ACA500+ - AUX port CF card initialization problems

Quote from Jens

It might be worth a try using a different power supply.

Actually, I do own a second Amiga and it does have its own PSU. It's also an original PSU, but a different model.

I tried it out, and poof - the problem is gone! It looks like the PSU is the cause. It took me a while to respond because I wanted to be sure first and made multiple power-off/power-on attempts with time intervals, and so far I didn't have the case where the computer wouldn't boot.

So, the two PSUs are:

• OK: Commodore A-300 Power Supply, 3.0A/5V / 500mA/12V / 500mA/-12V / T 2A
• NOT OK: Commodore A-500 Power Supply 4.5A/5V / 1A/12V / 100mA/-12V / T 1A

The NOT OK PSU is the original PSU for this computer (bought together from a friend 20 years ago). The OK one I bought later and separately.

What should I do now? Replace the PSU? Repair it? Who can repair? Is it even broken? Maybe I should just swap the PSUs between the Amigas (the other one is an A1200 with a Blizzard 68030 expansion)?

Quote from Jens

Do you have a friend who owns a CA-PSU?

I don't know any active amigans in my local area. Only folks who like to reminisce how they were breaking joysticks in half 30 years ago. I'd have to ask on the ppa forum if someone has this and lives nearby, but I think it won't be necessary anymore.

Quote from Jens

What speed is the ACA1234, and does the behaviour change if you increase/decrease the speed?

I'm running at 50MHz, but I tried different settings with acatool and to no avail. Even when I down it to 25MHz, the problem still happens.

The 3.0A type is newer, it surely has fewer years of service.

The 4.5A type is one of the best, but also the oldest switch-mode PSU for the Amiga. It is a very simple design that can be repaired by any TV service shop. And yes, I'm aware that there are no TV repair shops any more in the western world, but the profession is still there, and there might be someone in your home town who can exchange a few electrolytic caps: This is what breaks on a switchmode power supply. These electrolytic caps take a lot of ripple and they heat up in the process. At higher temperatures, the electrolyte ages faster, and they lose capacity and increase their "equivalent series resistance". Spare parts should be a few ten cents each, alltogether probably under 15,- EUR shipped to your door.

Even the soldering equipment isn't special, as the circuit board in a power supply is mostly single-sided, and the parts are through-hole, meaning, you can easily swap parts. The tricky part is to re-adjust the PSU, as this needs to happen under load. Here's where the educated service technician comes in: He/She can operate the PSU on an isolating transformer, connect the maxed-out Amiga and adjust the 5V rail so that 5.0V really arrives *inside* the computer (adjusting for the drop in the cable).

Caution: The voltage inside the PSU is high enough to kill you. You should really have this done by educated personnel who knows the required safety precautions.

Well, I could replace the capacitors myself, but the calibration is the tricky part indeed. I'll try to ask around and see if I can find someone who can help me out with this.

Thanks, your help was invaluable.

I got it fixed. I've found a friend who helped me out with recapping and calibration. The caps in the PSU were in poor condition, so it was a good call to replace them.

To gather more info before the repair I measured the voltage across the +5V and GND in ACA500's clockport. Before the repair the voltmeter would say 4.88V with all components attached and 4.93V when ACA1234 was removed. The other, good PSU would measure 4.91V with all components. I guess this 0.03V difference made the difference. Now, after the repairs, the previously faulty PSU measures 5.02V. And it works - the boot problem is gone.

Again, thanks for the help, and I'm happy that the matter was resolved successfully.

I am having this issue also - I just received ACA this week.

I am using a Checkmate case with the new PSU. Any thought on what to do?

Quote from MWinders

Any thought on what to do?

Remove the known-bad parts and replace them with known-good ones: The Checkmate stuff and the PSU that most likely doesn't have 5V as it's main regulation rail.