A couple years ago there were apparently ATX 20 pin -5v adapters for sale on eBay (for ISA -5v card requirements). Either nothing like that is available any longer, or I haven't been able to conjure up the magic search terms to see them for sale today.
Does anyone know if anything like that is still available, and if so where? I don't feel I have the skill to go the DIY route, unfortunately.
Thanks!
You might want to check out this project: ATX2AT Smart Converter - Live on Kickstarter!
digger wrote on 2020-09-03, 15:04:You might want to check out this project: ATX2AT Smart Converter - Live on Kickstarter!
Oh that's very cool. I'm looking to provide -5v to an ATX motherboard, not AT, but that's just at the moment. I have a 386 project on the sidelines that could use something like this. I love over-engineered, as long as it's not a car. 😀
I'd recommend the DIY route, nonetheless.
You need a 7905 negative voltage regulator to turn the -12V into -5V. It is a three-pin device that looks roughly like a transistor.
The 7905 needs a 100nF capacitor for its input voltage and another one for its output voltage.
That's it!
Benedikt wrote on 2020-09-03, 15:42:I'd recommend the DIY route, nonetheless. You need a 7905 negative voltage regulator to turn the -12V into -5V. It is a three-pi […]
I'd recommend the DIY route, nonetheless.
You need a 7905 negative voltage regulator to turn the -12V into -5V. It is a three-pin device that looks roughly like a transistor.
The 7905 needs a 100nF capacitor for its input voltage and another one for its output voltage.
That's it!
Could this be done via just a small solderable breadboard? I've soldered before but I've never modified anything before. Do you happen to know where I'd look for any sort of examples of how this is done? I could probably follow along if there was something like a step by step. 😀
It could be done with a small solderable breadboard. Even without, in fact.
If you don't need fancy looks, take a screw terminal strip and call it a day.
Yes, a clean mod would put everything inside the PSU itself, but for a beginner project let's not open that.
I'm not aware of ATX-related examples, but the old and new ATX pinout and the 7905 datasheet should be all you need.
It might be possible to track down an old PSU from the early 2000s which still has -5V.
As an example, take a look at this LC Power 550W which I bought recently. I don't think I have any sound cards which require -5V to test it though.
superkato1k wrote on 2020-09-03, 15:25:digger wrote on 2020-09-03, 15:04:You might want to check out this project: ATX2AT Smart Converter - Live on Kickstarter!
Oh that's very cool. I'm looking to provide -5v to an ATX motherboard, not AT, but that's just at the moment. I have a 386 project on the sidelines that could use something like this. I love over-engineered, as long as it's not a car. 😀
Interesting. So if I understand correctly, your ATX motherboard doesn't require -5V to function, but will pass it through to the proper ISA slot pins if it's provided by the PSU?
As strange as this sounds if you don’t use serial or a modem I have (in some circumstances) just taken a burnt at psu and wired the connectors direct to an atx with it hardwired on and all seemed to work
YMMV
You could also use this module, solder GND to GND, +5V to VIN and it will output -5V on -VOUT pin
https://www.ebay.com/itm/LM2662-Switched-Capa … er/114190379944
you could also add a capacitor (100uF or larger electrolytic rated for 10V or more) on between GND and -VOUT (minus of capacitor to -VOUT, not to GND)
or use this one, it has tantalum capacitors and should be good without external capacitor https://www.ebay.com/itm/LM2662-Switched-Capa … le/323897283334
It should allow more current and will heat less than 7905. But 7905 should be fine if you power supply has resonably strong -12V line. But if -12V is rated for only 10mA or so, I would use LM2662. You could also put a protective Schottky diode between -5V out and -5V cable.
Repair/electronic stuff videos: https://www.youtube.com/c/adalbertfix
ISA Wi-fi + USB in T3200SXC: https://www.youtube.com/watch?v=WX30t3lYezs
GUI programming for Windows 3.11 (the easy way): https://www.youtube.com/watch?v=d6L272OApVg
Benedikt wrote on 2020-09-03, 16:46:It could be done with a small solderable breadboard. Even without, in fact. If you don't need fancy looks, take a screw terminal […]
It could be done with a small solderable breadboard. Even without, in fact.
If you don't need fancy looks, take a screw terminal strip and call it a day.Yes, a clean mod would put everything inside the PSU itself, but for a beginner project let's not open that.
I'm not aware of ATX-related examples, but the old and new ATX pinout and the 7905 datasheet should be all you need.
I'll do a little Youtubin' etc and see what happens. Thanks! 😀
digger wrote on 2020-09-03, 17:25:superkato1k wrote on 2020-09-03, 15:25:digger wrote on 2020-09-03, 15:04:You might want to check out this project: ATX2AT Smart Converter - Live on Kickstarter!
Oh that's very cool. I'm looking to provide -5v to an ATX motherboard, not AT, but that's just at the moment. I have a 386 project on the sidelines that could use something like this. I love over-engineered, as long as it's not a car. 😀
Interesting. So if I understand correctly, your ATX motherboard doesn't require -5V to function, but will pass it through to the proper ISA slot pins if it's provided by the PSU?
Exactly. This particular ATX board's BIOS tracks -5v as well, so it's looking for it, but not for it's own purposes, rather for any ISA cards that may need that fifth B-side pin.
rmay635703 wrote on 2020-09-03, 17:28:As strange as this sounds if you don’t use serial or a modem I have (in some circumstances) just taken a burnt at psu and wired the connectors direct to an atx with it hardwired on and all seemed to work
YMMV
Wow, I wouldn't have even thought of that. And it worked? I don't have a spare AT psu, but definitely an interesting possibility if I were to get hold of one.
adalbert wrote on 2020-09-03, 20:39:You could also use this module, solder GND to GND, +5V to VIN and it will output -5V on -VOUT pin https://www.ebay.com/itm/LM266 […]
You could also use this module, solder GND to GND, +5V to VIN and it will output -5V on -VOUT pin
https://www.ebay.com/itm/LM2662-Switched-Capa … er/114190379944
you could also add a capacitor (100uF or larger electrolytic rated for 10V or more) on between GND and -VOUT (minus of capacitor to -VOUT, not to GND)or use this one, it has tantalum capacitors and should be good without external capacitor https://www.ebay.com/itm/LM2662-Switched-Capa … le/323897283334
It should allow more current and will heat less than 7905. But 7905 should be fine if you power supply has resonably strong -12V line. But if -12V is rated for only 10mA or so, I would use LM2662. You could also put a protective Schottky diode between -5V out and -5V cable.
Oh that's very helpful, thanks for the links as well. I'm going to try and wrap my head around this and see what I can do. And yes, fortunately the PSU is pretty good (Seasonic Gold 650W - smallest reasonably decent PSU I could pick up locally) with pretty beefy 12v. It's got a pretty high-performing 5v rail for a modern ATX, which I was concerned about (though still nothing close to the 5v rail of an early ATX).
Joseph_Joestar wrote on 2020-09-03, 16:58:It might be possible to track down an old PSU from the early 2000s which still has -5V.
As an example, take a look at this LC Power 550W which I bought recently. I don't think I have any sound cards which require -5V to test it though.
I've been keeping my eyes open for an older ATX to be available on eBay, Craigslist, etc. Unfortunately models with -5v drop pretty infrequently, and I'm hesitant to drop $80-100 on a used 20 year old power supply. 🤣 I'm sure I'll catch something eventually!
