Amiga 600 guru meditation on boot (sometimes)

[gooddwarf]

Hi everyone!

I'm a newbie to the amiga world; I just recently got my hands on an amiga 600, and I have a little problem. Or better, sometimes I have a little problem, and I hope you can give me some clue on what to look for.

The fact is that sometimes (let's say more or less 3 out of 4 times) it boots up normally (at least to the kickstart [the purple screen with the floppy, forgive me if I use wrong terms], but I got it to load workbench 2.05 the first times before I opened it), but at seeming random times during the boot phase I get a guru meditation, with varying error codes (e.g. 8100 0008, 8100 0000,  8000 0004, 8000 0000, 8000 0003), but always in the same task (000026D0). If I press the left mouse button, then it boots ok.

This behaviour happens also with nothing but the motherboard connected.

Oh, and another detail (that might or might not help, I really don't know): occasionally (say... it happened like 4-5 times in about 50 tries, and just once after I reseated the rom chip) the kickstart screen has some messed up colors, with a lot of gray in the zone of the amiga logo and the floppy.

Actually, when I opened it up to check for visible damage, I noticed that a ceramic smd capacitor near the RAM chip (C17B) failed short (and in fact, burnt a hole in the plastic shield below it), so I removed it (I think it is not essential), but to no avail. Everything else looks fine on the board: I checked the traces near the burnt capacitor and everything seems ok.

I'm a newbie to the amiga world, so I really don't know what to do now. As a side note, I haven't recapped it yet, since I really have no idea if that may be the cause of the problemr. I just don't like the fact that sometimes my A600 doesn't boot at totally random times for unknown reasons, and I would like to fix it if it is possible (before doing other things with it, like cleaning it really well, retrobrighting, installing an hdd...).

I really hope someone can give me some hints on what to look next, I'd really like to solve this issue.

I posted it in this section becouse I suspect it is a hardware issue, since it happens with literally nothing else connected by the pcb (and no software loaded). I hope it is the correct one

[jltursan]

Welcome aboard!

Hard to tell; but given that the motherboard has suffered some damage due, probably, a bad cap and the fact all A600 & A1200 motherboards always need (and I mean always) a full recap I would seriously think about doing that as soon as possible.

Does the SMD caps contacts look dull or even slightly green?, it's something to look for (although a bad cap could look shiny anyway)

[paul1981]

I short circuit is bad news, so you might be wise to download the A600 System Schematics and see if you can find where the C17b connects to to locate further damaged components. Also, as already mentioned, there must be quite a few Amiga's out there that have problematic SMD caps (if they don't now, they will do eventually). Look out for dulled solder joints on each cap or worse still - green joints/blemishes indicative of a more heavy leakage.
AmigaKit might be able to repair it for you, or if purchased with PayPal you could get a full refund if the Amiga was found to be faulty after being advertised as working. Of course, always contact the seller first to sort out problems like this.

[gooddwarf]

Thanks for the replies! I'll probably recap the whole thing as soon as possible (since it also has a really really faint audio) and see if that makes a difference. I haven't already done that because the machine most of the time works just fine, and moreover the caps are visually ok.

I also inspected the location near the C17B. Traces are ok. That cap was a decoupling capacitor for the U17 (which should be a ram chip I think). I have no idea how to test the ram is working, but traces around that chip are ok and there are no shorts... or at least I haven't noticed anything wrong inspecting it

[paul1981]

I've looked into it, it's a 0.33UF which has probably just failed of its own accord (or bending of the motherboard can cause these ceramics to go short). It is a RAM chip - half of your on-board 'Chip RAM' (512K). Try running a memory test program such as: http://m68k.aminet.net/package/util/misc/MemCheckBH

There are lots of other testers available, so take your pick. You should really think about replacing that capacitor though as it is there for a reason - stability.

[gooddwarf]

I'm sorry for the stupid question, but I'm really a newbie with amigas... how can I make the test program you linked run on the amiga?

Unfortunately replacing the C17B will prove almost impossible, since the pads basically exploded with the capacitor and there is nothing to solder to there. Moreover I don't have any ceramic capacitor lying around. The most I can do would be installing an electrolytic capacitor in its place (by this I mean simply between the first and the last pin of U17), but I don't really think if it worth the trouble (and risk).


Update: I recapped the machine, no noticable difference (even the audio is still very faint). Most capacitors were not really bad. I noticed a few traces under C303 (in particular D15) that were almost black. They tested ok with the multimeter, but I might consider using wire there. The same for a trace just under C334 (near the rca jacks for audio)

[scuzzb494]

Hi

I wasn't going to say anything but I guess I might as well. By your own admission you accept you are a newcomer and yet you took your Amiga and started taking it apart and even pulling the ROM chip without first establishing the problem. Here are some tips....

Be very very cautious of advice that starts with the words recap the board. I have 124 Amigas and not one has been recapped. I am not saying that recapping isn't essential I am just saying stop first and establish what is the problem. These computers are old and each time you take the thing apart you risk breaking something.

First thing to do is record everything ' without messing '. Its your property so do as you want. All I want is to save Amigas. So photograph the case, the serial number, the ports. Count the pins and make sure all the various components are where they should be. Check online.. you can check my website there are loads of reference images.

Do some research. LEAVE THE COMPUTER ALONE... until you have all that you need. Check documentation, error codes, other posts on similar problems.

If you are now comfortable to look inside. Make sure you have prepared the work area. Slowly open up the Amiga and look after the screws. Place facework/keyboard on bubble wrap. Carefully hinge from the back and release the drive light connector. VERY SLOWLY. The back hinge tabs are very delicate and break easily.

Now first question... Does the A600 have shielding or no shielding. Can you see the revision number through the hole in the shielding. Is it 1 or 1.5.

OK now check various guides an taking the Amiga 600 shielding off. And then take photographs of the whole of the board. Before doing anything. Record and make notes. That way you will be able to discuss with others and show how the board was before you started flexing it and maybe have broken it. The issue is likely a bad memory. Also is there any expansion boards on the computer.


http://www.scuzzscink.com/amiga/scuzzblog_january19/scuzzblogdjanuary19_0101.htm

http://www.scuzzscink.com/amiga/scuzzblog_january19/scuzzblogdjanuary19_0102.htm

http://www.scuzzscink.com/amiga/scuzzblog_january19/scuzzblogdjanuary19_0103.htm

Few other tips. Never hot connect while the machine is on. Use the correct power source. Connect the mouse into the correct port. Check for pin damage, port damage... VISUALLY.

If you are going to remove the only chip on the board that can be removed use the correct tool.

I say all this cus you want to save the computer and I want to save the computer.

Sadly just one error and we could have lost the Amiga. And that is very sad.

Sorry.. I don't have enough information. I haven't seen the board.  Always start with very small steps and track your passage. Never go further than is necessary and don't try to fix something that aint broke. These are obvious things. And trust me the capacitor issue is not an issue until you have established what is really wrong. Leave the board in the computer until the last. And do a paper or internet desk study before messing with the one thing you cannot replace. The A600. Your choice. Your computer.

scuzz
http://www.scuzzscink.com/amiga/scuzzblog.htm

[paul1981]

http://www.scuzzscink.com/amiga/scuzzblog_january19/scuzzblogdjanuary19_0101.htm

All A600's came with a hard drive cradle. Take another look at your photo and you'll see the shape of the cradle where dust hadn't landed on the shield for years - it's cleaner and shinier and in the shape of a hard drive cradle. The repair shop obviously removed it and didn't bother to refit it.

As for the hard drive not working - did you check the Kickstart version? 37.299 has no scsi.device in ROM, nor support files for the PCMCIA card slot. Kickstart versions 37.300 and 37.350 do and hence can detect and boot a hard disk. I mention those because they are the only other two Kickstart versions shipped with A600's.

If you do have a suitable Kickstart and it still doesn't detect a hard disk, I wonder if perhaps the board requires the Gayle fix chip and it wasn't fitted with one. As you probably know, there's an early Gayle revision that shipped with some 600's that was buggy or insufficient in some manner and the chip to fix these faults was soldered in right below the Gayle chip in position XU1. Of course, that position is empty on most motherboards as most are fitted with correctly functioning Gayle chips.

[paul1981]

I'm sorry for the stupid question, but I'm really a newbie with amigas... how can I make the test program you linked run on the amiga?

Unfortunately replacing the C17B will prove almost impossible, since the pads basically exploded with the capacitor and there is nothing to solder to there. Moreover I don't have any ceramic capacitor lying around. The most I can do would be installing an electrolytic capacitor in its place (by this I mean simply between the first and the last pin of U17), but I don't really think if it worth the trouble (and risk).


Update: I recapped the machine, no noticable difference (even the audio is still very faint). Most capacitors were not really bad. I noticed a few traces under C303 (in particular D15) that were almost black. They tested ok with the multimeter, but I might consider using wire there. The same for a trace just under C334 (near the rca jacks for audio)

It seems to me that your board has been shorted out, probably on the metal shield. I wonder if someone had trod on it when it was on or something hence pushing the traces through the mylar and onto the shield. If not trod on, then the keyboard heavily banged or similar.

To use that program, you'll need a program called lha first in order to uncompress other files from aminet (similar to zip files):
http://aminet.net/package/util/arc/lha

This is a self extracting archive. It should create an executable called 'lha' which you should copy to your C directory, or in your case just to the Ram Disk (or on a floppy as you have no hard disk presumably).

Then, with your lha archive to hand (memcheckbh.lha on a floppy for example) and a copy of lha in either RAM (Ram Disk) or C, double click on the memcheckbh.lha icon and when the 'execute a command' requester opens, insert 'lha x ' before the archive, so that the text box will read 'lha x memcheckbh.lha' without the quotes and press return. Lha will then extract the archive into the same path as the archive itself (floppy in your case).

[generic]                  250     740  33.8% -lh5- 38b1 Jan 29  1995 MemCheck.info
[generic]                 1675    2984  56.1% -lh5- 465a Oct 15  1994 MemCheck/MemCheck
[generic]                 1833    3700  49.5% -lh5- 99e3 Oct 15  1994 MemCheck/MemCheck.doc
[generic]                  310     643  48.2% -lh5- 01cf Dec  8  1994 MemCheck/MemCheck.doc.info
[generic]                  494     884  55.9% -lh5- 8c23 Dec  7  1994 MemCheck/Product-Info

Five files should extract as above (you'll only see four though on the Workbench screen as one is a hidden '.info' file (an icon image). To read the documentation you can boot your Workbench disk, look in the Utilities drawer and run the program called More. Then when the file requester pops up, point it to the text file on your floppy DF0:MemCheck.doc.
The docs should tell you how to run the program and what options (if any) are required.

Just double clicking MemCheck and pressing OK or return should at least give you the options to run the program, or with a bit of luck it will run without options and start a memory test.

To do any of this you will need some way of getting the files from aminet to your Amiga. If you don't have a PC with a floppy drive and a copy of CrossDOS or fat95 on the Amiga side, you'll need a Serial or Parallel cable to transfer files (normally serial). There are kits you can buy with cable and software included. Alternatively, did your A600 come with any software at all? Normally they do come with some Magazine coverdisks or pd software and they will have lha already on them in the C directory. Also, if you're lucky you may find a memory check program too!

[F0LLETT]

Another reason for random guru on boot, is dirty contacts between ROM legs and ROM Socket.