive Saturday.

I’ve got some MEK-based plastic adhesive coming tomorrow so I can cleanly fix the case breaks. What appears to have happened is that during transit the mass of the hard drive caused it to break away the plastic posts it was screwed to. It then bounced around and cracked the HD lid along one of the grilles, and snapped the outer case cleanly at the back-right corner.

Am very lucky indeed that it didn’t damage the motherboard, SIMMs or SIMM slots!

This MEK stuff looks pretty hardcore, but it apparently makes very clean, very strong repairs. I’ll have a few chances to perfect my technique since I’ll start with gluing the HD caddy screw posts back onto the lid. Not visible on the outside, so a bit more forgiving!

I had a brief peek inside the keyboard today. Am I right in thinking all the little black plastic clips have to be teased away from the metal frame in order to get to the Mylar? That’ll be some real slow and steady work!

Edit: ok - I watched a YT vid on replacing the Mylar, and those clips aren’t as delicate as they look. Phew! Just went back and opened up my keyboard fully. There are no obvious signs of damage, but it is very, very dusty. Also, all the contacts on the Mylar are rather dull and grubby looking.

I’ll give it a decent brush-down at the weekend. Would that carbon pen be useful for livening up the contacts on the Mylar for the problem keys, if it does turn out that the traces are all ok?

[rubber_jonnie]

I don't know if it works on the carbon pads, trouble is it dries quite hard and I'm not sure how well it would last in that scenario.

You should really check out the mylar traces with a strong magnifying glass to be sure there is no trace damage. Tbh I have a digital microscope and needed it to see the finer damage.

If you do find trace damage, make sure you mask off the area you use the pen on as it can be quite globby.

[exxos]

Contact grease can be used on carbon key pcb pads.. Otherwise unless they are broken then don't mess with them. I don't remember if the keys have carbon on them it uses a membrane contact .. But you can get keyboard fix stuff to repair the carbon key pads.. Thing is, don't fix things which are not broke.

[rubber_jonnie]

I have to agree with @exxos about the carbon pads.

Thinking about it, I used a cotton bud soaked in electrolube and dabbed mine very gently, but only those I thought had a problem.

The keys on mine at least have a carbon rubber bridge, and those generally don't seem to fail.

Remember, the carbon paint is thick and you could end up with one pad higher than the other meaning the carbon rubber bridge on the key doesn't bridge correctly.

I'd stick to just fixing the traces with the carbon paint.

[stephen_usher]

The carbon paint stuff Exxos sold was very good, if you mixed it well enough and cleaned the carbon/rubber with IPA first. It did wonders for my TT keyboard, which went from mostly not working to fully working.

But yes, if it ain't broke don't fix it. Those little plastic tabs holding the metal back plate on are fragile and a pain to release. Designed for manufacture and not for maintenance.

[displaced]

Thanks all!

The MEK solvent I ordered arrived today. Just spent a bit of my lunch break fixing the MSTE’s case... this stuff is incredible! Absolutely seamless, strong bond. After I’ve primed and resprayed the case, there’ll be no sign at all of the repair.

Agreed regarding not fiddling with stuff that works. So I took a bit of time trying to figure out what’s going on with the Ctrl key without disassembling again just yet. If I push the key as normal, it doesn’t work. But if I keep it held down and rock it left-to-right, it works. If this was an ST-style keyboard. I’d rub a soft pencil on the black but if the rubber dome. But I’m not sure how to proceed on this TT-style keyboard. I’ll take a very close look at the mylar, but might I also need to check anything on the part under the key that makes the contact when pushed?

Oh, and do you know of a PRG that’s handy for testing keyboards? I’d like to be able to check each key works and that there are no intermittent/dodgy contacts - particularly on modifier keys like Ctrl. If there isn’t, it sounds like an excuse to break out GFA on my ST for the first time in 30 odd years!

[stephen_usher]

Ah, the rocking from side to side gives it away. It's definitely not the mylar, it's the carbon impregnated rubber. I'm pretty sure that the carbon on the surface oxidises and then the surface is non-conductive.

[sporniket]

Oh, and do you know of a PRG that’s handy for testing keyboards? I’d like to be able to check each key works and that there are no intermittent/dodgy contacts - particularly on modifier keys like Ctrl. If there isn’t, it sounds like an excuse to break out GFA on my ST for the first time in 30 odd years!

The diagnostic cartridge embed a keyboard tester. That's how I could assess the list of non working keys on my STE keyboard.