exxos's Atari, Amiga & retro forum

rabidgerry wrote: 30 Jan 2026 10:49 It looks like there is something in what you guy's are saying @PhilC and @rubber_jonnie .

So baring in mind I am not a skilled guy who knows the specifics about electronics etc. But I've some basic understanding.

Hear goes. So in the photo, I have worked out the soldered hole that has the 3 different coloured lines coming out of it is the negative/gnd for the fan header. So establishing that, I used my multi-meter to test the next component inline with it which is the little black resistor/cap (not sure which) you see to the right of the soldered hole.

So from the negative fan hole to the black component on the right, the yellow line represents a good continuity between it and point 3 from the multi-meter. The pink line represents a little bit of continuity between it and point 2, not great. Then the red line, no continuity at all between the fan negative and point 1. So then I worked out that there is good continuity between point 1 and other gnd's such as the ground on the jtag header.

So this must be negative/gnd in which case as you gents suggest the fan header gnd isn't connecting so well to that little black component which seems to be a gnd.

Do I need to try and solder better points 1 and 2 to the little black component? Thank you for any guidance and apologies for my basic and lack of knowledge.

rubber_jonnie wrote: 30 Jan 2026 11:15
So that 3 legged SMD component looks like it might be a Mosfet, though I'm not 100% sure and it might be there to drive the fan. Before you go and do any soldering use your multimeter to check from the top of the pin to the pad, or if yo can somewhere on a nearby trace that connects to it to be 100% sure that connectivity is there. Simply testing for continuity like that may well give odd results if you're trying to do it a cross a transistor/mosfet.

rabidgerry wrote: 02 Feb 2026 11:55

rubber_jonnie wrote: 30 Jan 2026 11:15
So that 3 legged SMD component looks like it might be a Mosfet, though I'm not 100% sure and it might be there to drive the fan. Before you go and do any soldering use your multimeter to check from the top of the pin to the pad, or if yo can somewhere on a nearby trace that connects to it to be 100% sure that connectivity is there. Simply testing for continuity like that may well give odd results if you're trying to do it a cross a transistor/mosfet.

So there isn't actually a pin soldered in there at the moment. I just was lazy and didn't suck the solder out. Do you think I should try and solder a bit more at that mosfet? The solder currently in the hole connects perfectly to the trace which leads to the first pad on the right that connects to the mosfet.

rabidgerry wrote: 05 Feb 2026 13:07 Can anyone else confirm what they get of the rail?

I realise it's perhaps unconventional and I'm fully responsible for busting my TF1260, but I tried this (see pic) and I get 12v no problem and any fan I tried work as you would expect. Is the transistor a necessary requirement? I have seen some picture of TF1260 cards that do not have it.

terriblefire wrote: 06 Feb 2026 12:07 Question i have is why not use the floppy connector or something if you want 12V all the time. its much better to use that than drawing too much on 12v from the cpu connector. its possibly you've got a resistance/voltage drop at the cpu connector too