Re: Schneider D486 20 - fixing a weird and broken PSU

Posted on 2024-02-24, 22:37

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Any idea how to test a -12V regulator? The only true test for any voltage regulator is to load it and measure the output (voltage, ripple). That being said it's rare for these things to go bad. I think it would be safe to remove it from PSU entirely if you suspect it's shorting the rail and …

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Re: Schneider D486 20 - fixing a weird and broken PSU

Posted on 2024-02-24, 19:02

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

actually I'm not sure. When inspecting the pcb I did checkfor continuity and everything was fine. To be sure, I added a wire between the solderjoints. On the other side of the board are I beleive an inductor, -12V regulator and an potentiometer. Desolder all nearby electrolytic capacitors, this is …

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Re: Epson Equity I (IBM XT Clone) - Floppy Disks not recognized

Posted on 2024-02-24, 12:36

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

When I moved the heads out of position of track 0, -> no reaction as well. Most floppy drives will auto-seek to track zero on power-on. Though not all, some really old ones don't do that. First, there is some dust there, perhaps enough have gathered in the slot of the light barrier - try blowing …

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Re: Smoke on 386 Motherboard !!!

Posted on 2024-02-23, 17:49

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

megatron-uk wrote on 2024-02-23, 17:26: unlike normal electrolytic capacitors which usually don't go bang You haven't tried hard enough 😀 They do go bang too, and tend to leave quite a mess when they do. Though it is very rare for low voltage electrolytics to go bang with nominal voltage applied.

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Re: Win98 PC to Windows 11 PC Internet Connection Sharing

Posted on 2024-02-23, 16:13

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Checking ipconfig on Win98, it does assign an address and subnet mask, but not a default gateway. Where would I set the TCP stack to use DHCP (or at least check if it's set or not)? IIRC you need to double-click on the TCP/IP protocol component in Network details window. If the IP you are seeing is …

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Re: PLS Help! 386 faulty unidentified motherboard

Posted on 2024-02-23, 16:05

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It's cheap but you want ALS245 and not anything else. ACT might be a good substitute but the more common HCT can be too slow or have to low drive for all these ISA slots. Also it should be safe-ish to try and piggy-back the original chip with a brand new one of the same series. I would not expect …

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Re: Hard drive setup on 386

Posted on 2024-02-23, 15:59

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The BIOS can actually be set to 40 GB with some unrealistic settings. It is mainly those LBA errors that concern me. I'll mess with it further today. It could even be that the drive doesn't support CHS, at all. It's my last 40 GB drive but there's no shortage of 80 GB drives in my drawer and one of …

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Re: Hard drive setup on 386

Posted on 2024-02-23, 15:55

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

ATA drives without auto-park do exist. Many early ATA drives use a stepper, and stepper usually means no auto-park. See eg. WD 95044-A That's just another reason to avoid 93044/95044 models, apparently there's nothing good about these (slow, unreliable). Seagate made plenty of stepper motor HDDs, …

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Re: Win98 PC to Windows 11 PC Internet Connection Sharing

Posted on 2024-02-23, 00:14

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Windows sucks as a router, always did and probably always will. That being said I think it should "just work" if the Win98 TCP stack is set to use DHCP. Did you check if it's getting IP assigned at all?

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Re: Hard drive setup on 386

Posted on 2024-02-23, 00:05

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Though I've still not figured it out, what in the world is "PRE-COMP" and "LAND-ZONE"? These two settings only apply to MFM/RLL drives. ATA ones, no matter how old, do precompensation internally and I've yet to see one without auto-park so landing zone is also irrelevant. As for the error, is the …

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Re: PLS Help! 386 faulty unidentified motherboard

Posted on 2024-02-22, 22:15

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Looks like 386E, but mine lacks the jumpers 4 & 5, and has one 8bit slot instead of two. Good eye! But I've seen many mobos where the 8-bit slot was just a standard 16-bit one, but the edge connector was shorter. One could replace it with a standard one to gain another full size ISA slot. I think …

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Re: PLS Help! 386 faulty unidentified motherboard

Posted on 2024-02-22, 17:58

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Unfortunately there are some issues and the biggest mystery so far (but not a straight issue per se ) is that I have no idea what make and model this motherboard might be... Looks to be 386E-25MHz: https://theretroweb.com/motherboards/s/unknown-386e-25mhz Seems like it's very similar to 386WB I …

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Re: 286 Motherboard does not work . CMOS inoperational. System halted.

Posted on 2024-02-22, 17:16

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

With the resistor I got the same error. It was worth a try, a pity it didn't do anything. Since you are now checking all the connections please make sure the data bus (pins with D0 to D7) on the RTC/NVRAM chip are connected to one of the big chipset parts on the mobo. I would also assume that both …

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Re: AT/LANTIC DP83905 broken EPROM

Posted on 2024-02-22, 17:08

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

When both \WE and \CE go low AT28Cxxx disconnects its internal output buffers from data pins and starts to read from them instead of writing . Right, I didn't consider that. That means the /WE pin on the EEPROM must not be driven low if you need valid ouput for A14=0 (without messing about with the …

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Re: AT/LANTIC DP83905 broken EPROM

Posted on 2024-02-22, 14:00

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

For 28-series EPROM to work it's necessary to disconnect A14 line of EPROM from ISA and tie it to +5V. This shouldn't be needed on 28C256. In the datasheet look for "Software Data Protection". Not sure what EEPROM programmer you have but most should be capable of turning this option on/off. When …

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Re: Mysterious earlier 386 motherboard VLSI

Posted on 2024-02-22, 00:29

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Iam thinking its an combi 286 / 386 boards? Never have seen this.. Or perhaps 80287 could be used. 386DX can work with 80287 coprocessor, the reason is Intel was late with 387 (and they knew it) so they opted to add support for 287 to allow the early adopters to use something at least. But I would …

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Re: RLL ST-1105R data recovery

Posted on 2024-02-21, 23:10

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Did you mean ST1106R instead of 1105? Because I can't find any info on 1105 model whatsoever. I'd never considered the Greaseweazle. I've seen them mentioned for quite a while but have no experience with them. Short version is the device is meant for low-level reading, and writing, of floppies. Much …

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Re: M571 Motherboard no pc speaker sound

Posted on 2024-02-21, 15:52

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Well, I was rather hoping the PC speaker output would be handled by something ISA-related, like the UM8670F chip. Or at least I think this one is some sort of Super I/O and ISA bridge, there isn't much info about it. But if the problem is with the main BGA chip then I'd say you are out of luck. One …

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Re: M571 Motherboard no pc speaker sound

Posted on 2024-02-21, 14:26

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

If you have a meter with a good, fast beep on short function you could try to find out where the signal comes from by sweeping over the chipset pins with the meter probe. I did a lot of that for various mobos and never damaged anything. With the 4k7 resistor in there I don't see how any decent …

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Re: M571 Motherboard no pc speaker sound

Posted on 2024-02-21, 12:54

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I guess the best place to put the 1k resistor and the LED would be before the 4k7 resistor? Since you located that resistor, you can connect the LED directly to it and skip the 1k resistor (but that will require temporary removal of the transistor). Keeping it is safer (in case of picking a wrong …

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