I was playing with some friends last weekend at fairly low volumes and after about 20 minutes my Dizzy 30 made some horrible noises, then went silent, at which point I realised there was smoke coming out of the input jacks and wafting out of the back.  I had recently re-wired the speakers (a Celestion Blue and a G12H30) to be parallel instead of series by having a cable from each of them and using both of the speaker plugs, as according to the schematic these are in parallel.

And yes, I changed the impedance switch to 4 ohms.  I had been playing at home like that for a couple of weeks and everything sounded fine.

I thought that maybe I had misinterpreted the schematic and had blown the output transformer.  I wondered whether it was the whole thing or maybe just the 4 ohm output, so I unplugged one speaker, switched to 8 ohms and turned it back on.  Surprisingly it worked, which was lucky because I had a gig that night, which also went fine, even at medium volumes, although there's been a low level hum that I don't think used to be there.

Meanwhile, during the week some new EF-86 valves I ordered on eBay months ago finally turned up, so I've been swapping them around all week and having fun.

I wanted to see if I could figure out where the hum was coming from.  After eliminating the pre-amp as the source I decided to try swapping some output valves around (I have some JJ's that came with it and some Sovtek EL34Ms which I think sound better, but they all worked fine as far as I could tell.)

After trying a few combinations suddenly there's more bad noises and silence and smoke.  Fearing that the output transformer had gone for good I opened everything up, and the picture is below.  Can't see any scoring anywhere, what seems to be fried are the resistors on the output valves on one side (circled).  I also noticed that there is a brown wire that is lodged between the pins of one of the output valves (arrow on the diagram), and that it looks like the insulation may have melted.

This was built at Ceriatone, not by me, and everything else looks great, but surely that wire's not supposed to be there?  I'm in Australia, what are my options for getting it fixed?

Never mind, looked a bit more closely at the schematic, dual 250K, but log or linear?