exxos's Atari, Amiga & retro forum

Check the archives for what is needed of the PSU in the MegaSTe.

Meanwell does some nice PSU. The RQ65 for example can maybe work. Got -12V and -5V. It seems in specs. Input 115V or 230V. Should fit nicely.

Thanks DoG might do that.. I picked these up for $10 ea.. and they work fine for other projects.. but if I could use it here would be great..

ANYWAY..

This is the part of the schematic I am interested in. .. But why is the Fan in the -12v area??

If I built a small board that has a 7905 on it.. with the large lead in cap and the following stabilizing cap.. should I not just be able to grab from the -12v output and that will give me my -5v??

James

Specs linked by DoG tell max. load on -12V is 0,3A - so better not pull 750mA from that.
I wonder about the spec. min. load of 0,2A on +12V, as the normally attached fan Nidec BETA SL takes only 150mA. The fan should protect the PSU from being damaged by too less load.

ari.tao wrote: 12 Dec 2019 08:54 Specs linked by DoG tell max. load on -12V is 0,3A - so better not pull 750mA from that.
I wonder about the spec. min. load of 0,2A on +12V, as the normally attached fan Nidec BETA SL takes only 150mA. The fan should protect the PSU from being damaged by too less load.

12V @ 0.3A is 4 watts.
5V @ 0.72A is 4 watts. (So, ok, with conversion loss you're probably looking at 0.7A max.)

terriblefire wrote: 11 Dec 2019 22:41 NIce...

Here is more info on the Ian Stedman stuff... including a github link with all his schematics.

http://www.ianstedman.co.uk/Amiga/desig ... aptor.html

I distinctly remember creating -5V from 5V with a 7905.

I can vouch for Stedy's adapter. I have it specifically for the -5V and my TT works from it.

So the point of this..

I am adding things to my MegaSTE and to my TT030 .. and I thought.. at what point am I going to deal with issues relating to high draw?

I can recap to my hearts content, but it does not allow more power out. What can I do?

I also have a PAK68/30 for my megaST4 - and the ATX is perfect for that.. as I am going to have to mount the whole thing in a desktop case anyway.. so a nice small ATX 75w psu should be able to power all in that nicely.

So that meanwell RQ65-B - is getting rare it would seem. Also not really much of a boost in power, if not a slight bit less.

Thanks for the link on the Steadman item.. that might be the way to go if I run into problems.. but I guess for now.. build.. see what everything draws and go from there.

James

My approach is always wait until you have an actual problem before solving it.

Just something to think about.

terriblefire wrote: 12 Dec 2019 14:33 My approach is always wait until you have an actual problem before solving it.
Just something to think about.

Well, that´s the difference between brothers Prometheus & Epimetheus. I tend to be a fan of Prometheues (the one who put us on fire).
Did Steadman something like PicoPSU? With Pico you´ll have 12V in and everything out...

Most PicoPSUs are rubbish. The one i got wont even power an Amiga 2000.

The white wire on atx supply is minus 5v same as that Atari supply'

Tom