More power for a 1200 (and 4K)

[Karlos]

Before getting a  tower, I used an old PC supply.
I was worried about the current levels that would pass through the standard A1200 power socket, so I fitted an additional one.
I used a standard male hard disk power connector (from maplins), fitted into the back of my A1200, having cut a wee hole with a hacksaw and used a bit of super glue. I then powered the floppy disk/hard disk from this socket, and later added an additional feed to the mainboard via the original floppy power connector (be careful of the pin arrangement else you'll pump 12VDC into the 5VDC line!)
The upshot was that I had 2 power leads going into my A1200, both of which needed to be pugged in else it wouldn't work ;-)
This worked perfectly as a temporary fix until I got a tower.

[Karlos]

whabang wrote:
I've heard that one could feed extra power into the A1200 mobo by using the floppy connector.
Is this true? It sounds a little bit dangerous...

Sure. I do that in my tower too. As long as your careful about not mixing up the lines.

In fact, if you have a greedy accelerator, ram, gfx card etc. (ie BlizzardPPC/BVisionPPC) its a must ;-)

[Karlos]

xaccrocheur wrote:

Sounds fine, that's what I envisioned in the 1st place. On the other hand GreggBz's solution is much more elegant : That way you only have 1 cable.

thanks for the options !

Well, as I thought I said the point of having two cables was to alleviate the current levels flowing through the standard A1200 power socket - I didn't want to overload the regulators on there (which happened to an older mainboard of mine).
Better to be safe than sorry. Also, since I used a spare A1200 power cable (from an old PSU) it didnt look untidy, it was just another cable into the back of the machine.

[Karlos]

whabang wrote:
So in theory, I could connect an AT PSU to the miggy via the floppy connector?

You could, but I wouldnt reccomend it as a sole power feed. For example, you wouldn't get -12VDC in which case your sound would be screwed up and your serial port probably wont work properly. The 5VDC and 12VDC lines are the most loaded, esp 5V when you add a few extra tens of millions of transistors in the form of a bigger processor, more memory, gfx card, etc. etc.

If you want to jam the juice in, use both. Also (obviously) power all your drives / fans straight from the PSU.

[Karlos]

whabang wrote:
@Karlos
Conclusion: I don't think that ol PSU of mine is enought to power accelerator, HD, floppy, mobo...

What do you have? It's not a standard C= PSU is it?

[Karlos]

whabang wrote:
BTW. Do the different revisions of A1200 motherboards have a different power usage?

Possibly, but they all use the same voltages which is the important issue. The thing is, any piece of electrical hardware will only draw the power it requires irrespective of how much the PSU can deliver. It's when the hardware needs to draw more power (ie higher current) than the PSU can deliver that you get problems.

Basically you can end up getting voltage drops (so drawing too much current from the 5V line can pull the voltage down) so that the hardware becomes unreliable. Worse still, the PSU can burn out and take the hardware with it :-o

Anyway, bear in mind that the mainboard voltage regulators  have a max current rating before they start to fry which is why I strongly advise a dual power input to the A1200 mainboard.

I know because this actually happened to me once when I had a dsektop 1200 using just the standard power connector with a 200W supply :-(

Luckily, I had an electrical engineer flat mate at the time who replaced the surface mount regs (in the lab at his workplace) so I got away with it ;-)