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Old 25 May 2018, 20:11   #1
r-giskard-reven
 
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Amiga 600 not booting

Hi All,

I've just rescued my old Amiga systems from the loft and glad to see the A500 boots and works well... no such luck for my A600!!

On boot:
  • Caps Lock light stays on
  • TV shows black screen with faint vertical grey lines

I've tested the RGB to scart cable on my A500 and it works well. One thing I did notice was that the 3.1 rom has fewer pins than the socket (1 row too short). I can't remember if I ever got the ROM working before it went up into the loft and I think I remember the instructions indicating that the lack of pins was OK.

I've tried:
  • Re-seating my kickstart ROM (it's a 3.1 which I bought from AmigaKit a few years ago)
  • Detached my IDE drive
  • Detatched the A601 memory expansion

All have no effect.

I also found a site indication that removing a capacitor may have some effect:
http://eab.abime.net/showthread.php?t=73265

I'd appreciate any suggestions.

Thanks

Last edited by r-giskard-reven; 25 May 2018 at 21:04. Reason: Added link
 
Old 25 May 2018, 20:20   #2
MigaTech
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Do you still have your old 2.0 ROM to try in this A600?

Also check caps for leakage over trace lines. Usually shows discolouring around the base of capacitors.

Another point to mention is the PSU, check it is OK and giving good power, if not try using your Amiga 500 PSU to power the A600.
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Old 25 May 2018, 20:23   #3
r-giskard-reven
 
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Hi MihaTech,

Thanks for the suggestions... unfortunately I can't find the 2.0 ROM (I thought I'd never need it again) :-).

I'll check for leaks although a cursors glance revealed nothing. I also forgot to mention that I'd tried both power supplies already with no luck.

Thanks again
 
Old 25 May 2018, 20:41   #4
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Not a problem.

One other thing to mention, your 3.1 ROM if I remember correctly the reason it has extra pins is because, it could be a duel booting ROM. It might have 1.3 and 3.1 on there. Although you had to make a modification to get the 1.3 ROM to boot. Adding a switch to it etc. If it isn't a duel booting ROM, then they must of had a batch of EPROM IC's that allowed 3.1 ROM to be added, but had extra pins.

Anyways, I am sure other EAB members can help with your A600. Knew the A500 would still be kicking!! They are true legends over the later SMT tech.

Keep posting updates, the more information the better the chances of repair success.
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Old 25 May 2018, 21:02   #5
r-giskard-reven
 
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Hey,

Great info. I've checked the capacitors and I cant see any sign of damage... neither are they expanded or showing signs of leakage (i guess that's a good sign at least!)

The 3.1 ROM actually has less pins than the socket, I'm not sure if this was the case for the 2.0 ROM, it was such a long time ago that I replaced it!

The A500 is truly a legend... you can tell the that the quality is different straight away compared to the A600. To start with my 600 won't close cause the floppy drive case clips are busted which I think is a typical issue.

I'm not sure where to go from here. Did you manage to check the google search I mentioned above, I'm curious to see if you think it would be a good idea. The only thing putting me off is that I might damage the board beyond repair.

Thanks again!
 
Old 25 May 2018, 21:05   #6
r-giskard-reven
 
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I've added the link above. Once you've posted at least one message it allows you to add links :-)
 
Old 25 May 2018, 21:14   #7
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Quote:
Originally Posted by r-giskard-reven View Post
I also found a site indication that removing a capacitor may have some effect:
http://eab.abime.net/showthread.php?t=73265
This is worth a try. As you probably know kipper2k is like the Amiga 500, a true legend in the Amiga community!! You can bet that if he has tried this and succeeded, then it is worth a try.

You got nothing to lose as it isn't working anyway and you can always put it back later. Although if you are not confident in removing said cap, let someone else do it for you.
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Old 25 May 2018, 21:39   #8
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A couple of points on capacitors. First, the damage isn't always visible - often it's hidden below the base of the capacitor itself, where the electrolyte can peacefully corrode traces for years before spreading beyond. They don't bulge at the top because they're not designed to in the way the older through-hole types are.

Second, as you may have seen from the Kipper2K post, the A600 is somewhat unique with its reset circuit: it uses the old-style 555-based circuit from the 500 design, but with "modern" surface mount capacitors. This is one of the few occasions where the value of the capacitor really matters as it is used as part of the reset circuit timing, and with age, these capacitors invariably lose capacitance and gain internal resistance to the point where they're no longer really capacitors at all. When that happens, the reset circuit will fail and the machine won't start. This doesn't often happen on the A500 because it uses more reliable capacitors, and it doesn't happen in the other SMT Amigas (1200, 4000, CD32) either because their reset circuit is a different design and not dependent on a capacitor's performance.

This 10uF capacitor would be my first guess based on your symptoms, and seeing it many times before. If your A600 hasn't been recapped already, get *all* of them done as soon as you can (not just the timer circuit one), and hopefully no permanent damage will have been caused.

The missing row of pins on the ROM is ok, the A600 motherboard even includes two arrows to show you where exactly the ROM chip should go. If you wish, you could try the ROM from your A500, provided it isn't modded with small jumper wires as was required for certain A500 models. But my money's on the capacitor.

Edit: Just noticed you're in Scotland. If you're near Glasgow, I'd be happy to take a look for you at some stage if you need help diagnosing it.
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Old 25 May 2018, 22:59   #9
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Quote:
Originally Posted by Daedalus View Post
Edit: Just noticed you're in Scotland. If you're near Glasgow, I'd be happy to take a look for you at some stage if you need help diagnosing it.
@r-giskard-reven, Take Daedalus up on his offer!! This is one member that really does know his stuff and not just about Amiga computers. I was going to mention his name in an earlier post, but I decided not to on account I didn't want to look like I was discrediting, other members knowledge.

@Daedalus, Excellent post as always, superb advice offered!
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Old 26 May 2018, 15:02   #10
r-giskard-reven
 
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Hi folks,

Thanks for all your help, and I may yet take you up on your offer @Deadalus, I'm about 2 hours out from Glasgow so probably not too much of a stretch :-)

Well I gave it a go and unfortunately no joy :-(

I didn't manage to get the whole capacitor off, only the top part as the plastic base stayed in place. There were two points which popped through the plastic base which i made sure were seperated from each other... I take it this would have the same effect as removing the base as the circuit will not complete? I could try and remove the plastic part but thought you folks would probably have a good idea on the procedure :-)

I'm still not 100% sure that the 3.1 ROM is seated in the socket correctly so I have to keep trying different combinations... I've lined up the right hand side of the rom with the right hand side of the socket, do you happen to know if this is the correct place? I've also tried lining up the left hand side (hope I've not destroyed something by powering on in the wrong possition), but it would be good to know the definitive position so I don't have to keep re-seating it.

I guess the other option is picking up a new motherboard from Amigakit or similar as they have them for £23. The only thing is that I'd love to get this one working as I spent most of my childhood using this model (sentimentally atached to hardware!!). One benefit of the new motherboard is that it'll come with the 2.05 ROM so I can test the 3.1 rom isn't the issue.

Thanks again folks.

Last edited by r-giskard-reven; 26 May 2018 at 15:03. Reason: Added info re: 2.0 roms
 
Old 26 May 2018, 15:52   #11
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Quote:
Originally Posted by r-giskard-reven View Post
I guess the other option is picking up a new motherboard from Amigakit or similar as they have them for £23. One benefit of the new motherboard is that it'll come with the 2.05 ROM so I can test the 3.1 rom isn't the issue.
Although the link you used stated (In Stock) I think you would find that it is an old link and that they no longer offer this item.

Your A600 can easily be repaired and as stated Daedalus is your best bet. The base of the capacitor still attached isn't a problem, as long as the contacts to the solder pads, have been disconnected.

The ROM has a notch at the top and should match the PCB markings. Notice them at the top of the ROM socket. First 2 pin slots are not used with 3.1 ROM. (See the image below for further information.)


I am sure Daedalus shall offer further information in his next post. Keep with it.
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Old 26 May 2018, 21:01   #12
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Most likly the ceramic cap C611 that is shorted due to leakage of the electrolyte close to it.
removing those 2 would make the machine start again (to later replace)
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Old 26 May 2018, 22:59   #13
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Quote:
Originally Posted by r-giskard-reven View Post
Hi folks,

Thanks for all your help, and I may yet take you up on your offer @Deadalus, I'm about 2 hours out from Glasgow so probably not too much of a stretch :-)
Cool

Quote:
I didn't manage to get the whole capacitor off, only the top part as the plastic base stayed in place. There were two points which popped through the plastic base which i made sure were seperated from each other... I take it this would have the same effect as removing the base as the circuit will not complete? I could try and remove the plastic part but thought you folks would probably have a good idea on the procedure :-)
Yep, that would have the same effect as removing the capacitor, though the correct procedure is really to use a desoldering tweezers or hot air station to remove the whole capacitor. Especially if there has been leakage, the pads can be very fragile and are easily ripped off the board by any tugging or twisting of the capacitor. Not the end of the world if that happens, but it leads to longer (and therefore more expensive), and uglier, repairs.

Quote:
I'm still not 100% sure that the 3.1 ROM is seated in the socket correctly so I have to keep trying different combinations... I've lined up the right hand side of the rom with the right hand side of the socket, do you happen to know if this is the correct place?
Yes, this is correct. The left hand side of the ROM will then line up with the two white arrows at the sides of the socket that mark the position.

Quote:
I've also tried lining up the left hand side (hope I've not destroyed something by powering on in the wrong possition), but it would be good to know the definitive position so I don't have to keep re-seating it.
Hmmm... That *might* have damaged the ROM chip, but if it was just a short test, it probably survived.

Quote:
I guess the other option is picking up a new motherboard from Amigakit or similar as they have them for £23. The only thing is that I'd love to get this one working as I spent most of my childhood using this model (sentimentally atached to hardware!!).
£23 is very cheap for an A600 motherboard! I would check the page again however that they actually have it in stock. A lot of products are in their catalogue from the past but haven't been stocked in years, and are unlikely to be stocked again.

Quote:
One benefit of the new motherboard is that it'll come with the 2.05 ROM so I can test the 3.1 rom isn't the issue.
Or call over to me and try any ROM version you like But, as I said, if your A500 has a normal-looking ROM (i.e., no patch wires), you can stick it in the 600 and try it there. I've tried a 1.3 ROM in an A600 myself and it worked.
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