Replacing Compaq Portable 486/66 PSU with ATX4VC
Posted by ifoindecks@reddit | vintagecomputing | View on Reddit | 6 comments
Hello! I have a Compaq Portable 486/66 and when I turned it on, I saw a flash from the PSU. I think the fuse blew up, but I can't see anything else obviously wrong in the PSU (no leaking capacitors or blown up tantalums), and I don't know how to debug it. So I was thinking of replacing the PSU with an ATX4VC.
The problem is that I don't know the pinout of the PSU connector. The PSU has the markings "Compaq assy no 128764" and "Compaq spare number 128898-001". Does anybody know the pinout of this connector? Thanks!
Js987@reddit
Frustratingly it is not in the service manual: http://www.bitsavers.org/pdf/compaq/Compaq_Portable_486/Compaq_Portable_486c_-_Maintenance_and_Service_Guide.pdf
ifoindecks@reddit (OP)
Yes 🤔 I would rather buy something new for this machine, because the refurbished components probably break down soon as well
NorCalFrances@reddit
If the cost of the refurbs or just a used but working psu is not outrageous you could buy one and get the voltages off it. Write the pinout on it with a sharpie. Run it til it fails someday and then you'll have the info you need.
Low-Charge-8554@reddit
This MAY help - scroll down to Compaq section. https://pinoutguide.com/Power/
ifoindecks@reddit (OP)
Thank you, the pin shape layout does match the "Compaq 810, 810e, 820 chipset motherboard power connector" and "Compaq BX chipset motherboard power connector" - this is a good starting point!
Js987@reddit
Annoyingly, Compaq really liked that 14-pin Molex and used it with several pinouts. The BX and 810 chipsets were Pentium II/III/Celeron era machines. But I agree, it’s a good starting point, and I learned a bunch about the Compaq supplies I didn’t know before, including finding projects like this: https://www.karosium.com/2008/05/standard-p4-atx-to-14pin-compaq-psu.html
The biggest issue I see with your plan to use an ATX is that apparently a lot of these 14-pin Compaq supplies invert the PSON line compared to what’s normal with an ATX power supply. Personally, I’d probably buy one of the refurbs and then use it for a project to make a replacement supply, as these are super cool systems and having an open source PSU replacement would be great.