Re: Beep during formatting a floppy disk

Posted on 2023-12-20, 10:54

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I found out that the Delayed Transaction must be disabled. When it is enabled I get the beep after format A:. It also turned out that the problem with the Mozart soundcard was over. That is very odd. I wonder if there might be a bug in the BIOS code, and the floppy routine is somehow tripping it …

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Re: Beep during formatting a floppy disk

Posted on 2023-12-19, 14:35

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The beep is not coming when I do format a: under Windows 98 SE. I will do some of the other tests. Win95 and later systems do not use BIOS to access floppy drives in favour of 32-bit protected mode code, and that would explain why there are no beeps. The boot sector protection code is not being …

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Re: EEPROM AT93C66 content in a 93LC46

Posted on 2023-12-17, 17:39

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You can't fit 512 bytes into 128 byte part. Not only there isn't enough memory space but the addressing is different too - in 8-bit mode the 93C66 needs 9 bits of address whereas 93C46 only needs 7. As far as organization is concerned (8-bit vs 16-bit) the internal bit/byte order is not specified. …

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Re: Zip Drive maintenance suggestions?

Posted on 2023-12-15, 12:34

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

AFAIK the problem with these ZIP drives is the head gets ripped off by residue buildup, and that comes from degraded media that starts shedding the magnetic material coating. Louder operation is usually due to the friction between media and the head, could be just this particular head+floppy is more …

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Re: Beep during formatting a floppy disk

Posted on 2023-12-15, 12:13

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Some sort of BIOS protection of boot sector perhaps? There should be a menu entry to disable it.

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Re: 486 motherboard troubleshooting log (DTK PKM-0037S)

Posted on 2023-12-12, 14:15

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Questions Do these symptoms make sense? There's clearly activity and the CPU is doing something. Could a cracked or broken ISA trace as suggested by Trashbytes break the whole ISA bus? Would you expect the system behavior to change with no RAM? I figured it would just hang and beep angrily with no …

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Re: Better understanding barrel battery charging circuit

Posted on 2023-12-07, 11:18

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

4) You can connect CR2032 between pins 3 and 4, that way you will not need to modify the mobo in any way. That would make the clock always powered by the battery, even when the system was powered on. True, but that's how a lot of modern RTCs work anyway. The only problem is older chips that have …

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Re: Better understanding barrel battery charging circuit

Posted on 2023-12-06, 13:55

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

3) NiCd chemistry can take 1C charging current. This would be half so safe, and it would still need 2h (plus some extra due to charging not being 100% efficient) to fully charge the battery, not that unusual. Though usually, with daily use, you would not need that long for full recharge. This is a …

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Re: Switching on old computers after long period of being switched off

Posted on 2023-12-02, 20:30

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

If this is going to be some sort of museum or exhibition where these machines are going to be powered, even if only from time to time, it would be best to keep a logbook for each (at least for each group). Save yourself and others the trouble of figuring out what has been tested, and when, or …

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Re: Switching on old computers after long period of being switched off

Posted on 2023-12-02, 18:51

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I’m hesitant in applying the Capacitor reforming using a variac. There is no need to reform electrolytic caps in modern equipment. It can be done but there is usually little point in doing so. Any transformer based equipment will only have low-voltage caps. Now the really old and power-hungry stuff …

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Re: PC Chips M326 v5.3 386/40 motherboard with both surface mount 386/40 and 386 socket

Posted on 2023-12-01, 14:15

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The 2 active CPUs increase the load on the chipset pins. All pins (input AND output) have a current rating which, if exceeded, can damage that pin. Thus, by not disabling the onboard CPU, the chipset would drive 2 CPUs when it was designed for only 1. That certainly results in burning chipset …

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Re: General old 3.5 floppy weirdness (Track 0 bad error)

Posted on 2023-11-25, 00:52

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Grzyb, depending on DOS version you might need to use /C along /U to recover clusters already marked as bad. IIRC this is needed in 6.x but not 5.0 which does not know /C. DOS 3.x and prior didn't even have /U, format was always a format and not read test plus FAT wipe.

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Re: General old 3.5 floppy weirdness (Track 0 bad error)

Posted on 2023-11-24, 22:41

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

DOS is a pretty stupid OS, and when it tries to be "smart" it's even worse. Track 0 bad can be caused by a few things but not all of them are actual media defects. Wrong format already present on the floppy (even when using /U option) can cause that too, as well as some glitches and bad sector …

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Re: Advice regarding RAM issue in Slot 1 motherboard

Posted on 2023-11-24, 14:39

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

This sums up to 1.5Gb of max RAM. In theory. Not all combinations will be supported, plus there's the cache size and configuration (as well as particular chipset type) that might limit the amount of usable RAM. As for DIMMs, keep in mind there are single and multi-rank modules. Chipset might not be …

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Re: XT-IDE with a 3com 3c509tp

Posted on 2023-11-23, 09:26

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

AT28C64 or AT28C64B? There is a difference. Not all ETH chips guarantee that unused address lines will always be held high (RTL8019A does) plus the 3Com setup programs insists on testing the EPROM before accepting config changes. Use B parts or even EPROMs instead of EEPROMs. If using bigger …

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Re: 5.25" Floppy Drive - Y-E DATA

Posted on 2023-11-03, 11:07

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I said QD, not HD. To the best of my knowledge the magnetic coercivity of QD and DD media is the exact same I read you right but for some reason I misremembered coercivity for QD media. I can't find the source now (I don't trust Wiki) and my claim that HD media would be a better fit was also based …

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Re: problem with CRT

Posted on 2023-10-29, 17:57

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Series cap like that you mostly find on low end stuff like (smaller) TVs, monitors (and large TVs) tend to have direct coupling for best linearity and framerate performance. I see. My experience with "modern" color CRT SVGAs is limited. The only things I've had to deal with so far was CRT gun …

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Re: 386SX Motherboard Won't POST, AMI BIOS Code AA

Posted on 2023-10-29, 17:49

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

What should I poke at to find the issue I wonder? Assume nothing about the SIMM bank setup. Try 2 sticks in each socket pair. Use 9-chip sticks if you have them, the 3-chip ones are often causing parity issues due to refresh or timing issues. Connect reset switch and reset the mobo via the switch, …

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Re: problem with CRT

Posted on 2023-10-28, 18:09

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It could be a cap issue, I haven't worked on many color CRT monitors but usually there is an electrolytic cap in series with the deflection coil. It's there to prevent destruction of the driving transistor/IC in the unlikely event the frequency goes so low that the pulse saturates the coil. If that …

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Re: [SOLVED] Malfunctioning floppy drive

Posted on 2023-10-27, 10:12

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Cooking oil and pig grease. Start looking for a replacement drive, this one will fail sometime next year and this time will require disassembly to get it clean and working again.

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