SG330 Boot loop - Hardware Issue Debug

Hi Community,

I thought I'll try my luck here, maybe someone can help. I've been using UTM/SG products in small and large variants professionally and also in my private setup for some time, but this is a private (non support) question.

I recently got a SG330 rev. 1 (aftermarket) which I wanted to use for training/test usage. The hardware looks ok, but when I turn the SG on this happens:

• E8/E9 (SFP ports) LEDs go on shortly
• Power LED goes on
• HDD LED goes on shortly
• LCD shows "Sophos Protection"
• 3 beeps - short break - 3 beeps
• reboots (seems to)

No signal on the console or on the VGA output, no response to keyboard interaction..

I do not like to waste hardware so I'm trying to get that thing back to life and figuring out what those 3 - 3 beeps could mean. I figured AMI POST codes it could be memory or keyboard controller (Gate A20 error).
Of course I opened the box, checked RAM (good), replaced RAM, disconnected expansions (FlexPort and internal)

Now I'm wondering if anyone has an idea what those beeps could mean or if there is any other means of debugging this thing? (e.g. I noticed that there is a "Debug Port" on the mainboard, could that be used to get more info?)

Thanks a lot for any hints!