Amiga 3000 cold power on issues

[Betelgeuse]

I've got an Amiga 3000 with a 25MHz 030 on it, rev 9 board. Everything works fine with the stock configuration. When using a Cyberstorm MkII with a 50MHz 060 CPU then the Amiga has random cold power on issues. What happens is that when powered on from cold (overnight or several minutes after being off), the power LED remains dim and the screen is black. Leaving this on for a few minutes and then power cycling allows the computer to boot normally and it will continue to do so until it's turned off for a while. My guess is that there is a bad or several bad power capacitors on the board that are not able to provide the voltage the CSMkII needs, but after they had some time to charge up they work fine. PSU voltages seem fine also. Is this a reasonable assumption? Board has not been recapped, but I've ordered caps to do so just in case.

[Betelgeuse]

Thanks. I'll be replacing all the caps this weekend. The CSMkII only has tantalums or ceramic caps, so I think those are fine, no electrolytics on it.

[Betelgeuse]

Well, I recapped the whole board and the riser card just in case. Tested a few caps and they seemed fine. System boots up fine with the on-board 030, but the cold boot issue still persists with the CSMkII, so I'm not sure what is going on. It may be a bit more reliable in terms of booting than before the recap, but I'm not sure. Very annoying...

[Betelgeuse]

Thanks, I'll give it a shot. The CPU is definitely not running based on Caps Lock test. But I'm pretty sure the CSMkII is fine as it works without issues in my A4000. Also, the fact that it works fine after warming up is puzzling. I already took apart the PSU, so I'll replace those caps that I have as maintenance and reflow the solder joints on other things as a precaution. Should have my oscilloscope later this week to do more in-depth troubleshooting.

[Betelgeuse]

Forgot I had DiagROM, put that in and the machine boots fine. Tests seem to pass fine, but FastRAM was not detected on the "dead" state system, despite 4 32MB SIMMs. Perhaps there is an issue with FastRAM on the CSMkII, or does DiagROM not detect memory on the card, cannot see why that would be the case? Otherwise all tests pass.

[Betelgeuse]

Probed around while in dead state and the system is in RUN state, not RESET. There's also activity on the ROMs and the CPU clock is generated properly, so I have no clue what's going on.

[Betelgeuse]

I think I've figured it out. Heating up the FAST slot on the A3000 motherboard makes the system boot up every time, but not the slot on the CSMkII, so it is either the FAST slot or a component in proximity to it. My guess is a bad solder on the slot or the slot itself. I'll probably reflow the connector and see if that fixes it. In case it doesn't, are there any sources for these connectors?

[Betelgeuse]

Thanks Castellan, some very useful info. But of course now the machine is booting fine all the time, so I'm not sure what's going on. I suspect that won't last though.

In terms of the SCSI issue, the system has no problems booting without the CSMkII, it is only with CSMkII and regardless of whether anything is plugged into the SCSI port. I use SCS2SD with it. I do not see termination jumpers installed on the board, just empty sockets for those. Not sure whether that is normal.

Sadly, I do not have a programmer or eraser, so I have no way of writing my own ROMs. But what are your thoughts on it just booting fine with the 68030 on board versus having issues with the CSMkII installed?

[Betelgeuse]

Just as another tidbit of info, BFG9060 boots every time on the A3000, so it's some kind of issue with the combo of A3000 and CSMkII.

[Betelgeuse]

There's not enough information to say exactly what might be causing the problem.  You mentioned that the BFG9060 works reliably, but then you also said that the CSMkII "is now booting fine all the time".  There's obviously some kind of intermittent issue somewhere.

You'd need to collect more clues with the system in the fault state to draw more solid conclusions, which you can't easily do without some diagnostics tools such as a special ROM to see what's happening under normal boot conditions.

Intermittent problems are often caused by issues with connectors, and the A3000 is full of these in the form of horrible IC sockets with tin plated contacts.  In these situations it's often worth removing each of the socketed ICs, including the PLCCs, carefully brushing all contact surfaces with isopropyl alcohol and re-inserting them.  Be sure to use a PLCC extractor tool since anything else will damage the sockets.  Otherwise leave the PLCCs alone and just focus on the DIP devices.

The KEL connectors are at least gold plated, so don't suffer the same tarnishing and oxidisation problems that tin plated contacts do.  They're usually reliable except when individual pins somehow get over-compressed or bent out of alignment.  You can also brush the contacts with isopropyl to remove any surface contamination.

Thanks, sorry wasn't clear. The system was booting fine yesterday with the CSMkII, but not today, which is when I decided to test it with the BFG9060, so it's clearly some issue between the A3000 and CSMkII.

I did remove and resocket all the chips and cleaned them up, so again not that. Why does it work fine after the system has been powered on for a while? That's the puzzle, sme heat-related expansion of a bad solder or something? I'm close to just giving up at this point...

[Betelgeuse]

Have you tried changing the CPU oscillator? Believe it or not, it could be just a simple fix as that….

Yes, and I just received a 50MHz one from DigiKey along with a socket. But I measured the oscillator and it is outputting 50MHz. Weirdly, heating the area in the vicinity of the oscillator with a hairdryer makes the machine boot every single time, but not other areas on the board nor the CSMkII. So maybe it is flaky in a way that is not showing up on an oscilloscope and heating it fixes it? I did reflow all solder joints in that general area but that had no effect.

[Betelgeuse]

Well, it wasn't the crystal, which was a royal pain to remove due to the large ground plane underneath, but at least it's socketed now. It may be one of the resistor arrays, as heating those alone makes the system boot up. Do those fail in this manner?

[Betelgeuse]

An update, heating RP109 makes the system boot. So it may be that component. It connects to the CPU address lines. Maybe the 030 is more tolerant of some fluctuations but the 060 or the added length of connections to the 060 in combination with the CSMkII architecture causes the issue. Will replace it once I get replacement parts and will update here for others who run into the issue.

[Betelgeuse]

I was having similar issues with my A1200.  Wouldn't boot at first startup but would eventually start and run fine.  Tried sorting it out but never did.....untill I pulled out my Blizzard '030 and replaced it with a PiStorm. Any boot issues vanished.  Could be your processor getting old...

Thanks, it is possible something on the CSMkII is causing the issue, but it's not the CPU as I have several and the behaviour is the same with different revs of 68060. I'll replace the resistor pack I'm suspectful of today and we shall see if it makes a difference.

[Betelgeuse]

Well, I've spent the entire weekend on this thing and it's starting to drive me boing! I replaced the oscillator, no change, replaced the 2 resistor packs near the ROMs, no change. The old ones tested OK, which I expected as I've never seen those go bad. BUT, pressing on the ROMs, either one, makes the machine boot, as does heating them. So I replaced those sockets, and it is more reliable but after a long power-off period it still won't boot, pressing on the ROMs quite firmly makes it boot. The sockets are new and connections seem to test out ok, and it always boots with the built-in 68030, so I think those are fine. I looked all around that area and see no issues. But, how many layers is the 9.2 rev A3000 board? Could it be a bad via or a trace in the board that's wonky? So frustrating!