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Hardware

ISA Voltage Regulator Cards? 20

Posted by Cliff from the electric-current-traffic-cop dept.
stripey357 asks: "I'm trying to install a Dialogic Gammafax card in Pentium-based SCO unix box, and I've run into a problem. The power supply for this box doesn't supply -5v to the ISA, and that's the voltage the Gammafax wants. Do they still make ISA voltage regulator cards that can reg -12v down to -5v, or would it be easier to replace the power supply?"
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ISA Voltage Regulator Cards? More

ISA Voltage Regulator Cards?

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  • Possible solution... (Score:3, Informative)

    by cr0sh ( 43134 ) on Thursday September 20, 2001 @08:01PM (#2328134) Homepage
    Not sure if this will work or not...

    If it is just that card that needs it, and you know which pin it is on the ISA card, you might be able to do it yourself, with a little work:

    The power supply should have a -12 volt line (or even a -5V line, which is easier) - find the pin(s) on the ISA card that need the voltage, trace each one back to a solder pad (or you might have to scrape the trace). Cut the trace with an xacto knife to keep voltage flowing into the motherboard (unless you know that it is routed properly - better safe than sorry). If you need to scrape the trace, do it with the knife as well. Apply some solder, add the wires you need, bring 'em together at one point, and hook up the -5V if you have it from the PS, or if you only have -12V, used a -5V regulator (sorta like the 7805, which is a +5V regulator - they make the opposite, can't remember the part number).

    Of course, this invalidates all warranties, and it could cause other problems - it is a hack, plain and simple, I am just offering it to you as a possibility and learning advice - don't blame me if your motherboard/fax card/power supply blows up...

    I hope this helps... Good luck!
    • If you're going to solder, get one of those little DC/DC convertors in a black epoxy brick that makes -5V from +5V or +12V.

      If you're really cheap, some old ethernet cards have isolated 5V to 9V convertors in them. Use one of them and a 7805 to get an isolated 5volts. Tie the isolated +5V to system ground, and the ground from the 5volt supply will be at -5V.

    • At least, don't if you have a free ISA slot.

      ISA is a bus - all the pins on all the slots are wired to each other, straight across. Go to an electronics shop, get an ISA perfboard card, put the regulator on that, and have it supply power to the other slots.

      That way, if it doesn't work, and there is no smoke discoloration, you can hide your tracks if you need to send it back for warranty repair :)

      • You make a good point, but that was why I suggested cutting the trace, and soldering "above" the cut.

        However, I do like your solution - much sneakier in case something goes wrong...
      • The above is the best solution proposed so far, provided that your motherboard actually has the traces for the -5V bus. If the power supply doesn't provide that voltage, they may have decided to save a little money by not including it. Does this beast use a standard power supply to motherboard connector--AT or ATX type?--or something proprietary?
  • I use a Gammalink Fax board (CP4-LSI) in a server at work. Not sure if this will help you, but I use a DFI/ITOX GITOX3 Motherboard

    http://www.itox.com/pages/products/Mothers/ItoxM B/ Itox3Spec.cfm

    The board gives me 5 ISA Slots and 2 PCI Slots in a ATX chassis, and has been extremely reliable. Replacing the motherboard might be the easiest solution. If you are able to, you could change the card, the CPi400-LSI may work.

  • Do they still make ISA voltage regulator cards that can reg -12v down to -5v?

    You're looking for a 7905 regulator, provided the card does not require more than 1A. These regulators are quite common LSI devices used in hobbyist electronics, they can be found at Radio Shack. Several firms manufacturer 7905's, here are some datasheets: Installation is relatively simple. Pin 1 connects to ground, pin 2 to -12V, and pin 3 to the -5V line (this is the output). 7905's are often in a TO-220 package which allows you to screw on a heatsink if needed. Be sure to apply thermal grease to increase heat conductivity.
  • Is the motherboard designed without any way to power the -5V line on the ISA bus, or does the power supply not provide it?
  • First of all, my initial advice would be to do what the people above are saying about getting a -12 to -5 regulator and I would say to just solder wires from the regulator to the bottom pins of an ISA slot so all your slots have -5, assuming that the -5 pin is just a no connect on the mother board. And then just use some thermally conductive Lock-Tite or something like that to glue the regulator to some metal part to disipate heat.

    My second idea is, and this is a long shot, I know that companies like az-com [az-com.com] and catalyst [catalyst-ent.com] make ISA active extenders which you can use for hot swapping cards, but you can also supply external power and I think regulated power, from which voltages I wasn't able to find out. I can't remember if the ISA ones did have regulators, I know the PCI ones had regulators for using 3.3v cards on 5v etc... The down-fall of these is first of all, the card will no longer fit in the case and secondly they cost around $200-$300...well at least they used to, maybe they're not in demand as much anymore.

    Hope that helps..
  • Not the smartest way to do it, since you can explode a power supply. I had a line conditioner (Tripplite) that I was able to tweak a small rheostat and jack up it's output voltage. So the conditioner output more than the standard 120v(I think I ran it at 123v). This in turn made the transformer in the power supply output the 5v I needed. Although it worked for me this is dangerous, try at your own risk.

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