ACA500+ Aux CF not working with CF/SD adapter

Hello,

I'm just getting started using my ACA500+ (currently with an ACA1221ec) and I was trying to update the firmware + add ACATool, using a FAT formatted card in the Aux CF port.

For this I'm using a microSD card in a SD adapter in a SD->CF adapter (the red one you find everywhere on eBay etc)
I've verified the whole adapter setup works when plugged on my laptop using a USB CF card reader.

Unfortunately neither the firmware flash tool nor Workbench recognise the card. I think the flash tool actually says there is a CF card inserted but it can't see the update file. The LED stays on while the card is inserted, and after a few seconds the A500's power led starts flickering !

I don't think the Aux port is completely broken because a few hours before that, I managed to copy files between 2 Amiga formatted CF cards in the 2 ports.

Maybe I should mention that the card was FAT-formatted on a Mac using Disk Utility, but I don't think that's a factor because FAT volumes created this way usually work in my Gotek and other embedded devices with no issues.

Something else that I noticed is that I started getting checksum errors on the boot CF card that I had imaged a few hours before.

Any ideas if it's likely to be an incompatibility with the adapter, or something faulty with the ACA500+ ?

Thanks

More info after some testing :

- The flash update tool says it can see a CF card but it's not FAT.

- One symptom I often see is the AUX led is half-bright, and the power Led on the A500 starts flickering a few seconds after inserting the CF card.

- The adapted card sometimes shows as CFAUX:NDOS, sometimes not at all in Workbench.

- It does seem to make a difference whether I hot insert the adapted card in the Aux port, in terms of half-bright-always-on-led or not.

- My Aux port is working with a real CF card (I was able to flash the menu system to the latest version this way)

- The adapted card works in the Boot slot ! I was able to run the WB3.1 installer on it. The installer could see both the adapted card in Boot, and the real CF card in Aux. But if I swap them, it only sees the real card in the Boot slot, never the adapted one in Aux.

So to summarize :
The Aux slot in my ACA500+ doesn't seem to accept CF adapter->SD adapter->microSD card.
That's not the end of the world, but it's a bit annoying because I much prefer to use SD cards to transfer files : I don't have many CF cards, and more importantly I don't have a built-in CF reader in my laptop.

Thank you,
I thought about the PSU as well when I saw the Amiga power LED flicker. It's an original non-recapped one, I'll test with something else.

However I still don't understand why the CF-SD adapter works fine in the boot slot, just not in Aux