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Standard P4 ATX to 14pin Compaq PSU Conversion

Intro: I saw some pretty cheap half-height compaq desktops (EVO d500 SFF) and decided to buy one to replace the browsing pc downstairs.
Problem: It was missing the psu, and as usual when it comes to compaq it's a non-standard proprietary PSU. In this case with a 14 pin connector. (the mobo was a 252299-001 with 90 deg. angled psu connector on the side sitting straight and parallel with the edge of the PCB, ( please note there has been a report of this circuit NOT working with a different type of 14pin Compaq mobo ) , the pinout for this is here. (looking into connector (not the one on the mobo), with tab on top, pin one is top left first pin, pin 2 is top left second pin, pin 8 is bottom left first pin) I'm not sure but I think there are some other 14pin compaq psu connectors that don't match this) Converting a standard ATX psu is mostly just pinswapping except for 1, 3.3v standby voltage 2, inverted PSON signal 3, fan control lines
I decided to ignore the psu fan control lines, having the psu fan on all the time won't bother me and the effort it would take to get it working right is just not worth it. On to the other two problems. The compaq mobo takes 3.3v and 5v standby voltages, but standard ATX psus offer only 5v. With the 3.3v missing the mobo won't be able to turn the PSU on. There's the option of hardwiring the PSON (perhaps to a switch, which would essentially be like an old AT psu functionality-wise, with the added trouble of having to switch the mobo on/off separately) , but that's highly inconvenient and pretty lame :) So the better solution is a voltage regulator. I chose the LM317 because I had one lying around and because it's easy to deal with. It's an adjustable reg, takes 2 resistors to adjust the output voltage, it's relatively high power (which is completely unneeded here as the load on the 3.3v standby is minuscule) 1kOhm and 1.6kOhm adjustment resistors set the output voltage at 3.31volts, assuming a 5v input ( from the standard atx standby voltage pin ) There's no drop whatsoever while in use, and the reg remains stone cold all the way, so the "heatsink" surface on my pcb is pretty pointless (I know it's on the wrong side, but if it got hot it would be minimally useful regardless :) ) also two caps for filtering were thrown in as suggested by the datasheet.

R1: 1kOhm
R2: 1.6kOhm
R3: 1kOhm
C1: 100nF
C2: 1uF
IC1: LM317
OK1: 4Nxx / TIL116
The other problem is the inverted PSON line, standard ATX psus power on if the PSON line is low, apparently the Compaq PSU is the exact opposite. As described here, I used an optocoupler to act as an isolated voltage controlled switch between PSON at the PSU, and ground, triggered by PSON at the mobo. I later removed the TIL116 from the socket and replaced it with a 4N25 as it had straighter pins (and because the TIL fell out and it took me a few minutes to figure out why the thing wasn't working), but pretty much any optocoupler can be used ( of course, only pin compatible ones in my pcb like 4Nxx )


14 pins (16 here with first column empty)
Final thoughts:
Drill the IN hole (one with the purple wires going into it) with a bigger diameter than the rest as you will have to fit two wire endings in it. (that or change the board design, add another wire pad)
If PC shuts down, front led blinking red It's probably the optocoupler.
If no video, check if the 4pin ATX 12v connector is connected.
Don't take my word for output voltage of the LM317, measure it. 3.2-3.5 should be fine but I'd try to get it as close to 3.3 as possible, just to be on the safe side.
Both standby voltage leds on the mobo should light up upon connecting power to the PSU if you've done everything right.
It would be wise to put this higher up on the cable unlike how I did, or it would also be possible to put it into the psu directly. your choice, (however don't use the hole that the tab of the LM317 is screwed into, to fasten it into the PSU case!! or use some insulating plastic screw as the tab of the LM is VOUT, not GND, so connecting it to GND would not be a good idea)

Eagle brd on request

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UPDATE 2009 01 30:

So apparently some of you are actually building this and having some trouble. I can't say why. This circuit has been working in two of my Compaqs since I built it without a single problem, and I've been using 4N25s in them.. Either way I'm including two images, hope they help.

They show an extra drill hole in the pcb because I added it after the 3rd PCB I made, but if you read the article you'll know what it is.

UPDATE 2009 06 28:

Below the image shows the mobo that I'm using these with, as stated, it probably won't work if your connector, and surrounding pcb doesn't look like this:


Good luck.

UPDATE 2016 10 01:

Ruslans Vojtko sent in this simplified version of the mod (no PCB necessary, uses cheap regulator module off eBay, search for "lm1117 3v3 module")

Thanks, Ruslans!

KVMA docks

I guess time will tell whether this project was actually worth the trouble.
The basic idea was to take keyboard, mouse, audio and VGA, and put it on a single connector that connects to "docks" to which the actual peripherals are connected, so that, when moving my pc between 2 fixed locations I don't have to manually reconnect everything, just that one connector(+ lan and mains).

As usual, pcb making method was PnP Blue.


And the end result:

I'm not releasing Eagles because it was a 5 minute autorouter job ;)

A Smarter Label Printer

Some time ago I won a Seiko Smart Label Printer Plus, on an auction, for a good price. This is an ancient thermal-paper label printer from the still running Smart Label Printer line. It comes with DOS, WIN9x label editor software, which does not run on XP, and Seiko dropped support ages ago (According to the description of a later Seiko software download they dropped support because. "The old serial protocol cannot be supported under windows NT" or something along those lines, which is nonsense), so basically there was no software to conveniently use the printer with. At the beginning I used the Win9x software through VmWare but that's too tedious and annoying. After a bit of research I came across this site, that had full protocol descriptions for both newer and older SLP models. So I ended up coding up a tool that, through a virtual serial port receives data from the new SLP software, in the new protocol(or it can just load BMPs), translates to the old protocol, and sends the translated job to the SLP Plus)


During testing I discovered something. The SLP Plus can print to much wider paper than the SLP Labels. And after I realized that I can't buy SLP Labels locally, and that they would be too expensive anyway for printing shipping labels on, I decided to make use of that. I got lucky because standard width thermal paper used in cash-registers fits perfectly into the SLP :) and they cost $0.50 a roll! as opposed to $7+s/h for two rolls of SLP labels, plus I also get to print more labels this way as I don't always need the full length of an SLP label, and with the paper I can just cut it at any length.


karosium logo in glorious 1 bit per pixel.

I also made a simple support for the new roll of paper that goes in the place of the original label holder from a medicine bottle cap and a plastic rod.

Only disadvantages being that I have to use a glue stick as the paper isn't self adhesive, but I don't really mind that, and that I had to cut the front panel as the opening was only long enough for SLP labels to go through(and the cut didn't really turn out so well), as you see in the picture the serrated plastic bit used to cut the paper doesn't go all the way, only to the width of the SLP Label (that's one on top of the paper) I will have to replace it sometime, with one from a broken printer-calculator or something, but for now I just use an xacto knife to cut the paper.

Now, the newer SLPs of course have a higher dot density (almost twice of the slp plus), so printing from the new software will be oversized, as it can't print dots as close together and as small as the newer ones, but as luck would have it that mismatch is perfect when using the cash-register paper, as it gives about the right size for the print. Also, by using another paper setting the correct size for the SLP labels can be achieved. I basically just have to use smaller label settings than what I actually want to use.

While I don't know why Seiko dropped support for this thing, I think it's similar to the Creative driver shenanigans a couple of months or so back (to boost sales of newer models, and from what I've seen they kept on dropping support for older models in their software ever since the SLP Plus). This product would still be useful, despite being 10 years old, as it's only shortcoming is it's lower dot density when compared to newer models, and IMHO that isn't really a problem, as labels are still clearly readable, and any barcodes made are scannable... Does anything else really matter for a monochrome thermo-label?

So basically, I got a hobby project to work on and a label printer for around $25 shipped, not bad especially considering the prices of the newer SLP printers, or label printers in general.