exxos's Atari, Amiga & retro forum

stephen_usher wrote: 07 Oct 2026 00:02 One thing that puzzles me is if the ground is earth referenced then assuming that the power cable is also earthed then why didn't the socket or even the house RCD trip as soon as it started to conduct?

Good point..

One other finding.. The mains earth wire basically goes nowhere. It looks like the design idea was to feed GND via the mounting bolts to earth to the motherboard.. But the spacers are plastic and theres nothing to make the connection.. I'd have to look more closely but I don't think the scew posts in the case will make any sort of reliable contact to the motherboard GND.

But even so, a short across the mains switch to mains gnd should have blown the rcd.. Saying that.. Our fuse box is old and uses cartridge fuses.. We going to look to upgrading next year.. I'll have to ask the owner about his fuse box..

stephen_usher wrote: 07 Oct 2026 00:02 Not much isolation between the two sides of that switch. One spark and the atmosphere inside the cavity becomes a conductive plasma.

Not my area of expertise but some switches the dielectric is a gas other than air. Presumably this allows the gaps to be smaller? Not saying this is the case here. I didn't read the datasheet

exxos wrote: 06 Oct 2026 23:28 ...and the money shot...



PICT0017.jpgPICT0016.jpg


Can I goto bed now ?

:dizzy:

Well that's pretty definitive, even looks like some of the internal contacts got a bit melty. I can only imagine what the inside of that switch was like at the time it flashed over...

You may go to bed now 😁

Wow, look at the switch internals, that photo makes it pretty clear what happened.

I'm wondering if the mains lead was also fitted with a 13 amp fuse as well. Manufacturers of those power leads rarely fit correctly rated fuses.

Hoping the Falcon isn't just a board full of dead chips now.

PhilC wrote: 07 Oct 2026 09:00 Wow, look at the switch internals, that photo makes it pretty clear what happened.

Despite what's written on the back of the Exxos Forum toilet door, I'm surprisingly un-au fait with exploded and/or melty electrics. I'm not sure what I'm seeing in that photo.

The burn marks around the side I can spot, but inside I'm not sure what I'm expecting to see and therefore what that is or isn't in relation to that. Can you explain a bit?

Just interested to learn but don't know what I don't know there.

BW

Badwolf wrote: 07 Oct 2026 10:34 The burn marks around the side I can spot, but inside I'm not sure what I'm expecting to see and therefore what that is or isn't in relation to that. Can you explain a bit?

The two sets of goldy-looking plates going from left to right are the contacts onto which the rocking pieces of metal (each north-south orientation) pivot on and take their main contact from. You will note that each of these plates is highly pitted in the location where the two sides of the switch are closest. This means that there has been a significant;y large electric arc between the two which has vaporised some of the brass. The plastic separator wall is also blackened in that area with some signs of melting. The vaporised brass has been redeposited around the insides of the switch.

stephen_usher wrote: 07 Oct 2026 11:56 The two sets of goldy-looking plates going from left to right are the contacts onto which the rocking pieces of metal (each north-south orientation) pivot on and take their main contact from. You will note that each of these plates is highly pitted in the location where the two sides of the switch are closest. This means that there has been a significant;y large electric arc between the two which has vaporised some of the brass. The plastic separator wall is also blackened in that area with some signs of melting. The vaporised brass has been redeposited around the insides of the switch.

Cheers,

BW.

I guess if the switch was rocked over rather than snapped over abruptly then it would be more likely to create a spark.

Sometimes a lack of mechanical sympathy can be helpful in using a switch the way the designers expected a typical user to abuse it.

peters wrote: 07 Oct 2026 16:19 I guess if the switch was rocked over rather than snapped over abruptly then it would be more likely to create a spark.

Sometimes a lack of mechanical sympathy can be helpful in using a switch the way the designers expected a typical user to abuse it.

Yeah it's a good point..

The problem with the switch is basically three ways ON - OFF - ON.. So if you push too hard you miss the centre off position.. So you would naturally not push it as hard in order not to skip past the off position..

There was KFC, now there is CFF : Centuriontech Fried Falcon.