Re: Tandon TM-100-2A floppy drive: head moves to track 39 (not 0!) and stays there

Posted on 2023-09-25, 18:29

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It would be best to remove the drive, power it externally and see what it does. I'm not familiar with Tandon FDDs but even the older models would self-seek to track zero on power-on. If yours doesn't do that it might a sign of a problem, though (due to age) it just might be too "stupid" and requires …

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Re: Lubricate FDD worm screw

Posted on 2023-09-25, 16:50

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Ok thanks for the pointers. It seems to be metal on metal by the way. Yes, but that's the spring on the top, bottom part is plastic. You need to be sure any grease (this is too exposed for oils) used here will not affect the plastic parts. Silicon grease is safe, PTFE is too but the additives (that …

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Re: Using old floppy disks?

Posted on 2023-09-25, 14:59

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I guess it is the right thread to ask this question ... ... so if a floppy is dirty, is there a way to clean it (without destroying it)? Any suggestions? Depends how dirty it is, with what, and how badly you need to read it. In some cases it might be worthwhile to carefully cut open the envelope, …

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Re: Setting Chinon FD-502 5.25 drive as B:

Posted on 2023-09-25, 13:52

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I don't know what the TERM jumper does but that floppy drive is old enough to have removable resistor pack, check if it is installed. Shouldn't really work at all without one but it's best to make sure. The drive should work as A: while jumpered as DS1 and sitting at the end of the cable, after the …

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Re: Cooling 386SX-16 in silent build

Posted on 2023-09-25, 13:32

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

386SX at 16MHz is probably an early Intel? These do run hotter than AMD chips and later low power Intel ones, but should not reach 75C or so, and this is still safe. That being said with zero airflow in the case everything will be cooking itself, slowly but surely, and while that will not kill any …

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Re: Lubricate FDD worm screw

Posted on 2023-09-25, 13:22

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hi, i just dissasembled an old floppy disk drive. It was owned by a heavy smoker. The worm screw was covered with black crusty goo, which I removed with Isopropanol. I guess i have to re-lubricate it now. What's best for that purpose? I have: - bicycle chain oil - WD 40 - Silicone based spray / oil …

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Reusing old HDDs

Posted on 2023-09-19, 11:33

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Long story short I have some old HDDs - as in MFM and early IDE and SCSI. I do have a few "modern" IDEs too but these in general either work or not, and if not they are just trash. The early ones on the other hand can be repaired, sometimes anyway, and I'm looking for any good tips on that. *) Loud …

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Re: 0Ah bad sector flag

Posted on 2023-09-09, 09:30

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

On phantom.sannata I was told that an MFM disk can skip bad sectors (they won't be visible at all!) No. MFM hard drive is a dumb device, it doesn't do anything on it's own and it will accept any bitstream format for the data. Even the later Seagate (and NEC?) HDDs that already have some servo-like …

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Re: 0Ah bad sector flag

Posted on 2023-09-08, 13:53

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You have to keep in mind that DOS kernel (and the programs) don't talk directly to hardware. There are some programs that work on lower level but these are usually special apps, and in case of IDE HDDs that would be either program from the manufacturer itself, or some that have obtained detailed …

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Re: 0Ah bad sector flag

Posted on 2023-09-08, 11:13

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Q1 - MHDD 3.0 when trying to remap (I don't know how he does it) just put a bad sector flag, like on MFM. Can anyone come across this? Q2 - Why do bad sector flags ignore format (trying to recover allocation unit) and scandisk (if you run it after the modified format / q)? What utilities generally …

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Re: CRT experience

Posted on 2023-08-11, 11:18

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Usually only early CRT monitors (mono, CGA) could be damaged by invalid H/V sync signals. And even some of these early ones have some form of protection against it (will not sync to signals too far out of usual range). That being said any experimenting is always somewhat risky, the older and tired …

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Re: 286 TwinHead TH4100 no post - I am stuck

Posted on 2023-08-10, 14:50

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You an ask KBC to reset the system, there might be an int 15h function for that as well (rather then doing direct I/O). I seem to recall DOS 3 had a program for easy rebooting the system from command line, but I might be confusing it with some non-PC machine...

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Re: 386DX upgrade to 486DLC

Posted on 2023-08-10, 14:47

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I have the motherboard shown in the photo . I set up jumpers JP1 and JP5 and run the TX486DLC processor but not working . Screen black and both processors get warm . Is the mobo working with its soldered 386DX? Figure out what jumpers JP1 and JP5 do, one (probably JP1) should be connected to the …

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Re: Hardware mod for L1 cache support on Cyrix 486DLC/SXL CPUs

Posted on 2023-08-09, 19:58

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That connection should work but play with the Fast A20 setting in BIOS to see if having it Enabled or Disabled breaks things. If it does then you can be pretty sure the signal works properly.

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Re: 286 TwinHead TH4100 no post - I am stuck

Posted on 2023-08-09, 19:55

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Usually a cap too big will slow the voltage raise too much and that causes problems. In your case missing cap (~0pF) was a problem. Well, nothing is stopping you from testing a bigger cap the. 510pF, or just add another 270 or so at the back of the existing one for testing purposes and see what that …

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Re: 5.25" drive wont move head

Posted on 2023-08-09, 18:24

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

oldcomplover wrote on 2023-08-09, 15:51: no head movement Can you move the sled by hand with the drive unpowered? It should move easily when pushed with one finger.

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Re: What's up with my CRT, and, are these contemporary Creative speakers even shielded?

Posted on 2023-08-09, 18:19

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I also took a closer picture of the "ghosting" issue I'm getting. This is with a completely different computer and VGA cable than I used in the first picture, and it's still having the issue. Different doesn't mean good. A decent VGA cable should be some 9-10 mm in diameter, reason being the RGB …

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Re: 286 TwinHead TH4100 no post - I am stuck

Posted on 2023-08-09, 18:10

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That cap is there only to somewhat debounce the switch, not critical - and while it will also affect POWER GOOD signal, the time constant of 270 pF and 470 Ohm is about 127 ns if my napkin math is corrrect. That should not matter for POWER GOOD if the chipset was designed correctly and it has …

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Re: 286 TwinHead TH4100 no post - I am stuck

Posted on 2023-08-09, 14:44

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Basically the button is connected like that Check again because I'm pretty sure that diode should be connected backwards. You might want to try and replace this diode, assuming it's a standard silicon like 1N4148, with something Schottky. Reason being it'll have lower voltage drop and drive the …

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Re: Hardware mod for L1 cache support on Cyrix 486DLC/SXL CPUs

Posted on 2023-08-09, 13:52

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

So, new discovery: I changed up my barb setup to include -a, -m, and -r- (to take advantage of the fact that I know the A20 line works). Speedsys doesn't work this way either! so if -m and -r- are both enabled, speedsys chokes. Interestingly, it must cache the first ISA scan it does the first time …

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