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.

[Boing-ball]

Mother caps should be replaced if they haven’t been for over 30 years. Also are there any Caps on the MKII 060? I have mine replaced on one of my CSPPC accelerator cards.

[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.

[Boing-ball]

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.

I wasn’t sure for the MKII. Have a MKI that has no electrolytic Caps. But the PPC version has 4. Good luck 🤞🏻

[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...

[Castellen]

Doesn't sound like any of the symptoms I'd attribute to capacitor problems, which usually don't happen unless they start leaking and the electrolyte causes corrosion problems; which is rarely an issue in the A3000.

Could be many different causes behind it.  I'd suggest a few measurements when it's powered on and in the 'dead' state to understand where to look next:
1. What's the state of any of the reset lines while the system is 'dead', are they at run state (5V) or is the system being held in reset state (0V)?

2. If the reset lines are in run state, do you see the system trying to run or not?  Easiest way is measure ROM_EN (pin 12 of either ROM) with an oscilloscope and see if there's activity there or not.  That will narrow down if  the CPU is running and there's valid address bus data.

3. Are you getting a valid 50MHz clock (around 4Vp-p) from the oscillator module on the CSmk2?

[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?

[Tumbleweed]

The KEL connectors are hard to find but they do come up on Amibay and ebay. Last lot I saw were here:

https://www.ebay.co.uk/itm/175803563192?hash=item28eeb57cb8:g:r4QAAOSwa8hkpSbL&amdata=enc%3AAQAIAAAAwF1iWacVnsxSbteMHOAfNiDpbqf4kszPA2VJeSlYgQBaT6E7WB8IZaVa9pwUdXG48%2FiMQ6lkhb6vovhg4sRa5RYWksJSYFfEQtQphECSLCWunJgJygcV%2BbBovhwRW7FYDRtTtHnz8fMl0A5JXokscZzTBYGhEyKwYH72Y6RpO2Fxc0DSni%2BUixr3obwMBqxOlEIrG3olm8FyvCE2KiLV2%2BWSAt6IRASuV%2Bbuz5qUpwNDZfvjuo2HOz64tS2hura%2B2A%3D%3D%7Ctkp%3ABk9SR7y12fSWYw

Weed

[Castellen]

Solder joint issues on the KEL connector are rare, but worth checking.  Cleaning the contacts may help.  Visually inspecting contacts to see if any are not aligned and re-forming any misalignments is usually better then attempting to replace the connector.  Replacement connectors are expensive, difficult to find, and it's a major soldering job.

The clue that DiagROM doesn't show the same issue at power on suggests that it's not related to the KEL connector.  If it was the connector at fault, DiagROM would likely present the same issues at power on as the standard ROM does.  I wouldn't be concerned with the fast memory not appearing with DiagROM, I see that fairly often with correctly working machines, suspect there's a few imperfections in DiagROM.

Given the clues that the A3000 is fundamentally running in the 'dead' state, and DiagROM works reliably, then most likely the system is getting hung up somewhere while booting from the standard ROM.  I've seen scsi.device do exactly this when things aren't happy with the SCSI controller or some of the connected SCSI devices, possibly even bus termination.

If you have the capability to program EPROMs, and a null modem cable to connect to another computer's serial port, I can send you a specially modified ROM to diagnose the power on issue, which will definitively show what's actually running and where it's getting hung up.  Contact me by Email (the PM notification Emails from on this site don't appear to work these days).
http://amiga.serveftp.net

[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.

[Castellen]

But what are your thoughts on it just booting fine with the 68030 on board versus having issues with the CSMkII installed?

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.