iMac SMPS

[Eva]

OK, the 24V are taken directly from a winding in the flyback transformer as I thought, so they should be employed in an unipolar way.

How do you want to solve that? The slave PSU has to be powered from a flyback-like arrangement. We can either build a new off-line flyback or use a conventional 50/60Hz transformer and then a low voltage switching circuit. In the latter case, the voltage is not very important, it may be something in the 20V range.

[pinkmouse]

And over to the area of the small heatsink:

[pinkmouse]

OK, if we go switching LV, I have a 100VA 12-0-12 that will be around the right voltage, I'm just a little worried about power consumption, though iMacs are fairly efficient.

If you can point me towards a suitable circuit for an off line flyback then I suppose I can reuse the existing HF traffo. The switcher is a 5S12650 (it looks like, very faint printing), so I suppose I could start googling for datasheets to see if I can reuse that as well.

[pinkmouse]

I've found schematics of the PAV board! Unfortunately in French, not my best language, but you can't have everything.

http://www.mactronique.com/files/art/pavdv.pdf

Strange that I couldn't find them whilst searching for iMac schematics, but only on the chip reference...

[jleaman]

Originally posted by pinkmouse
Thanks Jason, but the problem is not with that board, I just need to get high frequency 24V ac into it, normally provided by the huge iMac PVB, (power and video board, but don't let the video bit distract you, it means CRT driver stuff).

Yes i know what all this is. I am daves second hand side kick for fixing all these imac's. Fixed to many of them ..

[planet10]

I've posted this thread to our tech that would be most interested (being a Mac tech is all about board swapping, but at least he can tear down 2 iMacs & make one in record time).

Failure of CRT (analog) boards is the most common failure that relegates the remains of a CRT imac to server cat bed or fishtank housing duty.

If we can get this sorted i have at least 2 (& Anton at least 3) iMac digital boards that could be reserected.

dave

[Eva]

It doesn't seem hard at all to produce a new flyback using only the parts from the old one and a new PCB. I could design that PCB and provide Eagle files if I had the real stuff to experiment with it.

[planet10]

Originally posted by Eva
It doesn't seem hard at all to produce a new flyback using only the parts from the old one and a new PCB. I could design that PCB and provide Eagle files if I had the real stuff to experiment with it.

I'd be happy to donate a logic board -- but i don't know if it worth the shipping to Europe?

dave

[pinkmouse]

Eva, email me with your location. As I'm getting the ATX supply now, I can send you the downconverter and whatever parts you need from the main PAV board. I'll need to pull off the logic board connector form the downconverter to use for the mod, but all the pins are labelled as you saw so it should still be good for testing. This could be a really useful project for lots of Mac users, though I suppose I should rename the thread "iMac SMPS for Music Server" or something so we are vaguely on topic!