VOGONS


First post, by Kiteless

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Greetings, I searched around on the forums and wasn't able to find the answer so hopefully someone can point me at a thread that already covered this exact topic. I recently got my hands on an elusive (for me anyway, and not ebay prices) 386. This one is a 386 DX33. With all the old hardware and PSU it actually boots up fine. I plan on doing a "resto-mod" do it. Swap all caps, especially tantalums, replace Dallas Clock with a modern solution and use a new ATX PSU.

So here is my question: I read that modern PSU's have a weak if not totally nonexistent -5v rail and that AT PSU's are much stronger on their 12v side than the 5V side as older PC's are more 12v dependent (or maybe I have that backwards). As I understand it a weak or missing -5v on a modern ATX PSU is generally not a problem except certain ISA add on cards like a sound card need -5v to work. 1. Is this all true? Are these things I need to be keeping an eye out for? 2. Can anyone tell me just how powerful a particular rail should be to comfortably run a 386 DX33 and also a 486 DX4 100? 3. If -5v is critical what is the minimum current I should be looking for there?

I have a new old stock AT PSU powering my 486 build and it's been working absolutely fine but it's still like 20-25+ years old so I want to replace that PSU with something modern and solid. Some of these computers I'm planning on keeping till they crumble into dust and fine with buying like a really nice Seasonic for them. Any help/guidance would be super helpful. I've had a heck of a time tracking down more details on this. Below is the adapter I purchased to do this. Thanks all!

https://www.ebay.com/itm/7-7-Inch-ATX-20-Pin- … er/222659331521

New videos at least every 2 weeks
https://www.youtube.com/channel/UCTfnRX4AWhbYJuguUcEff-g

Main Systems
NuXT
IBM 5140
486 DX4 100Mhz (Mainly DOS)
AMD K6-2 500Mhz (Mainly DOS)
AMD Athlon 700Mhz 9700 Pro (Win 98)
Pentium D 3Ghz 4670 AGP 8x (Win XP)

Reply 1 of 6, by TheMobRules

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Only a few ISA sound cards require the -5V line, otherwise it's not needed at all and it was removed from the ATX standard years ago. There is a thread somewhere in this forum which lists the sound cards that need -5V. If you find that your card is one of those, you could still buy an ATX-to-AT adapter which generates -5V from the -12V line, these are usually sold on eBay.

For 386 and 486 PCs you don't need much power, unless you're running a workstation/server with lots of drives. Any modern power supply should be able to handle it with ease.

Can you post pictures of your NOS AT PSU? If it's decent, I would keep it instead of buying a new one. I'm generally in the camp of refurbishing old AT PSUs rather than buying modern ones (assuming they're well built). Normally this involves changing capacitors and replacing the fans, but in case of new old stock ones a quick check-up should be fine. I just don't like how the newer units affect the "vintage" look (they're generally black, with fan on the bottom and tons of useless SATA/PCIe connectors).

Reply 2 of 6, by Kiteless

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Hey thanks for the quick reply. I'll keep searching for that -5v sound card list. Haven't found it yet. I think the search engine works similar to google when putting a "-" in front of something means one doesn't want to include it in search. So I have been searching for "5v soundcard/sound card". I forget what sound card the 386 has in it right now. Possibly not something that I would keep, it posts but I didn't let it stay on long, was a quick smoke test. It's really grungy and the fan in the PSU doesn't spin as it's all nasty inside. The mobo is surprisingly clean and the cards, being horizontal in the little squatty mini-tower are just a bit dusty. In addition to the stuff I mentioned above, the machine will get a full tear down including cleaning and lubricating the floppy drives and any new fans 😁

As for the NOS PSU it's some super cheapo no-brand PSU I got out of an NOS full tower AT case. A friend wants to do a reverse sleeper in it. Powerful modern PC in a 4' tall beast. haha.

And yeah not much power needed for these old rigs. Will have 2 floppy drives, maybe a CD ROM and will probably go SD-IDE adapter like I have done on anything WIn95 era or older. Actually runs WIn98 fine too on one of those adapters. That said I would love to put the smallest SATA drive in it I can fine with a SATA-IDE adapter just to get those authentic HDD noises but I doubt the BIOS would see more than a fraction of it, if it works at all. Will yank the modem and maybe add a DOS packet driver compatible NIC. Will probably toss in an old Sound Blaster 16 of some kind. Not sure yet. Anyway I mention all this to give you an idea of what's going to go in it. Thanks again!

New videos at least every 2 weeks
https://www.youtube.com/channel/UCTfnRX4AWhbYJuguUcEff-g

Main Systems
NuXT
IBM 5140
486 DX4 100Mhz (Mainly DOS)
AMD K6-2 500Mhz (Mainly DOS)
AMD Athlon 700Mhz 9700 Pro (Win 98)
Pentium D 3Ghz 4670 AGP 8x (Win XP)

Reply 4 of 6, by Kiteless

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imi wrote on 2020-02-14, 20:46:

Hey thank you! I was totally not doing the search correctly. Cheers!

New videos at least every 2 weeks
https://www.youtube.com/channel/UCTfnRX4AWhbYJuguUcEff-g

Main Systems
NuXT
IBM 5140
486 DX4 100Mhz (Mainly DOS)
AMD K6-2 500Mhz (Mainly DOS)
AMD Athlon 700Mhz 9700 Pro (Win 98)
Pentium D 3Ghz 4670 AGP 8x (Win XP)

Reply 6 of 6, by Vynix

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If you're worried about the -5V rail, there are some industrial ATX PSUs that still have a -5V rail such as the Bicker BEA-630 among others. Though finding one of these units for sale is easier said than done.

Proud owner of a Shuttle HOT-555A 430VX motherboard and two wonderful retro laptops, namely a Compaq Armada 1700 [nonfunctional] and a HP Omnibook XE3-GC [fully working :p]