Wizztonics TOS206 upgrade issue - SOLVED

[exxos]

What about under the CPU? I would suggest removing the addon board and just try with basic CPU first.

[PhilC]

In your picture 232209 it's hard to tell but one of the pins on the left hand side is dark. This could be a corroded pin or track. I'd remove all of the solder on that pad, clean the pin and solder pad / track up and then resolder it.

The 244 and 373 can be tested in situ but this would involve needing that scope I mentioned earlier but also requires an understanding of how these chips work.

So, is it sensible to ask if you have the relevant skills to fix this or should you ask someone else? No insult intended, I just remember what a mess I've made of some of my early attempts at repairing things with too little knowledge and incorrect tools. But of course if you are using this as a learning aid then good luck

[Bikerbob]

In your picture 232209 it's hard to tell but one of the pins on the left hand side is dark. This could be a corroded pin or track. I'd remove all of the solder on that pad, clean the pin and solder pad / track up and then resolder it.

That actually is a previous repair.. just to the left of the dark pin (resin) is an arrow.. looks like this had be suspected bad in the past.

So, is it sensible to ask if you have the relevant skills to fix this or should you ask someone else? No insult intended, I just remember what a mess I've made of some of my early attempts at repairing things with too little knowledge and incorrect tools. But of course if you are using this as a learning aid then good luck

Well, theres the rub Philc, this is a 2mb mega - I am in Canada, no one around here is an expert on STs.. I am part of a group of retro computer guys.. and I am sure we will keep working on it.. we have a scope, and people who know how to use it I am told I will be taught.

I have no intention of keeping this.. I want to fix it up and pass it along to someone else.. I dont like lying, so I would want to make sure its fixed as best I can do it before passing it along. So posting it somewhere paying $100 or whatever to fix.. I will only get $300(CAN) for a 2mb megaST with a keyboard and a mouse.. maybe $400 if I'm lucky. IF it had a working TOS switcher in it, thats a bit more. I guess with Mega doing the marpet or your upgrade on the mmu exxos is the only way to get it to 4mb eh?

The only thing under the CPU is the 2.06 roms. and of course traces. I could desolder the CPU.. put one back in with a socket. I guess I would put the Blitter patch back on? and try from there.

What does anyone think about my reflow of the shifter and the MMU pins? Cant hurt I guess. might help? Exxos this machine had those IMP chips.. it seems to be an early board.. those chips are working in the other mega now.. should I return the IMP chips to this board???

James

[exxos]

IMP chips generally cause more problems, so the less of them the better I guess.

If you put the CPU back, you don't need the patch to work, you need to read my page on it all.. but for testing I doubt would need it.

https://www.exxosforum.co.uk/atari/last/MEGAST/index.htm

[Bikerbob]

IMP chips generally cause more problems, so the less of them the better I guess.

If you put the CPU back, you don't need the patch to work, you need to read my page on it all.. but for testing I doubt would need it.

https://www.exxosforum.co.uk/atari/last/MEGAST/index.htm

Oh I did read that page.. I thought the end thought was that only the older early boards needed it. This I think?? is an older early board. C100501-001 REV.1.0

James

[PhilC]

Hi James

Happy to hear you have support.

Where that arrow is I would clean up the flux with IPA so you can get a good look at that pin. Then try metering it out from the chip itself to wherever it goes on the circuit board.

But as exxos suggests, bringing the board back to original will aid in the fault finding process as everything will be as the schematic (hopefully) and therefore easier to fix.

If you were in the UK I'd offer to help as I've fixed a number of Megas now.

[Bikerbob]

I was able to get ahold of Steve at Wizztonics.. he knew exactly the problem I was having.

He has sent me DOCs and a pic of the jumper I need to make.. and the machine SHOULD work.. unless there was something else wrong.. OR I have broken it.. in all this stuff

Anyway.. I will post with results.

James

[exxos]

He has sent me DOCs and a pic of the jumper I need to make..

Could you upload or PM the docs and I can put them on the download page

[Smonson]

These (ATARI) are the only machines I am playing with.. can you show me a pic of what you did? I would really prefer to stop scraping the chip each time the puller slips off.... grrrr

Sorry man, I forgot to come back and post that photo.

When the ICs are in their sockets there's not a lot of gap underneath for the puller to grab the chip, so my puller was slipping off. I filed the base of each "hook" down a bit so it's thinner and can get in underneath a bit more firmly like so. Originally, the base of each hook was rounder.

IMG20191117212423.jpg (240.03 KiB) Viewed 4427 times

[Bikerbob]

Thanks for the puller pic.. I will file mine as well.


The T4 error is fixed. I was able to get ahold of Wizztonics. They are very much still in the Atari biz. Steve will not post stuff or have a website of stuff for sale - at least not for now.. but if you need componets or more specifically Falcon stuff.. They have it. He says they still have about 50 of the server rack cases for the Falcon in stock! (shipping will kill ya!!)

Anyway.. here is the attached zip with the PDF docs and a pic and txt file explaining the pic.

Thanks everyone for the ideas and contribution. This was in effect a blitter issue.. The pic is of a jumper - it replaces the little blitter board. Just like every mega does not need the little blitter board.. every mega does not need this jumper.

James