Belkin 'Y' adapter blew out 2 4000's

[Castellen]

Someone I know locally recently had a similar thing happen.
He bought one of those 5.25" + 3.5" adaptor/splitter power cables from the local PC retailer.
Turns out the 5V and 12V wires on the 3.5" connector were swapped, which wrote off his high density floppy drive.
Cable was unbranded aside from "Made in Taiwan".  Ahhh, the land of superior quality control.

He took it back to the shop, explained his situation and they forked out for a new Amiga HD floppy drive.
I really didn't expect they'd do it, but some places try to go overboard with good customer service.


Your situation seems pretty nasty.  Sounds like it's given 12V to all the 5V logic which would have done a *lot* of damage :-(

[Castellen]

It's not a fault with the original Amiga hardware.  The motherboard has fuses and series limiting resistors already, such as on the DC outputs of mouse, RGB, serial ports.  That's already more than many home computers have.
Fusing won't protect against an overvoltage situation like that.  You'd have to implement a clamp/crowbar circuit which adds more cost and complexity to the design.

If there has been 12V applied to the 5V rail, it's not an easy fix.  Most of the semiconductors on the board are 5V only.  If the components don't fail instantly, they can fail prematurely in the future.
Short of replacing all the 5V logic (nearly every IC on the board) you can't guarantee a repaired board would keep going for any length of time.  No harm in trying though.
I'd be very hesitant to approach such a job myself, JJ would probably be the same.