Re: Vogons members average motherboard collection size

Posted on Yesterday, 18:40

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I have 226 pcs of faulty 8088-486 mainboards boxed up. It's not really a collection, just my passion for repairing bad mainboards running wild. I keep buying them but I don't really have the time to actually look at them. When I see a faulty mainboard for $2-5 I just have to buy it. I only have 25 …

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Re: Coronavirus chatter

Posted on 2020-03-27, 13:50

by

by Miphee

in Milliways

in Milliways

The Hungarian government just ordered the weakest curfew: You can go anywhere (GP, PO, shopping, walking, walking your dog, work, public transport, drive-through restaurants) but you should avoid group gatherings. That is all. Our economy would probably crumble if they issued anything more serious. …

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Re: What is your opinion on these two old AT PSUs?

Posted on 2020-03-24, 15:36

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I usually post an ad on my local electronics forums looking for PSUs and make a bargain. Local auction sites also offer lots of quality PSUs or PC cases with the PSU included. It's much harder to get proprietary IBM, Compaq or HP power supplies from the 80's in decent condition.

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Re: What is your opinion on these two old AT PSUs?

Posted on 2020-03-24, 15:05

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

True, until you come across one of those with steel or lead slabs bolted in, to make the junk feel heavy :D I just repaired an all-steel PSU and yes, damn thing is heavy. :D Can this kind of PSU become decent-ish if you add the missing components? A bad PSU can do too much damage to make it …

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Re: Why is Voodoo 3 so popular?

Posted on 2020-03-24, 11:49

by

by Miphee

in Marvin \ Video

in Marvin \ Video

Because it's all about the nVidia - 3dfx war and the unfortunate demise of the latter. Back in those days you couldn't buy a PC magazine without lengthy articles about the latest gossip about these two. Finally 3dfx crumbled and left a trail of rare&mysterious collector's items (V5 6000, Rampage, V4 …

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Re: What is your opinion on these two old AT PSUs?

Posted on 2020-03-24, 11:14

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The weight of the unit is a telltale sign of quality. Hipro 250W PSU (supplier of IBM): 1715 g Mercury 400W PSU: 847 g It's not a 100% bulletproof test but it's a start.

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Re: What is your opinion on these two old AT PSUs?

Posted on 2020-03-24, 10:08

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Couldn't agree more. Average quality 85° capacitors instead of 105°, minimalistic heatsinks, everything soldered so they didn't have to use connectors, generic PCBs to cut manufacturing costs. Use them at your own risk.

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Re: I blew up my AT PSU, is it worth to repair it?

Posted on 2020-03-23, 13:48

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

What should I remember, and look for, before stating this repair? Is it worth it? I don't think so. Simple non-proprietary PSUs are cheap and not worth repairing. But it's not always about money, it's fun to bring things back to life. If the fuse didn't blow that means that the big capacitors …

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Re: Coronavirus chatter

Posted on 2020-03-22, 06:55

by

by Miphee

in Milliways

in Milliways

Hungary just found the perfect solution to keep the number of confirmed cases down (currently 103). Hospitals simply refuse to perform the covid test on people suspected of having the virus. No tests = no confirmed cases. People with the usual symptoms are simply told to stay at home and only call …

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Re: Bought these games today

Posted on 2020-03-19, 19:48

by

by Miphee

in Milliways

in Milliways

Got another pack of games from my friend, I played some of those as a kid. Well, the demo versions. 😀

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Re: Coronavirus chatter

Posted on 2020-03-19, 15:47

by

by Miphee

in Milliways

in Milliways

People don't give a shit about this at all in Hungary. Well, at least not in the rural regions. Sure, they raid the stores like crazy but they still refuse to stay at home. I'm not talking about people with jobs, I'm talking about the elderly. My wife is a RN and a GP assistant and the waiting room …

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Re: Looking for IBM 4684 reference diskette files

Posted on 2020-03-13, 20:39

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I think I could be onto something: "The DS1218 holds both pin 28 (Vcc) and pin 20 (/CE) of the DS2064 Sram IC at the battery potential (around 3v) when the 5V power is off. This saves the data in the DS2064 Sram and write protects it regardless of the voltages on /CE and /WE pins. In addition notice …

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Re: Looking for IBM 4684 reference diskette files

Posted on 2020-03-13, 16:37

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I tried a bunch of ODD/EVEN ROM pairs (even the original BIOS on a new pair of chips) but none worked. I checked the voltages of the ROM pins and they seem fine so the ROMs are probably OK. System chips get slightly warm so power seems ok, +5V is present on the correct input pins. I noticed one …

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Re: Looking for IBM 4684 reference diskette files

Posted on 2020-03-12, 20:13

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay, so my progress so far: Checked the PSU voltages on the MCA bus and everything is fine. I even found the +38V rail so the PSU seems OK. Checked the RAM the POS came with: working fine. Tested the computer with different RAMs, no change. The attached monitor demagnetizes when I turn the machine …

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Re: Looking for IBM 4684 reference diskette files

Posted on 2020-03-11, 18:45

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Maybe the +38V is for the dot matrix printer that attaches through the back of the PSU. It has several ports there. Still missing the -12V rail.

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Re: Looking for IBM 4684 reference diskette files

Posted on 2020-03-11, 18:01

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I finished cleaning and measuring the PSU. It was insanely dirty but no visible damage to the components. I'm getting very strange readings though: ? means a value that is "jumping around" between 0-300mV. - means a reading below 30mV that is holding steady. I have +5Vs, +12Vs but missing the +38V …

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Re: Looking for IBM 4684 reference diskette files

Posted on 2020-03-11, 13:06

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay, thank you, I'll try.

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Re: Looking for IBM 4684 reference diskette files

Posted on 2020-03-11, 12:23

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Do these ROMs support VGA? The minuszerodegrees site claims they don't. Is there a version that supports a 386 board with onboard VGA?

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Re: Looking for IBM 4684 reference diskette files

Posted on 2020-03-11, 10:21

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That's all true, but when you are desperate enough you just try anything. It was a longshot and failed miserably, but I don't blame IBM at all. They ended their support for this product a long time ago and they allocate their resources as they please. If they don't want to bother with my request …

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Re: Looking for IBM 4684 reference diskette files

Posted on 2020-03-11, 06:52

by

by Miphee

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It was a tough read but IBM's solution to a problem is replacing everything that seems defective. Examine the cables and displays and exchange them. If that doesn't solve the problem, replace the mainboard. It's logical, why would they bother with repairs when they can just get new parts (in 1993)? …

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