Mega ST4 repairs - help, please

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robfeli007
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Mega ST4 repairs - help, please

Post by robfeli007 »

Trying again as there were a couple things I should have done earlier.

I've got a Mega ST4 that was in a shed for 15 years til I recently cleaned it out. I found that a mouse made its nest inside the Mega, making its way inside through the back slot. I was pretty dismayed after removing the cover to look inside. I've managed to clean it up some but can use some guidance before I try to turn it on. Any suggestions on getting it up to working order in terms of what to use for cleaning, etc? I will be reseating everything and seeing if I can remove the memory board as well as seeing if I have the right 30-pin SIMMs.
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Re: Mega ST4 repairs - help, please

Post by mikro »

Is that a 68030 card with fast ram inside?
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Re: Mega ST4 repairs - help, please

Post by frank.lukas »

SST Board Gadgets by Small
fancy Atari Musik anDA Dance "Agare Hinu Harukana" 1998 ATARI http://www.youtube.com/watch?v=JX10fxb5eYE
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Re: Mega ST4 repairs - help, please

Post by robfeli007 »

Might be. I'm not even sure what it is. It's been so long since I last used it due to various reasons.

On the memory chips, I can read Siemens HYB571000AJ-60. Sounds like a 1M-60ns strip? Google doesn't return anything.

The square black chip is marked KS84C31-33CL, which is a RAM controller according to alldatasheet.com via Google.

I'm not sure what the two gold chips are.
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Re: Mega ST4 repairs - help, please

Post by robfeli007 »

frank.lukas wrote: Tue Dec 15, 2020 6:25 pm SST Board Gadgets by Small
And yep, there it is, the SST Board in all its glory, dangit...

https://www.maedicke.de/atari/galerie/s ... ce/sst.htm
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Re: Mega ST4 repairs - help, please

Post by robfeli007 »

I took a close look at things. I'm seeing more damage than I may be able to repair. I downloaded the repair manual from the Atari document archive at dev-docs.org. Here's what I'm seeing.

- much of the mouse stuff and detritus is between the SST Board and back of main board and an area just under the floppy
- the metal shielding at the bottom between mainboard and bottom of case has rust
- C140 under the front of the floppy drive broke its lead with very little pressure
- one of the floppy's power wire broke a couple inches above the board. Easy fix.
- there's a fine black wire that was chewed in the middle. Might be a somewhat difficult fix.
- the battery backup is two AA batteries in the case, Wiring is good on the mainboard.
- U17 is a square chip held in by wire holddowns
- U5 is an empty square socket. was anything there?
- the cable connectors in back are quite good
- underneath the SST Board was in remarkably good shape, as was underneath the floppy drive
- the floppy ejector just pops out on its own

The SST Board came off fairly easily, connecting to the empty 68000 socket. There was plastic under the board as insulation. The chips are all socketed, as are the two TOS chips, so that's a plus.

- the area where the 68030, 68882, oscillator, and long white "3-column" connector has quite a bit of mouse stuff
- some detritus around the SIMM area

I could try removing the chips one by one, and gently at that to clear out the sockets and the chips. Someone suggested using Branson GP cleaner and use 99% IPA to clean off the rest. Any other suggestions?
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Re: Mega ST4 repairs - help, please

Post by Rustynutt »

Right, spend your time on the SST Board, trash the Mega for another one. That's a really rare piece of history there.
Dal actually has one, maybe check with him for spot checks on the SST.
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Re: Mega ST4 repairs - help, please

Post by robfeli007 »

Rustynutt wrote: Wed Dec 16, 2020 7:49 pm Right, spend your time on the SST Board, trash the Mega for another one. That's a really rare piece of history there.
Dal actually has one, maybe check with him for spot checks on the SST.
I found the SST Board's PDF manual online and went through the things of interest and importance. RTFM, you know. One of the things it says is to get the 68000 socketed. Not all Megas were. That plus remove the 2 or 6 TOS ROMs. I got the feeling I may need to replace the CPU, copro, and maybe other chips.

I do have a Mega ST2, Mega STE, C-Labs Falcon. and maybe an STE. Don't ask how I managed to get my hands on them. After 20 years of not being able to use them for some time, I don't remember. I'll have to look inside them.

You say Dal's on here?
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Re: Mega ST4 repairs - help, please

Post by Rustynutt »

Yes, he's kind of the curator :)
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Re: Mega ST4 repairs - help, please

Post by Rustynutt »

Just looking at the Mega, you're in for a.lot of work to get it up and running. If you have an MST2, just as good to put the SST into.
There are better solutions now, for sure the SST is a legacy card, but pretty damn cool to show off.
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Re: Mega ST4 repairs - help, please

Post by robfeli007 »

Rustynutt wrote: Wed Dec 16, 2020 8:40 pm Just looking at the Mega, you're in for a.lot of work to get it up and running. If you have an MST2, just as good to put the SST into.
There are better solutions now, for sure the SST is a legacy card, but pretty damn cool to show off.
Just did a quick search for Dal on the member list, but don't see him.

I've been out of things for 20 years due to educational and medical stuff that took precedence after a move. Let's see... I could use a bit of a refresher in seeing the newer stuff out there. What would be the equivalent of the SST?

I've got a couple DB-19 to VGA adapters to use with the Megas and Falcon. I think I saw something like a video converter somewhere that allows the three resolutions to be used. Research continues.

Edit: Belay that. I found Dal. Seems I searched wrong considering I'm new to this site.
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Re: Mega ST4 repairs - help, please

Post by Rustynutt »

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Re: Mega ST4 repairs - help, please

Post by mrbombermillzy »

Damn dude!

It looks like those mice have trashed the MST...and maybe the SST board.

Like Rustynutt said, if it was just the MST I would have put a mouse wheel and some cheese in it, returned it to the shed for the mice to enjoy, and called it a day (less pain).

However, Im not sure the SST card will be any good either; the bottom of the card where the SIMMS are look pretty 'sh**ty'... literally!

I cant imagine what years of mouse dung would do to a copper trace on a circuit... or what chemical is best to treat it.

Well, good luck. :shrug:
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Re: Mega ST4 repairs - help, please

Post by TheNameOfTheGame »

I've heard of people putting motherboards in the dishwasher to clean them. This might be a good candidate. :lol:

I hope you can get it working again.
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Re: Mega ST4 repairs - help, please

Post by robfeli007 »

Yep, the MonSTer thread. Been going since maybe 2015. I'll have to hold off getting it if I can til I can see what's working post-shed cleaning.

Fortunately, that was the most severely mouse-trashed device I had, other than an 810 drive and a 410 recorder. All were in totes that had open handholds on either side. Those that survived had those closed handholds on the sides. Fortunately for the mice, they were gone enough to not to endure the wrath of being between my shoe and a hard floor.

But seriously...

I'm still unsure about getting it into my dishwasher. We've got hard water, and it's a little difficult at this time to even find 99% isopropyl alcohol at this time in the middle of a pandemic. I'm wondering if hand sanitizer can work, as I found a version that's 80% alcohol. I got plenty of cotton swabs, though. I can try looking around some.

Just took a closeup with flash. You can see a bit more this time.
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Re: Mega ST4 repairs - help, please

Post by Rustynutt »

For me just too hard to tell. Is it more mold, or what?
Just checked, thought by the look of it, you were in the UK :D
DC isn't a lot different I guess. In Oregon now after living at China Lake 33 years. Still learning the ins and outs of humidity!
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Re: Mega ST4 repairs - help, please

Post by DoG »

Needs cleaning first and then take some close up photos to determine state of board. It's just guesses now.

Hand sanitizers "usually" (?) have some moisterizing in it to help prevent skin of drying out when alcohol has vaporized. If that is the case, I would not use it.
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Re: Mega ST4 repairs - help, please

Post by scsilord »

If you get to a point where you need to figure out where a misisng trace went. I can make detailed pictures of a working board.
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Re: Mega ST4 repairs - help, please

Post by robfeli007 »

Rustynutt, China Lake, near Ridgecrest, California?

scsilord, so far, no traces have been cut or lifted, amazingly enough, considering things.

I spent an hour cleaning what I could of the board and the SIMMs after removal using cotton swabs and 70% isopropyl alcohol. I have a magnifying headset that let me look closer. Mouse droppings looked like boulders yet felt like large grains of sand when picked up.

U22 is an oscillator chip, which according to the SST manual, is part number SG51KT33.333MC. Datasheets360 identifies it as a SG51KH Seiko oscillator 33.3333mhz DIP-4pin. Unfortunately, all four pins were rusted through, leaving the legs in the sockets. I may be able to remove three of them, but maybe not the fourth. Right next to it is U18, NTE74S86, which Datasheets360 says it's a "Quad 2-Input Exclusive-OR Gate." That was pulled without issues. There's four chips marked PALCE16V8H-15PC (ee CMOS (zero-power) 20-pin Universal Programmable Array Logic), two marked GAL16V8A--15LNC and GAL22V10-15LP, also PALs with four DM74AS245N near the 68030 which aren't socketed.

I'm not even sure if the two TOS chips can be removed safely but I'll have to try and carefully.
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Re: Mega ST4 repairs - help, please

Post by Dal »

What a great find! I've just replied to your pm.
STE: Desktopper case, IDE interface, UltraSatan (8GB + 512Mb) + HXC floppy emulator. Plus some STE's/STFM's
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Re: Mega ST4 repairs - help, please

Post by robfeli007 »

Unfortunately, the two TOS chips were unsalvageable due to rust. Several legs came off quite easily in the socket and in my fingers. The 68030 and 68882 chips have one or more pins broken off in their sockets. Some of the other chips may be in the same condition. The two long chips on the Mega board, U27 and U46, suffered the same fate of rusted legs in their sockets. So I'm going to have to declare the whole thing a loss and drop it off at the local e-waste. What are chips U17 and U30?

Thanks everyone for the tips, encouragement, and everything else.
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Re: Mega ST4 repairs - help, please

Post by frank.lukas »

There are a lot of programmed GAL 20V8 or PAL Chips on the Board. When one is faulty the whole Board is useless.
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Re: Mega ST4 repairs - help, please

Post by frank.lukas »

... put it into a picture frame and pin it onto a wall.
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Re: Mega ST4 repairs - help, please

Post by joska »

robfeli007 wrote: Thu Dec 17, 2020 1:58 pmSo I'm going to have to declare the whole thing a loss and drop it off at the local e-waste.
Don't recycle that SST board, even though it's in a very rough shape it's a rare piece of hardware and someone would probably want it. It might even be repairable if you're dedicated.
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Re: Mega ST4 repairs - help, please

Post by robfeli007 »

joska wrote: Thu Dec 17, 2020 2:37 pm
robfeli007 wrote: Thu Dec 17, 2020 1:58 pmSo I'm going to have to declare the whole thing a loss and drop it off at the local e-waste.
Don't recycle that SST board, even though it's in a very rough shape it's a rare piece of hardware and someone would probably want it. It might even be repairable if you're dedicated.
I've put it aside for now. I'm not quite that dedicated.

Now framing and hanging it... That's a thought. Just maybe...
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