Okay so I need to make better markings on the silk. To keep people from doing this 🤣

People should just follow the silkscreen. If in doubt, look at the schematic to confirm.

Ohhhhh!

That explains it. That didn’t occur to me, -at all-. I generally assemble with my multimeter, and the negative voltages led me astray!

Here is my solution to the P8/P9 AT connector problem:

I used the AT connectors from one of the cheap-o no-negative rail ATX to AT adapters. If you use ferrules on the end, they insert and stay nicely in the connectors on the PCB, once crimped.

- Alex

So, all 5 units work fine, of course, after fixing the polarity. What is everyone doing who is using these boards in ATX cases? I'm building a Socket 5 Pentium into a modern glass ATX case, and of course the power switch is momentary, and not easy to replace.

I'm looking through all the past discussions on this, and the best thing I have found is to just hard-jumper the PSU on, and use the PSU-mounted power switch to turn the system on and off.

- Alex

Well, I suppose that is the next evolution of this, to make a latching circuit.

Not much room left for it 🤔

Perhaps a inline thing that can be shrink tubed?

When is someone gonna build the latest version? Haha :p

I have a latching circuit design on my github.

I finally got around to ordering parts to finish mine up. Now just need to find time

wiretap wrote on 2022-11-07, 03:54:

I have a latching circuit design on my github.

Link me broski! 🧐

ajacocks wrote on 2022-11-07, 02:16:

So, all 5 units work fine, of course, after fixing the polarity. What is everyone doing who is using these boards in ATX cases? I'm building a Socket 5 Pentium into a modern glass ATX case, and of course the power switch is momentary, and not easy to replace.

I'm looking through all the past discussions on this, and the best thing I have found is to just hard-jumper the PSU on, and use the PSU-mounted power switch to turn the system on and off.

- Alex

Usually you can replace the momentary power switch on your case with a regular (latching) switch with the same dinensions.

Have no fear... softpower version. That little Maxim IC fits perfect.

https://github.com/wiretap-retro/PICO-AT-Powe … apter-softpower

😁

Edit: added screw clearance on 3.3v plane (not shown in pics)

layers

This version has clear markings indicating ground as positive for those capacitors btw. so hopefully no more esploded tantrums. 🤣

Also, as you can see I added the device that wiretap discovered also 😀 thanks Wiretap!

BTW:
I have a request about the previous versions that I have uploaded. Please don’t order them anymore. They are nice to have around incase I need to check something or copy/paste something but don’t order them anymore. This goes for the latest one if it has been superseded also, (check future posts) if you already built one that is fine though. 😀

Please use the latest version if you use one of the ones I made.

If you use wiretap’s versions. Ask him what to do. 😀

In general you should use the latest version. Not sure why people in this thread are ordering and building older versions.

I have made the latest fully backwards compatible. You need not populate all its features. It is able to function in any configuration.

wiretap wrote on 2022-03-07, 19:15:

Did some research.. It appears Molex only produced the flat style AT pin header for use with the 90331 connectors. Those flat pin 8619 style connectors were only used on AT motherboards to a certain time period, then Molex discontinued the 8619 and replaced it with the KK 396 square pin connector as seen on the motherboard above, which is compatible with the 90331 connector, as well as KK 396 female connectors obviously. So, the only way to do a board mount connector is to use the one I am using in this design. If the motherboard uses the old 8619 connector, it would need to be replaced with the KK 396 type. So, with the KK396 compatible with both the 90331 and KK396 itself, you lose no functionality with the original connector.

Greetings Wiretap,

The great feature I like about Molex's website is you can choose a connector and it will have a "Mates With/Use With" tab to click. I have some of the latest revision of normal and hi-current at the fab. Rather than change the part on the motherboard, figured I'd build a couple of these with connections for blade or square.

KK series https://www.molex.com/molex/products/family/kk
Mates With/Use WIth feature https://www.molex.com/molex/products/part-det … cles/0009481064

-William

wiretap wrote on 2022-11-08, 20:18:

Have no fear... softpower version. That little Maxim IC fits perfect.

https://github.com/wiretap-retro/PICO-AT-Powe … apter-softpower

pic.png

Is there a BOM with all the mfr or mouser #'s?

NVM made one from the other BOM. Includes a replacement for the molex connector as the original has a 33 week lead time as of 3/29/23.

additonal edit: Out of all my boards none had the square varient of the AT connector, even my newer boards. Picking up the male end of the connecoter as well from mouser.
https://www.mouser.com/ProductDetail/Molex/09 … njDhMjOYncWU%3D

On the question of latching logic for power on, I took an old fashioned approach with mine: I replaced the momentary switch on the case with a latching one of the exact same dimensions (50cents from AliExpress) and fed those wires to PWR_GD.

https://a.aliexpress.com/_mN1I0qQ

Works perfect, the switch latches down like an AT case should, and cost way less than the 74 series logic to build a latch circuit.

The Nov 8 2022 post contains a latching version.