Hi, thanks for the reply.
So the BFG is set to 50MHz.
Original PSU that has had some capacitors replaced.
There is a sticker on the the board stating it's been recapped.
Kickstart 3.2
That's all a good start. At 50MHz the Rev6 will be quite comfortable and should do 100MHz when everything else is stable. Also do you have any idea what BFG firmware version it is?
It's still worth measuring 5V and cleaning PSU plug and mobo socket.
No floppy or IDE connected. I see some multi coloured horizontal lines appear for a second, then grey for a second then the kickstart screen. If I only connect the board end of the floppy cable or just the floppy power then I get grey. But then even without connecting anything at all, I can turn off and on again a few times and I'll get lock up on grey screen, have waited over two minutes and nothing changes. It's inconsistent, nothing I do replicates it predictably.
That really makes no sense. If you can get a hold of diagrom and run CIA tests that would be a place to start diagnosing the floppy issue.
Do you have another floppy cable to try?
Do you have another floppy drive to try?
Can you measure +5V and +12V at the floppy connector as well?
Any other cards installed while you are testing?
Any cracked solder joints on the bottom of the motherboard on the floppy or power connectors? Don't discount mechanical changes like flexing the board when plugging in cables to change behavior - might be worth trying it on the bench as well if you haven't already.
Also - how long are you waiting between resets? The memory on the BFG is reset proof and there are large caps around - give it a good number of seconds >10 between power off and power on and see if it is still consistently failing to grey screen. You can get weird issues with a quick off/on.
With what you have at the moment if the above doesn't get you any further I think you have a good chance of booting from IDE. Make an image in WinUAE of Vanilla OS 3.2 and see if it boots. From there you can run Amiga Test Kit and check things out a bit more.
The original owner has posted a 3640 card and alternate roms so I'll see if any combination gets a stable setup.
Sounds like the seller has gone above and beyond. It's not unusual for things of this age to go flaky in transit, or after a few power on/offs after being stored.