Re: What retro activity did you get up to today?

Posted on 2024-03-25, 20:49

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Did some real nice upgrades today on my IBM PS/VP 433 Dx/D (model 6384): Installed a Pentium Overdrive 83mhz processor. At first the bios gave me a "malfunction" error on the Level 1 cache and although the computer posted and detected the processor properly, it was slowwwwwwwwwwwwwwwwww as crap. …

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Re: AST Six Pak Plus - 5150 won't post

Posted on 2024-03-12, 17:34

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay so here is an interesting twist: While I was playing around with the card, checking voltage rails and such, I felt the card after it had been running for a couple minutes - One chip stood out as being a little warmer than the others - A "SN74S280N" which in the picture is the chip directly next …

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Re: AST Six Pak Plus - 5150 won't post

Posted on 2024-03-12, 17:27

by

by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Given the fans and hard disk spin up, but you have no beeps (correct?), doesn't rule out a problem with the card where a particular rail may be shorted. I'd use your ohm meter and check for shorts on all the rails through the card edge connector. https://www.minuszerodegrees.net/5150_5160/MDC/ …

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Re: AST Six Pak Plus - 5150 won't post

Posted on 2024-03-12, 17:27

by

by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

BitWrangler wrote on 2024-03-12, 15:48: Did you try disabling the top two banks to see if it works at 256/512 like the other board does... or tried it with only one bank? Yes tried with no difference. Even disabled all banks on the Six pak card with same results

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AST Six Pak Plus - 5150 won't post

Posted on 2024-03-12, 15:18

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Wondering if anyone can help me with this one: Working on my IBM 5150 (Rev B). I got this AST Six Pak Plus in a box of random parts and I wanted to try using it for this machine. Unfortunately when this card is placed in the machine, it won't post. The power supply, hard drive still power on/spin up …

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Replacing Composite/RCA jack on IBM CGA card

Posted on 2024-01-20, 14:40

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by polishvito

in Marvin \ Video

in Marvin \ Video

I have an IBM CGA card from a 5150 that I am working on restoring. The composite output jack is pretty crusty/corroded and the monitor I am using has difficulty syncing up and/or video just randomly cuts out, comes back blurry (even for composite). I’ve cleaned the connector as best I could, used …

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Re: Portable PCIII bad VRAM?

Posted on 2023-10-18, 17:52

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You can still slide fingers over the pins of every chip except the pins where the 6MHz crystal connect to, since the finger will disrupt clock signal generation and the card will definitely misbehave when that is happening lol. If you find something that causes the garbage to be affected …

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Re: Portable PCIII bad VRAM?

Posted on 2023-10-18, 14:16

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

In that case you would want an oscilloscope and start looking at the individual signals, perhaps some output from a logic chip is bad. Perhaps finger test can help too, since bad signals usually will be affected by presence/contact with a finger and it can help to zone in on where the fault may be. …

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Re: Portable PC III Video fault

Posted on 2023-10-18, 03:49

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by polishvito

in Marvin \ Video

in Marvin \ Video

giantclam wrote on 2023-10-18, 00:32: Are all the pins attached to board? […] Show full quote Are all the pins attached to board? Seemed to be solid to me, but since you brought it up I went over the whole chip with the soldering iron. No change.

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Portable PC III Video fault

Posted on 2023-10-18, 00:14

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by polishvito

in Marvin \ Video

in Marvin \ Video

I have been working to restore this Portable PC III - apparently made by Origin Systems. All in one 12mhz 286, 1mb ram, and this amber display. Aside from a disassembly and deep cleaning, I’ve done a few repairs so far: IMG_1424.jpeg - motherboard caps exploded on first test so recapped the whole …

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Re: Portable PCIII bad VRAM?

Posted on 2023-10-17, 18:56

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Socket won't do harm, any replacement parts might be having bad bits in them too so it is good to be ready for that. Welp you were right. Replacement chips came from eBay faster than I expected. I socketed the old ones and put the new ones in, and the behavior is exactly the same. Even if the new …

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Re: Portable PCIII bad VRAM?

Posted on 2023-10-16, 19:48

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

U25 and U31 (the Sharp branded chips) right under the Yamaha chip are the DRAMs for video stuff. There should be plenty of suitable parts to use although I cannot give any exact part numbers. 64Kbit sized and 4bits wide, 120ns or faster access time. But the stuff on the images suggests some kind of …

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Portable PCIII bad VRAM?

Posted on 2023-10-16, 15:32

by

by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Could use some help with this one. I picked up this very odd little luggable machine: IMG_1424.jpg IMG_1427.jpg The Portable PC III. Seems to be made by Orchid Systems. It is a weird beast. It has a generic (G2 chipset) 12mhz 286 MB with 1mb ram onboard. There is very little in the way of …

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Re: Tantalum Cap ID on SYSGEN 1050 floppy riser card for PS/2 Model 50Z

Posted on 2023-09-22, 09:51

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

giantclam wrote on 2023-09-16, 23:37: Replace all 3 (C5/C7/C8) ...if C5 is also 4.7uf/35v then that's likely the value - you can use electrolytics Yep that’s what I ended up doing. Riser card works fine.

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Re: Some questions about IBM PS/2 Models

Posted on 2023-09-16, 16:40

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I made some progress. First at all that cmos adapter also not really work for me. Sometimes the system dont even boot. So i mod the dallas and i got the 165 163 error on startup, so should be ok now. But my floppy looks not so good. It try to read, but i got read error with the ref floppy disk. So …

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Tantalum Cap ID on SYSGEN 1050 floppy riser card for PS/2 Model 50Z

Posted on 2023-09-16, 16:27

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

As the title says - trying to find an ID on this exploded cap. I took apart/serviced this Model 50Z and discovered on the floppy riser card this cap let loose. Almost missed it at first, but I saw a burn mark on the PCB and traced it upwards. The cap right next to it appears to be a 4.7microF 35V so …

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Re: Some questions about IBM PS/2 Models

Posted on 2023-09-08, 23:29

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

oh thats nice and clean! "Im a bit afraid after all that messages." MEH. Dont be. All retro computers have quirks. IBM's quirks are (usually) well documented and intentional. I don't suggest PS/2 for first time retro, only because the clones are usually much more common and thus cheaper. They have …

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Re: PS/2 P70 MCA Conflict - Resound New Wave MCA and MCIDE

Posted on 2023-09-07, 18:44

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Got a solution! Thanks to Mark from ZZxio who made the MCIDE and responded to me very quickly. it looks like there was an error with Texelec’s ADF file. ADF: Choice "220h" pos[1]=xxxxx010b io 0220-022fh This works fine with other adapters e.g. NIC cards, but seems when using the McIDE card, the auto …

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Re: IBM PS/2 P70 "110 ?????" Error. ? Memory problem

Posted on 2023-09-07, 15:14

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay so the results are in. And.... I am a dumb ass. A really big dumb ass. So much so that I don't even really want to post about it but I figure I owe to anyone in the future who is looking at similar issues. I open it up and start taking out the ram sticks. My plan was to reinsert one at a time …

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PS/2 P70 MCA Conflict - Resound New Wave MCA and MCIDE

Posted on 2023-09-07, 15:04

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by polishvito

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I'm conflicted. Or rather my P70 is conflicted. So I got and have been trying to restore this PS/2 P70. One problem after another of course. Totally dead HD so I got the MCIDE (https://zzxio.com/product/mcide/). Works great, boots off CF card etc. I ordered the Resound New Wave MCA https://texelec. …

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