Thread: Mastero MKIV.5 note

Originally Posted by Juliemac

I built the system and it tested fine. But when I tried on the target system which is a Shuttle 1.8 with 512 mb/ 40GB hd it would not pass POST.
There are 2 main 12v lines to the mother board. One on the main connector and one 4 pins Aux 12v.
Separate these lines to the (2) 12v regulators. Separate it starts fine. Together the current draw appears to much.

Now for the final build!

Julie

The 12V rails doesn't mean to be combine together. If you do, it will die soon.
Use one of the 12V for HD/DVD ROM. The other 12V use for the mobo and P4 Aux connector.

Originally Posted by Juliemac

I built the system and it tested fine.

Very cool! Can you answer my question now?

By the way, what do you mean by "split"? Use separately? Then it's the same thing MatrixPC suggests.

Originally Posted by Juliemac

Together they would not start the PC. It would not even get past post. When I split them it booted and ran well. Even the temp was lower.

As for the short life, would that be the MB or the power supply?

To answer your question, it's the PSU and also could cause your system as well.

When you combine the 2 together, you are running 2 regulator in parallel. In this case, one regulator will output more power than the other (2 same components are not always have equal quality), and will overload and burn.
The 5V rail is also running in parallel, but in this part, the 10uH inductor is used to connect the 2(3) together and reduce the change that one is pushing more than the others. It's not a perfect design, but works cuz one of my Sproggy (Supra) is running over a year without any problem.
Some EE guys can answer more to about running 2 regulator in parallel and this design in particular. I am not EE by trade, but with a little interest in electronic to play around with .

Originally Posted by Juliemac

Ok. Got it fixed. The core voltage of a Duron on a Shuttle MB maxes out at 5.4A with 3.4A nominal, so the single 3.3v regulator is enough.

The 12v section takes greater than 5A to start the system properly so the following fix will work!

1) Remove both 10uh coils from the 3.3v regulator section and jumper it first reg to the output pad.
2) rebuild the serial coils from 12v+ to the 12v+ with the center points flying. Add a 1000uf cap to the center point to ground. Attach the yellow 12v line from the ATX and the other 2 lines from the P4 supplimentary lies to this point.

This allows the Celeron/Duron/Sempron on a Shuttle computer to start successfully every time. Temps are reduced as well.

A bit more sheet metal work, in car wiring and dash work and the system will be ready!

Thanks all for all your help.

Can you sketch of what you did?
It may help other people better than just text description.