Hi all,

My name's Jim and I'm a hobbyist ham radio operator. The project I've just started is to convert an old ATX power supply into a variable voltage supply. I've located the ic's numbers and have been trying to locate data sheets so iIcan identify the pin outs but I cannot find any information on the internet. I'm possibly looking in the wrong place. The ic numbers are UTC3845D, UTC7608D. If anyone could point me in the right direction I would be ever so grateful.

Jim

This might be history to you now but I am having the same problem re this IC. I can order millions of the little B's if I want them but nobody seems to have a data sheet and I am struggling to work out what pin does what. I am trying to repair a PC power unit and I prefer to analyse the fault rather than just blanket replacement of all the components. Do you have a data sheet you could help me out with ? This IC appears to be in the standby / start up section of the PSU.

Mod: link to old thread
https://forum.allaboutcircuits.com/threads/datasheet-stuggles.155528/post-1341228
For those that are about to panic and say don't do it. I am an electrical engineer with a separate background in electronics and used to working at 400,000 volts on the UK national grid so I am very well aware of safety issues and the need to work safely inside what is a unit that runs almost directly across the mains in what I would describe as "a death or glory design".

Chris

 

Have you even tried a Google search?
#2 Google Hit for "3845 datasheet"
https://www.ti.com/product/UC3845

#2 Google hit for "UCC7608 datasheet"
https://www.ti.com/lit/ds/symlink/ucc2808-1.pdf?ts=1653576094317&ref_url=https%3A%2F%2Fwww.bing.com%2F

You're still going to struggle with working out how these chips work. I've been at it for a decade and I'm still not on terra firma.
Good luck with your project

 

You can always add a variable regulator at the fixed output of the ATX supply, either a linear type for small currents, or a switching type for larger currents.
For voltages higher than the ATX output, you could use a buck/boost switching regulator.

That's a lot easier (and more likely successful) than trying to hack the ATX.