STE - White Screen resets

[veroli]

Hi all,

so after many months found some time this week to do some Atari refurbs.
Machine in question is 4mb STE. I bought a fast tos switcher from here, installed it, as per the way ive done with a previous,
Gave the machine a clean up and recapped the PSU.
Testing before re-assembly and powering on machine get a white screen and then a reset continually under tos 1.62 and on 2.06 two bombs and some screen corruption.
So far i have tested and re-seated all sims,
swapped in a known good PSU, tried multiple VGA cables and adaptors and monitors.
Swapped back in the original TOS roms.
connected another floppy and disconnected.
tested 7406 u210 pins 2 and 4 with multimeter both reading 5v
machine is as bare bones as it can get it but still exactly the same issue.
I haven't got anything else to reseat so am at a bit of a loss now.
Motherboard is ca 401177
Does anyone have any other suggestions ? feeling frustrated with the amount of time ive spent on this.

any help appreciated
thanks

[exxos]

You will get bombs with 206 if the floppydrive isn't connected.