You mean things like this?

http://www.ebay.de/itm/ATX-20-PIN-to-AT-P8-P9 … uFSqkmHj4SuUliA

Koltoroc wrote:

You mean things like this?

http://www.ebay.de/itm/ATX-20-PIN-to-AT-P8-P9 … uFSqkmHj4SuUliA

Yes.... It will result in a device for both ATX and AT boards.

Hey, that's my multimetre! So that's where it has been all the time! 😁 (just kidding!)
But seriously, that's a cool project - really looking forward to it.. I wonder which one of the four(?) possibilities you will choose (don't tell yet). 😉

Nice to see a low cost project to solve this. Especially the Sound Blaster 2.0 with CMS upgrade will benefit from this. One of the few cards that require -5V to work.

Minor setback.... Blew something.... 🤣

an lm337 with a couple of resistors + caps will give up a -5v 1.5A output. or chain an 905 (ie: MC7905BTG) and that will give you a direct -5V / 1A output. should cost < 2$ all up or something.

BloodyCactus wrote:

an lm337 with a couple of resistors + caps will give up a -5v 1.5A output. or chain an 905 (ie: MC7905BTG) and that will give you a direct -5V / 1A output. should cost < 2$ all up or something.

I have seen that online somewere too... The problem now, is that I can get -5volt output, the problem is to choose wich gnd I need to connect alongside the -5volt line. If I measure directly on my converter, it is spitting out -5volt. I connect the white wire to the -5v terminal. Choosing any of the black wires will draw too much through the converter I am using. It did survive. I thought I blew it because it is getting too hot. Still working though.

what load/amperage can you pull from your -5v? as for gnd, unless you are doing something funky and floating the gnd or doing a virtual gnd, any ground pin should suffice.

brostenen wrote:

BloodyCactus wrote:

an lm337 with a couple of resistors + caps will give up a -5v 1.5A output. or chain an 905 (ie: MC7905BTG) and that will give you a direct -5V / 1A output. should cost < 2$ all up or something.

I have seen that online somewere too... The problem now, is that I can get -5volt output, the problem is to choose wich gnd I need to connect alongside the -5volt line. If I measure directly on my converter, it is spitting out -5volt. I connect the white wire to the -5v terminal. Choosing any of the black wires will draw too much through the converter I am using. It did survive. I thought I blew it because it is getting too hot. Still working though.

It should not do that, maybe you are doing something wrong? Could you please show what you are doing so we can fix it before you blow something up 😀

Putting together simple negative regulator with a couple of caps should just work.

PhilsComputerLab wrote:

Nice to see a low cost project to solve this. Especially the Sound Blaster 2.0 with CMS upgrade will benefit from this. One of the few cards that require -5V to work.

Roland LAPC-I, Yamaha 718/719, Creative Goldfinch. In all cases -5 is for Line out power, without -5 all these cards are working properly but no sound.

Well.... No ATX psu has blown up (just yet 🤣) Naaa... Just kidding.
Waiting for some feedback from Keropi, before I will post some more.
Perhaps I will get something to work with when I get that reply. 😀

If not, I will let you all know what I have done so far.
All I can say, is that I can convert +12v to -5v and draw up to 3 amp.
(that amp is acording to the spec's from the seller)

The thing I bought, might not deliver the kind of amp what it say it should.
Though being able to convert +12 to -5, makes me think I am on the right path.

Edit...
I have not seen anyone talk about what I am doing. I have not read that this
can not be done this way. Nor have I seen anyone suggesting this aproach.
Hopefully this is a way amoungst other solutions, to -5volt.
If so. It is butt-ugly cheap to make.

At this topic Short on ISA slots? Try this. about multiplication ISA slots there is also very elegant decision for getting -5 volts:



Plug into any slot and you'll get -5 in any other.
By the way jwt27 is offline for much long time. Does anybody know about him? Is all OK?

brostenen wrote:

I have not seen anyone talk about what I am doing. I have not read that this can not be done this way. Nor have I seen anyone su […]
Show full quote

I have not seen anyone talk about what I am doing. I have not read that this
can not be done this way. Nor have I seen anyone suggesting this aproach.
Hopefully this is a way amoungst other solutions, to -5volt.
If so. It is butt-ugly cheap to make.

a small male edge connector that goes into an ISA slot, takes 12v transforms it and then reflows the 5v back into the ISA bus?

Edit : Dammit you beat me to it, PARUS

That is a l7905acv. According to what I can find online, it used negative 12 volt and not positive 12 volt as input.
As -12v rails do not provide enough milliamp, I really need to be able to draw somewhat 500 milliamp from positive 12volt.
I guess the ISA slot solution is a simple one, taken directly from the datasheet. Looks like that. 1xregulator and 2xcap's.

Going for the regulator solution, there must be a simple solution to reverse polarity using off the shelf parts.
Once converted 12 volt positive to 12 volt negative directly, something like a 7905 regulator can be used.

Most AT power supplies had 0.3A max output from -5V anyway, and -12V outputs at about 0.5A to 0.8A.
How much would anyone need -5V for sound cards, 100mA or 200mA tops maybe?

The 7905 in TO220 case generating -5V from -12V would be perfect for that job, as long as it has ceramic bypass caps, some bulk electrolytics and enough dummy load to keep its output stable.

If you want to generate -5V from +12V, +5V, or +3.3V, you need either inverting switch mode voltage regulator or inverting flying capacitor charge pump, both of which are more noisy than linear regulators.

brostenen wrote:

That is a l7905acv. According to what I can find online, it used negative 12 volt and not positive 12 volt as input. As -12v rai […]
Show full quote

That is a l7905acv. According to what I can find online, it used negative 12 volt and not positive 12 volt as input.
As -12v rails do not provide enough milliamp, I really need to be able to draw somewhat 500 milliamp from positive 12volt.
I guess the ISA slot solution is a simple one, taken directly from the datasheet. Looks like that. 1xregulator and 2xcap's.

Going for the regulator solution, there must be a simple solution to reverse polarity using off the shelf parts.
Once converted 12 volt positive to 12 volt negative directly, something like a 7905 regulator can be used.

as I said earlier, use a LM337 to feed the 7905 to get -5v. the LM331 will give you the negative voltage, which the 7905 will make an exact -5v.

or if you dont want to feed the 7905,

an lm337 with +12V input using 2 resistors of 240ohm + 720ohm will give -5v output.

http://ibration.headcrank.com/LM337Calc.php?Vout=-5&R1=240

BloodyCactus wrote:

as I said earlier, use a LM337 to feed the 7905 to get -5v. the LM331 will give you the negative voltage, which the 7905 will ma […]
Show full quote

brostenen wrote:

That is a l7905acv. According to what I can find online, it used negative 12 volt and not positive 12 volt as input. As -12v rai […]
Show full quote

That is a l7905acv. According to what I can find online, it used negative 12 volt and not positive 12 volt as input.
As -12v rails do not provide enough milliamp, I really need to be able to draw somewhat 500 milliamp from positive 12volt.
I guess the ISA slot solution is a simple one, taken directly from the datasheet. Looks like that. 1xregulator and 2xcap's.

Going for the regulator solution, there must be a simple solution to reverse polarity using off the shelf parts.
Once converted 12 volt positive to 12 volt negative directly, something like a 7905 regulator can be used.

as I said earlier, use a LM337 to feed the 7905 to get -5v. the LM331 will give you the negative voltage, which the 7905 will make an exact -5v.

or if you dont want to feed the 7905,

an lm337 with +12V input using 2 resistors of 240ohm + 720ohm will give -5v output.

http://ibration.headcrank.com/LM337Calc.php?Vout=-5&R1=240

It won't work because LM337 can't make positive input to negative output.

It is just an adjustable regulator that can be directly used to get -5V from -12V with correct adjust resistors, so it would be simpler to use just 7905.

BloodyCactus wrote:

as I said earlier, use a LM337 to feed the 7905 to get -5v. the LM331 will give you the negative voltage, which the 7905 will ma […]
Show full quote

brostenen wrote:

That is a l7905acv. According to what I can find online, it used negative 12 volt and not positive 12 volt as input. As -12v rai […]
Show full quote

That is a l7905acv. According to what I can find online, it used negative 12 volt and not positive 12 volt as input.
As -12v rails do not provide enough milliamp, I really need to be able to draw somewhat 500 milliamp from positive 12volt.
I guess the ISA slot solution is a simple one, taken directly from the datasheet. Looks like that. 1xregulator and 2xcap's.

Going for the regulator solution, there must be a simple solution to reverse polarity using off the shelf parts.
Once converted 12 volt positive to 12 volt negative directly, something like a 7905 regulator can be used.

as I said earlier, use a LM337 to feed the 7905 to get -5v. the LM331 will give you the negative voltage, which the 7905 will make an exact -5v.

or if you dont want to feed the 7905,

an lm337 with +12V input using 2 resistors of 240ohm + 720ohm will give -5v output.

http://ibration.headcrank.com/LM337Calc.php?Vout=-5&R1=240

Sweet...
Have not seen that one before. Thanks 😀

EDIT...
What ratings are the caps?

Actually power supplies with -5V have a 7905 built in.