Amiga 600 boot problems

[demolition]

Hi all,

I hope someone here will be able to help me out a bit.

I have an Amiga 600 that refuses to boot. When I turn it on, I first get a black screen, then three different shades of gray, and then it just stops there.. A working A600 will show one more lighter shade (white?) before you hear the click from the floppy and the animation is shown.

According to the list at http://www.amicue.org/TechStuff/amigaboot.html it seems to be stuck at '12. Check that software is coming in ok.'. I am not entirely sure what this means though. Which software is this, as the ROM is tested earlier? It never shows any non-gray (error) color.

Caps lock goes off as it should and does not show any error.

What I have tried so far:
Besides a bit of of nasty residue (coffee/coke I guess) and dust mixed well together, the PCB had some corrosion, mainly around the bandpass filters and the IDE connector pins probably due to acid from the caps. I stuck it in the dishwasher, cleaned it up with demineralised water and dried it in the oven on low heat. It came out looking almost like new, although the solder pads around the caps still looked a little dull.

I have then replaced all electrolytic caps as well as checked that they all connect to the rest of circuit where they should. This should all be good.

I have another working A600 and have swapped the ROMs around to check that the ROM is working, which it does.

I have tried booting the main PCB alone without any KB/FDD connected.

After all this, the problem remains and has not changed character in any way. What should my next step be? Although I do have access to hot air rework equipment (and know how to use it), I do not like messing too much with the ICs on my working unit.

Regards, Martin

[kipper2k]

Sounds like one of the CIA chips is toast. They are soldered so you would need to remove and replace. First CIA to check would be the one right next to the Ext floppy drive connector

[demolition]

Thank you for the reply. I think it will take a couple of weeks before I will be able to continue working on it, but then I will take a closer look at it, and maybe also check the pcb connections in that area.

Would it make sense to switch them around or would it still provide the same error, if one of them is faulty?

EDIT: Looking at the schematics, it looks like the amiga should be able to boot without the two 8520 chips, just without working parallel and rs232 ports or am I missing something?

[kipper2k]

Originally Posted by demolition

Thank you for the reply. I think it will take a couple of weeks before I will be able to continue working on it, but then I will take a closer look at it, and maybe also check the pcb connections in that area.

Would it make sense to switch them around or would it still provide the same error, if one of them is faulty?

EDIT: Looking at the schematics, it looks like the amiga should be able to boot without the two 8520 chips, just without working parallel and rs232 ports or am I missing something?

They are both soldered, would be a pain to switch them, I would replace one at a time, and yes, i know the a600 boots without the even CIA

Her's a link showing an A600 booting with the right hand CIA removed. It would freeze on black screen with the bad one in place.

http://eab.abime.net/showpost.php?p=820581&postcount=13

[demolition]

Well, then that will surely be something I have to try then. Looks like it shouldn't be too hard to get it out.

Too bad my calendar is full the next couple of weeks, can't wait to see if it solves the problem. :-)

[demolition]

So I managed to find the time to desolder the CIA chip (U8) and... it works! I now get to the KS start screen.

So does this mean that the 8520 ic is definitely broken or can it still be some of the surrounding components? Maybe I should buy some more broken Amigas just to get some parts.

All PCB tracks look perfect in that area btw.

Edit: Just attached a HDD and it boots up WB just fine. Mouse+audio also worked perfect, unlike my other A600 which had a few problems in that area.

[demolition]

I have managed to get my hands on a 391078-02 (2 MHz) CIA chip. Am I right in assuming that it should also work in the A600, which normally has a -01 (1 MHz) chip?

[kipper2k]

Originally Posted by demolition

So I managed to find the time to desolder the CIA chip (U8) and... it works! I now get to the KS start screen.

So does this mean that the 8520 ic is definitely broken or can it still be some of the surrounding components? Maybe I should buy some more broken Amigas just to get some parts.

All PCB tracks look perfect in that area btw.

Edit: Just attached a HDD and it boots up WB just fine. Mouse+audio also worked perfect, unlike my other A600 which had a few problems in that area.

You should be able to just replace that cia chip with a new one now and it should work.

[demolition]

Originally Posted by kipper2k

You should be able to just replace that cia chip with a new one now and it should work.

Also with a 2 MHz version (from A1200 I guess)? If so, then I'll do that this weekend.

[demolition]

And I managed to solder in that 2MHz CIA chip now, but unfortunately the old error came back. Now it is again stuck on the item 'Checks that the software is being executed.'

Either it doesn't like the 2MHz chip or something else is wrong. I'm thinking maybe U29 could be the culprit?

[lesta_smsc]

Just want to say well done with soldering! It's a tough one that! As for another cause, there are meant to be 2 CIA chips?... Have you tried swapping them around?

[demolition]

Originally Posted by lesta_smsc

Just want to say well done with soldering! It's a tough one that! As for another cause, there are meant to be 2 CIA chips?... Have you tried swapping them around?

Luckily I have access to some decent soldering gear at work, otherwise I wouldn't have tried it.

I doubt that swapping them around will give me any clue as to what is going on. Since it will boot just fine from IDE with the right CIA removed tells me that the left one is good (at least not blocking the booting). And as it now has a new CIA chip on the right side, I'm guessing the error is to be found in another component probably connected to U8.

I hope I will be able to try out some more things tomorrow.

[demolition]

I removed U28 and U29 and no luck - still stuck in the same place. Does anyone know what it actually does at this point ('Checks that the software is being executed.') where my Amiga is stuck? Is it trying to access the floppy drive?

[Arnie]

I have a broken A600 board, you can have the cia chips from that. The board had no video output so I'm not sure whether the chips are working or not but, you are welcome to try them.

[demolition]

Originally Posted by Arnie

I have a broken A600 board, you can have the cia chips from that. The board had no video output so I'm not sure whether the chips are working or not but, you are welcome to try them.

Thank you for the offer, however I already have a new CIA chip from Vesalia which I am certain should be working. I could see that it hadn't been soldered before, although it showed signs of having been in a socket, so I expect that they have tested it that way.

So for now I think that at least two out of the three CIA's I have is working.

Also, on this site I have confirmed that most Amigas incl. the A600 can use both the 1MHz and 2MHz versions:
http://www.amiga-stuff.com/hardware/8520.html

[demolition]

Finally, after desoldering both CIA chips I noticed than one via below U8 had completely disappeared. Since it was gone completely I missed it the last time I desoldered U8. The other vias in the area looked 100%, so it seems a little weird how this one could have gone like that.

I fixed the connection, soldered in both CIA chips, and so far it works, so hopefully another Amiga has been saved from eternal sleep.

It boots perfectly from floppy or HDD, and since I haven't been able to get my ACA620 completely stable in my other A600, I can now test it in this one to see if I can get it to work better.

Edit: I also found another broken via right next to the RGB port (see picture), although I'm don't think it would cause it not to boot.

[prowler]

Congratulations! Well done! Top marks for perseverance.