Found some info on this - https://allpinouts.org/pinouts/connectors/pow … -supply-13-pin/

"Non-standard ATX MB power connector with additional 6-pin Molex for 3.3V

Single-in-line Molex-like 13-hole connector with one hole empty. Looking on the metal latches side of the connector, wires UP, “1st” pin is on the LEFT. PSU’S Additional 6 pin Molex 3.3V connector pinout is BLACK WIRES=GND, BROWN WIRES=+3.3V

"

so close!
not sure if anyone has any experience with these HP Vectra motherboards.

Got a HP Vectra power supply on eBay, and the 13 pin connector fits perfectly, now there's this additional connector that has 3.3v wires.. but it's a different size than pins on my motherboard...

Wondering what would happen if I powered this thing without the 3v molex plugged in?

http://pinouts.ru/Power/hp_vectravl5_power_pinout.shtml

That link shows the 6 pin 3.3volt connections. Is the CPU running 3.3volts? Unfortunately when dealing with proprietary connections it isn't easy. I feel your pain. Here is something that might work but unsure of the pitch, etc.

www.mouser.com/ProductDetail/TE-Connect ... mJnE4Pw%3d

Thank you for the reply and the connector link!

Processor is A80486SX-33 which I believe is 5v?

Not exactly sure why the board needs the connector, but will wait on turning it on until I know for sure. Don't want to do anything to damage the board 🤣

Your right, cpu-world shows that CPU to be 5volts. Not sure if the 3.3v is just for future low power cpus or what. I honestly am not sure what would use 3.3volts in a 486 system other than memory or cpu and I figure most items of the day would have a regulator to accept 5v. I have a gut feeling it would power on without the 3.3, but I also have let the magic smoke out more than once.

haha yeah that's what I was worried about. I've done that a time or two myself 🤣

Based on the pinouts.ru site, I was originally thinking that the power supply I bought was for a newer version of this motherboard. It has the 13 pin connector which connects perfectly, and I figured the side connector is the same voltage and number of pins but different connector size.

However, i'm looking at this video of a Vectra with the same exact processor, and those 6 pins actually go to a ribbon cable attached to the front panel.
https://youtu.be/4Y8XdZqrRw4?t=877

That's the exact position of the 6 pin connector on mine (you can see a couple of those components between the two have been moved from one revision of this motherboard to the next (not sure what those yellow things are):

Maybe that 6 pin "PS2" molex is just not used on my motherboard - maybe it was for a very similar motherboard that just had a 3.3v CPU 3.3v and 3.45v 486 Motherboards

That would answer the question as to where to connect the power/reset cables connectors - i'll have to experiment with those to see what's what, unless there's a manual out there that lists out that pinout.

Just turn it on, that small header is likely for the front panel connections. A 486 board usually doesn't use 3.3v, the power supply is likely from a newer machine that does.

beastlike wrote:

(you can see a couple of those components between the two have been moved from one revision of this motherboard to the next (not sure what those yellow things are)

The yellow surface mount components are small value capacitors, presumably in parallel. They might have swapped one larger cap for two smaller ones (the sum of their capacitance being about the same as what they replaced) for a wider filter band. Alternately, they might have done the opposite if the design tolerated it to save an extra component, some assembly, and therefore cost.

NJRoadfan wrote:

Just turn it on, that small header is likely for the front panel connections. A 486 board usually doesn't use 3.3v, the power supply is likely from a newer machine that does.

Not only that, the 3.3v supply is almost always on the board. My EXP-4045 has a 3.3v VRM for DX4 CPUs

gdjacobs wrote:

beastlike wrote:

(you can see a couple of those components between the two have been moved from one revision of this motherboard to the next (not sure what those yellow things are)

The yellow surface mount components are small value capacitors, presumably in parallel. They might have swapped one larger cap for two smaller ones (the sum of their capacitance being about the same as what they replaced) for a wider filter band. Alternately, they might have done the opposite if the design tolerated it to save an extra component, some assembly, and therefore cost.

Interesting, thank you!

NJRoadfan wrote:

Just turn it on, that small header is likely for the front panel connections. A 486 board usually doesn't use 3.3v, the power supply is likely from a newer machine that does.

Awesome. I don't actually have the case to this one, so I was gonna just rig something for now. I'm assuming 2 pins are power, 2 are reset, and 2 are either HD light or power light.

This might not apply to you, but iirc there was a DEC Alpha motherboard which featured a similar extra power plug and PCI slots. Iirc the 3.3v power plug on this particular board (DEC Alpha AXPPCI 33) was used specifically for its PCI slots. I never managed to power on this board though, but perhaps the 3.3v power plug on your board isn't necessary for what you intend your board to be used for.

Just my €0.02

Tetrium wrote:

This might not apply to you, but iirc there was a DEC Alpha motherboard which featured a similar extra power plug and PCI slots. Iirc the 3.3v power plug on this particular board (DEC Alpha AXPPCI 33) was used specifically for its PCI slots. I never managed to power on this board though, but perhaps the 3.3v power plug on your board isn't necessary for what you intend your board to be used for.

Just my €0.02

Interesting.. There's an ISA riser board, I'll have to check if that's got anything like that. Thank you!