Yep, you've guessed it! Fumbling around in the dark and I got the polarity wrong. You never think you are going to be that person, until you are... I've fixed the cause of the issue by upgrading my power supply this morning - stable door after the horse and all that. Rather annoying since I haven't used the kit for a couple of years, and am rekindling my interest following a fascinating day at PAS2023. Anyway, I digress.
It's pretty hard to faultfind the board properly, as i sold my handset years ago, relying on a Lynx Astro cable for communications. Which was fine until it wasn't. ASCOM now rather predicatably has a comms error with the mount.
However, now it's broken, obviously i'm not getting comms with the mount, and the power LED doesn't light up, which from what I've read is a clue. I've stripped down the mount and have the input board and control board on my bench, and I'm tracing the power through the system - I found an old thread where @malc-c went through this same saga - your posts were fascinating and awfully helpful, thank you. In particular, i've inspected the two 470uF capacitors - they look ok, but I'll dig through my spares box and see if I can find some since I've probably got some lying about. I've checked conductivity across all the resistors and inductors, and everything seems fine, so far. Except obviously it isn't!
I've got another board on order, as it's been twenty years since my electronics degree, so i'm not too hopeful, but I'd love to fix this one if I can.
My plan:
Replace the two big capacitors (C41 and C3, by Jumper 1)
See if it works (unlikely!).
Any other likely culprits to hit next? A schematic would be useful if anyone knows where to find one, so I can trace the power through the board until it stops...
Thanks, Jim