surdo wrote:From the photos above, to me at least, the power supply does not seem to be modified and lacks an earth.
I'm really disappointed that your pictures have been posted for so many days and none of the smart guys on the forum have pointed out the obvious problem. It jumped right out at me as soon as I saw your first interior shot, internals1.jpg:
I don't agree that your power supply wiring is original. I'm thinking that it has to have been modified. If it hasn't been modified, and that's the original wiring, then I'd recommend that everyone inspect their Sunfire amps to see if they have the same problem. If they do, then the amps were mis-wired at the factory. (I find that hard to believe, no amps wired like this would have passed CE certification.)
Your amp is wired so that the fuse is on the neutral wire instead of the hot wire. That causes two problems:
1) Electrocution Risk
2) Fire Risk, as in burn your house down
1) Electrocution Risk.
All fused devices are required to have the fuse placed in the hot (black) wire for safety. With the fuse in the hot side of the supply, if there's ever a short that takes place that causes the power to go to the chassis, or to any other destination that's not the neutral wire, then the current through the amp will surge and the fuse is supposed to pop. With the fuse placed in the negative limb of the AC supply, an electrocution type of incident will never allow the fuse to pop. Instead of having a 5-amp fuse in the device pop, you'll be relying upon a high current (normally 15 amp or 20 amp) breaker to open in order to stop the current. Someone is likely to be be dead long before that happens. The reality is that the fuse isn't in your amp in order to prevent you from electrocution. Good wiring with a grounded chassis and a GFCI is the best way to prevent being electrocuted by a malfunctioning Class 1 device.
2) Fire Risk.
Fuses need to be in the hot (black) limb of the supply mains. They are never to be located in the white (neutral) limb. If there is some problem that should develop where your amp develops a short circuit, the wiring is supposed to be designed so that the current passes out of the amp to earth via a dedicated ground wire that is thick enough to be rated for the full current carrying capacity of the device. Notice that your amp doesn't have any such ground wire. As a result, if the chassis goes hot, then current will no longer pass out through the neutral (white) wire and it will not pop your fuse. Since it doesn't have a ground wire, the electricity will find any way out that it can.
When that happens, all of the current is going to exit through any available low resistance path to ground. Since you don't have a ground wire, the only path out of a hot chassis will be via the interconnects. Hopefully one of your other components is grounded, so that the electricity won't pass into a user who happens to touch the hot chassis. The problem, though, is that an interconnet isn't an adequate ground path. It's not rated to carry the full current of an unfused hot mains supply. At this point, the only thing standing between you and a fire is a GFCI (if you have one on the amp) and your circuit breaker in the mains panel. But long before the circuit breaker would trip, that little interconnect would burst into flames, and when the wire insulation bursts into flames, you've got a house fire.
Fuses are supposed to be installed on the hot side of the mains supply in order to prevent house fires. Your amp has a fuse in the neutral side of the mains supply, which renders the fuse worthless.
If that were my amp, I'd re-wire the supply mains to get rid of the neutral fuse, and I'd move the fuse to the hot side of the line. You need to do this right now. While you're at it, I'd add a grounded line. Granted the ground wire may not help you until you move to an apartment with grounded outlets, but you can use an adapter between now and then.
Also, what's up with that transistor that's got the heatsink compound dribbled over it? It looks like somebody who didn't know what he was doing was working on that part of the amp. I'd check that out too.