Anyone enough of an electrical engineer to know how to convert say the 3.3v volt on the psu to -5v we need for TT and megaSTE? also old IBMs etc..
There was a guy selling a cable on ebay.. no longer.
I got some perfect sized ATX power supplies. I just need to create the -5v somehow.
James
-5v - from an ATX psu?
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Re: -5v - from an ATX psu?
ATX has a -5v rail. If its not powerful enough use a 7905 regulator.Bikerbob wrote: ↑Wed Dec 11, 2019 9:45 pm Anyone enough of an electrical engineer to know how to convert say the 3.3v volt on the psu to -5v we need for TT and megaSTE? also old IBMs etc..
There was a guy selling a cable on ebay.. no longer.
I got some perfect sized ATX power supplies. I just need to create the -5v somehow.
James
http://powersupply33.com/atx-power-supply-pinout.html
———
"It is not necessarily a supply voltage at no load, but the amount of current it can provide when touched that
indicates how much hurting you shall receive."
"It is not necessarily a supply voltage at no load, but the amount of current it can provide when touched that
indicates how much hurting you shall receive."
Re: -5v - from an ATX psu?
Every ATX I am looking at does not have -5v.. maybe its still in there but not being brought out to the plug.
What I am reading is ATX ver3 standard did away with the -5v.
This was in the link you provided...
The ATX power supply generates three main voltage outputs that are: +3.3 V ; +5 V ; and +12 V. Low-power −12 V and +5 VSB (standby) supplies are also generated by this power supply. The −5 V output was originally needed since it was supplied on the ISA bus, however it became obsolete with the removal of the ISA bus in modern day PCs and has been removed in later versions of the standard ATX power supply.
James
What I am reading is ATX ver3 standard did away with the -5v.
This was in the link you provided...
The ATX power supply generates three main voltage outputs that are: +3.3 V ; +5 V ; and +12 V. Low-power −12 V and +5 VSB (standby) supplies are also generated by this power supply. The −5 V output was originally needed since it was supplied on the ISA bus, however it became obsolete with the removal of the ISA bus in modern day PCs and has been removed in later versions of the standard ATX power supply.
James
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Re: -5v - from an ATX psu?
You need the regulator then. 7905 type job.
———
"It is not necessarily a supply voltage at no load, but the amount of current it can provide when touched that
indicates how much hurting you shall receive."
"It is not necessarily a supply voltage at no load, but the amount of current it can provide when touched that
indicates how much hurting you shall receive."
Re: -5v - from an ATX psu?
SO found this.
https://czh-labs.com/audiowind-5v-dc-ne ... p0695.html
but the -12v output on the PSU is only .3 amp.. will that power this circuit and whatever else it needs?
James
https://czh-labs.com/audiowind-5v-dc-ne ... p0695.html
but the -12v output on the PSU is only .3 amp.. will that power this circuit and whatever else it needs?
James
Re: -5v - from an ATX psu?
terriblefire, I assume you have some pretty good electrical knowledge because of the boards your building etc.. maybe thats what you do for a living.
In the ST world the TT and the megaSTE use -5v on their PSU .. hard to find now.. I have found a nice size replacement a Delta DPS-88ab-2 but it does not put out -5v. Would there be a small circuit you might suggest using that 7905 that could do that?
The board I found needs low ac input or negitive voltage input. the output on the -12v rail is only .3amp.. How do I calc what would be used in running this board.. still left for what the computer needs.. and is it enough for the -5v supply??
James
In the ST world the TT and the megaSTE use -5v on their PSU .. hard to find now.. I have found a nice size replacement a Delta DPS-88ab-2 but it does not put out -5v. Would there be a small circuit you might suggest using that 7905 that could do that?
The board I found needs low ac input or negitive voltage input. the output on the -12v rail is only .3amp.. How do I calc what would be used in running this board.. still left for what the computer needs.. and is it enough for the -5v supply??
James
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Re: -5v - from an ATX psu?
There are definitely inverting linear regs out there. I'd remembered 7905 from my uni days but maybe its a different part.
Ian Steadman did a nice version for the amiga that produces all the right voltages.
http://www.ianstedman.co.uk/Amiga/amiga ... ATXAdaptor
I have one. I dont tend to do power supplies myself as they are complicated and need a lot of time and energy.. and unless you're doing something specific like @exxos does for the ST/E its usually just worth buying off the shelf.
Ian Steadman did a nice version for the amiga that produces all the right voltages.
http://www.ianstedman.co.uk/Amiga/amiga ... ATXAdaptor
I have one. I dont tend to do power supplies myself as they are complicated and need a lot of time and energy.. and unless you're doing something specific like @exxos does for the ST/E its usually just worth buying off the shelf.
———
"It is not necessarily a supply voltage at no load, but the amount of current it can provide when touched that
indicates how much hurting you shall receive."
"It is not necessarily a supply voltage at no load, but the amount of current it can provide when touched that
indicates how much hurting you shall receive."
Re: -5v - from an ATX psu?
Theres a neg-gen in the STFM circuit, generates -12 for the RS232.. I have looked into it before recently , but I haven't found any good solution to this. You either have to have a proper PSU with the voltages you want or build a small circuit using a transformer and a 7905.
http://www.theorycircuit.com/dual-power-supply-circuit/
http://www.theorycircuit.com/dual-power-supply-circuit/
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
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Re: -5v - from an ATX psu?
That's 4 watts. So at -5V that would be just under an Amp, minus conversion loss, so say 750mA. Is that enough?Bikerbob wrote: ↑Wed Dec 11, 2019 10:23 pm SO found this.
https://czh-labs.com/audiowind-5v-dc-ne ... p0695.html
but the -12v output on the PSU is only .3 amp.. will that power this circuit and whatever else it needs?
James
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
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Re: -5v - from an ATX psu?
NIce...
Here is more info on the Ian Stedman stuff... including a github link with all his schematics.
http://www.ianstedman.co.uk/Amiga/desig ... aptor.html
I distinctly remember creating -5V from 5V with a 7905.
Here is more info on the Ian Stedman stuff... including a github link with all his schematics.
http://www.ianstedman.co.uk/Amiga/desig ... aptor.html
I distinctly remember creating -5V from 5V with a 7905.
———
"It is not necessarily a supply voltage at no load, but the amount of current it can provide when touched that
indicates how much hurting you shall receive."
"It is not necessarily a supply voltage at no load, but the amount of current it can provide when touched that
indicates how much hurting you shall receive."