Amiga 600 Boot Problem

[Pat the Cat]

Yes. There are no expansions, but I did reseat the ROM chip, and also tried a different ROM chip (the one that was in the system was an older version, the one I want to use is a 3.1 ROM). Capacitors all look good, in fact the whole system looks just beautiful for it's age.

Flashing red is usually a sympton of a bad onboard memory chip, as I recall. Certainly some kind of hardware issue with exec not starting up properly... so the processor and ROM are probably good.

If you've opened it up already, try disconnecting the floppy drive at either end - could be that that's up the creek. Same with a hard disk.

I guess in theory a bad keyboard MIGHT do it, but on the A600 the keyboard is just a set of switches on a VERY fiddly cable. Probably no need to unplug it, if a switch is bad, it doesn't stop a boot from happening. So leave that alone, for the time being.

Could also be a loose screw, washer or similar, jammed on the board and causing a short. Unscrew the board from out of the case and check. Be careful, the connectors on the back also have little threaded screw headers that also need to come out to examine the board's backside. You need a hexagonal shaped tool or spanner (wrench over the pond) ideally, but pliers will do the job, they just cause scratches.

EDIT: Oh yeah, ROMs. The 3.1 version has to specifically be for an A600. They are not very swappable between Amigas, as a rule of thumb.

[Pat the Cat]

Just tried booting without the floppy or keyboard plugged in and I get a green screen for about 3 seconds, then it goes to the yellow with flashing red.

Have not yet taken the board completely out of the case to check on screws, washers, etc. Will take that step next. The ROM chip is for the 600. I originally purchased it for a UK 600 I also have.

Oh dear. Don't try turning it on again until you've checked everything over visually for something nasty. Like a burst capacitor, or a little bit of metal causing a short cirtcuit.

http://wiki.classicamiga.com/Amiga_boot_error_code_colours

Could theoretically be the power supply, too, I guess. Check the voltages it's giving out with a multimeter.

But, could be just the old ROM is dead and the new one works fine.

http://www.hardwarebook.info/Amiga_500/600/1200_Power_Supply

[Pat the Cat]

I'd try the new ROM anyway. Take care prising the old one out - small flat bladed screwdriver is good enough, make sure you get the notch the right way around. You have to do each end, in turn, a bit at a time. Don't lever it out all the way at once, the pins get bent all ways.

If the old ROM is corrupted and isn't carrying out boot properly, that would also explain the behaviour, to a certain extent. Unikely, but worth a try with the new one. ROM chips are pretty robust, as components go. But when the PROM type are dead, they're dead, AFAIK.

...Could also be a CIA fault, both 8520s live on  the CPU data bus and people plugging stupid things into the Centronics  port can often damge U7, which can then proceed to mess up the data bus  and cause similar symptoms as described here.

Gold dust knowledge, thanks.

It's  a bi-directional port but it's very limited compared to where parallel  ports went. I never knew the data bus could be damaged by silly connections but  it's very easy to plug the wrong thing in there.

[Pat the Cat]

The ROM makes no difference. The result is the same with either one. How would one go about replacing U16 and 17? These appear to be soldered directly to the board. Also, where would I obtain these replacement parts? I imagine I'd have to order them from somewhere on the other side of the pond since I'm in the US?

Pretty much everything on the A600 is soldered apart from the ROM. ROHS standards came in 1992. Lead free solder, so count your blessings that fixing it isn't going to cause health damage.

Spare parts you are looking for are an 8520 (CIA, Complex Interface Adaptor) in PLCC or is it FPGA form (? square SMD) for U7, and if that doesn't work, the RAM chip or Chips. I don't know that off the top of my head, but it's written on the chips.

You may or may not be able to get spare parts. From anywhere. But, they're generally to be had, if you look hard enough and are patient.

As for the soldering skills, if you don't have, find someone local that does. Makerspace or Hackerspace close to you? Fablab, anything like that? Worth a search engine check on your location.

Solder containing lead is now pretty rare, but still available. No more is going to be produced though - at least, not in the USA, Europe, or Japan.I think China has severely restricted the use of lead, but the Chinese economy is so huge, it's very difficult to be sure that environmental monitoring is checking up on that, as far as solder goes.

[Pat the Cat]

...These machines were all built with standard 60/40 tin/lead solder.  Though unless you mistake it for a pork chop and start eating it, or go huffing the lead fumes for years, a one-off repair job such as this is very unlikely to pose a health issue.

That could be why some people with access to tools and have skills are leery about doing the work?

But thanks, always seemed to need higher temp to me. Less tolerant than lead solder.

Guess I didn't take an iron to an SMD Amiga that often. Didn't need to.

But then, I was taught to be careful when connecting and disconnecting things.