Denial

I've got a C128D (not DCR) that went bang last time I tried it, after running for about half an hour, tripping my main fuse at the same time.

From some research, it is either likely to be the inline power filter, or some capacitor in the PSU has shorted. Frustratingly there is no visual (or sniff) cue for what might have failed, so I'm just guessing.

It occurred to me I might be able to use a replacement PSU for a C128, by modifying the board of the 128D to add the square DIN port. I don't actually want the 1571, as it barely worked at any time I've had it, and don't want to use 5.25 disks anyway, so I wouldn't need 12V, just 5v at 2.5 Amps and 9v AC at 1 Amp.

..or is it easy enough to find an existing PSU that would virtually be a bolt-in replacement? Anyone with experience with this?

I haven't yet had to repair the PSU of my C128D, but I would start to check the diodes of the bridge rectifier and the main switching transistor. They may blow and become short circuit, the circuit is protected by the fuse that blows at its turn.
It's a very common failure mode on such circuits.

Thanks, I'm not too keen on repairing the power supply itself, but actually the circuitry looks fairly accessible compared to some.

More my lack of ability here being the issue, so I thought a drop in replacement might be a safer bet.

Actually it turned out that it was only the inline power filter, so no serious repair work required.. yet!

Glad to learn that it was an easy repair!