Re: Fixing Dallas battery on 486 motherboard.

Posted on 2022-02-23, 10:06

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hey Guys, I have another NOS 486 motherboard with a Dead Dallas. It does not have connection pins for an external battery but the markings are there for a jumper and traces for an external Battery connection. PLEASE SEE PHOTOS. I was wondering if I could add an external battery by soldering onto …

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Re: Early P5 + P54C (Socket 4 + Socket 5) mainboard

Posted on 2022-02-21, 22:58

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Have you tried testing combinations of JP32 and 34 in case they make a difference, since they seem to be connected to the VL/PCI bridge. Or the JP16/17/19 since I don't think we know what they do.

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Re: SUCCESSFUL K6-2+ to K6-3+ Full Cache Enable Mod

Posted on 2022-02-21, 18:28

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Nice example of a little bit of knowledge being misleading. I was sure those were just low inductance capcaitors https://www.kyocera-avx.com/products/ceramic-capacitors/low-inductance/ . Tricksy/clever of AMD to hide their configuration resistors in with what I still assume are some capacitors. …

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Re: Bought these (retro) hardware today

Posted on 2022-02-21, 18:09

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Think maybe this is Packard Bell version rather than the Dell one: https://www.ultimateretro.net/en/motherboards/5897 ?

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Re: Anyone know the polarity on the 3 leg tantalums in an IBM PS/2 type 8525 (Model 25). Color monitor/8086

Posted on 2022-02-21, 15:18

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yep, that says there's a short from -12V to Ground. All you need to do is find the cause of the short... If all the tants are removed then I'd start by checking any socket for bent or mangled pins, or anything in the sockets that might be causing a short. Also look closely at the front and back to …

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Re: AT pico psu.

Posted on 2022-02-20, 20:53

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It'd be three(?) extra components, but could maybe fudge it with a suitably debounced flip-flop running off +5SB, to make an ATX case switch act as a toggle on/off? It might need to switch via a FET to short PSON to GND, or might work directly off of the flip-flip output. I don't know what the …

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Re: Anyone know the polarity on the 3 leg tantalums in an IBM PS/2 type 8525 (Model 25). Color monitor/8086

Posted on 2022-02-20, 20:43

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Ok, so maybe the probes were touching originally. Have you been able to check the PSU connector yet? If you measure the resistance from J7 pin 2 to every other pin you should find shorts on pins 5,6,7,8 and not on any other pin. That will check there aren't any power-ground shorts. Pin 3 (+12V) …

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Re: Anyone know the polarity on the 3 leg tantalums in an IBM PS/2 type 8525 (Model 25). Color monitor/8086

Posted on 2022-02-20, 08:40

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

C84 was shorted when the cap was installed. I've pulled all 10 of them to do this last batch of testing. Also, C101 is the one that blew the top off, and of course the markings are on the destroyed side - but it's exactly the same size as 99 and 100 - the 25V ones are noticeably larger (see the 2nd …

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Re: Anyone know the polarity on the 3 leg tantalums in an IBM PS/2 type 8525 (Model 25). Color monitor/8086

Posted on 2022-02-19, 21:28

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I think I found a photo of the board, and it looks like C93 might be connected to Q2, which on the photo I've found is marked RIA or R1A, which could be an NPN transistor or a small adjustable voltage reference. If it's an NPN transistor then it might be used to connect the outer pin of C93 to …

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Re: Zida Tomato 6ABX with a bodge wire, advice needed.

Posted on 2022-02-19, 19:54

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Weird, it looks like a small value capacitor (might be pF, based on the pinkish colour) between R184 and CD37; CD37 probably goes between a power supply for the chipset and ground, and I guess the connection is to the ground side. So maybe someone wanted to slow down the rise/fall times of whatever …

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Re: two different socket 7 motherboard -no video on boot

Posted on 2022-02-19, 09:23

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Well, as Dionb said, the speed rating is a maximum, not a fixed requirement. So if the replacement works it's not because it's 66MHz, but something else (chip density, banking, ...). If we know more about what RAM you're trying to use, and which boards you've tested the RAM in, then we might be able …

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Re: Anyone know the polarity on the 3 leg tantalums in an IBM PS/2 type 8525 (Model 25). Color monitor/8086

Posted on 2022-02-19, 09:08

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Ok, if you're measuring resistances to the power connector then you need to check all the pins on the capacitor. The ones with centre connected to +5V might have their outers connected to Ground. The one with centre connected to Ground probably have their outers connected to -5V or -12V. The one …

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Re: Old Laptop Pentium 1 266 MMX with BIOS from Hell? Help Needed! >>SystemSoft BIOS for Intel 430 TX <<

Posted on 2022-02-18, 22:31

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Some BIOSes do weird things if there's a flat CMOS battery, so it might be worth putting a new one in. Thread about this laptop here: https://www.vogons.org/viewtopic.php?p=769898#p769898 and from there to here: https://forums.techguy.org/threads/solved-reformatting-problem.212988/post-1517284 …

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Re: LEONARD C 17924D board with CPU 286

Posted on 2022-02-18, 21:55

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

weedeewee wrote on 2022-02-18, 21:50: Just for starters, it's a 286 so 30 pin simms should be placed in pairs. Ah, that's an artifact of how I stitched the photos together which makes it look like there are 3 simms fitted, when there are 4 in the original photo. It's a parallax/perspective problem …

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Re: LEONARD C 17924D board with CPU 286

Posted on 2022-02-18, 21:24

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I'm pretty sure it is the board from a Leanord Elan. There are some small pictures here: https://www.old-computers.com/museum/photos.asp?t=1&c=1013&st=1 where you can see the cards in the case. It looks like the video was either Hercules or CGA, so maybe it'll depend on the graphics card that you're …

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Re: Old Laptop Pentium 1 266 MMX with BIOS from Hell? Help Needed! >>SystemSoft BIOS for Intel 430 TX <<

Posted on 2022-02-18, 18:06

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Even with no hard drive fitted? Weird. How can it know the size of disk that isn't connected? CMOS battery ok?

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Re: LEONARD C 17924D board with CPU 286

Posted on 2022-02-18, 18:04

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Looks to me like the silkscreen says Leanord, so maybe it's from something like this: https://www.old-computers.com/museum/computer.asp?st=1&c=1013 Even if right, doesn't really help much since there doesn't seem to be much information about it. [edit: hope you don't mind, but I've taken 3 of the …

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Re: Old Laptop Pentium 1 266 MMX with BIOS from Hell? Help Needed! >>SystemSoft BIOS for Intel 430 TX <<

Posted on 2022-02-18, 17:51

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Don't know if I can help with that. All I know is that on mine the main page of the BIOS shows "Hard Drive 0 = 2067 MB" and "Hard Drive 1 = CD-ROM". The IDE settings for both drives are set to enabled+PIO. Under boot sequence I have options for A: then C:, C:, A:, and CDROM then C:. I swapped the CD …

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Re: two different socket 7 motherboard -no video on boot

Posted on 2022-02-18, 11:47

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

> I get the lights on the keyboard afaik blinking keyboard means keyboard controller initialized = cpu is running Just on this, the keyboard will flash it's own lights when power is first applied (possibly when it's plugged in if the keyboard port is powered from 5VSB when using an ATX supply) and …

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Re: New clock gen for tyan s1564d

Posted on 2022-02-18, 10:41

by

by snufkin

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

R48 I got 4.7v on both sides which is what my atx2at shows on the 5v rail Sorry it took a while to get this to ya. Apologies. No worries, but that 4.7/5V bothers me a bit. We're fairly sure, based on the voltage you measured on C20 (goes to pin 1) and the resistance to ground of all the Vcc pins, …

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