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Type: Posts; User: RetroSpector78

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  1. Took another look at it and noticed that the 2...

    Took another look at it and noticed that the 2 terminals coming out of the microswitch don't have continuity when I toggle the switch. So this might be the culprit

    61874
  2. That's the microswitch next to the drive motor...

    That's the microswitch next to the drive motor that is pressed in when the head moves all the way back I guess ? I did spot that one and it did "sound" ok when I clicked it, but will check that one....
  3. Most XTs seem to do a seek at startup, and i am...

    Most XTs seem to do a seek at startup, and i am using the standard IBM floppy controller.

    Most of what DOS needs to start reading a disk is on track zero. So if it can't read at all, it may just...
  4. IBM PC XT 5160 Tandon TM100-2 issue

    Hi,

    I have an IBM PC XT with a Tandon TM100-2 floppy drive that is having some issues.
    C43 blew upon startup so I replaced that one, and I found another cap that was bad according to my ESR...
  5. I measured the hsync / vsync pins on the...

    I measured the hsync / vsync pins on the videocard (without the monitor attached).
    And the DIP switches on the motherboard don't seem to have an impact on the horizontal / vertical sync output on...
  6. I suppose I can check the h-sync frequency on the...

    I suppose I can check the h-sync frequency on the 9pin d-sub connector to see what the card is outputting under various conditions (without hooking up a monitor) ?
    And regarding the MCG2502 chip on...
  7. I'm afraid the fuse still works as I see a green...

    I'm afraid the fuse still works as I see a green ghost like image appearing when I connect / disconnect power to the display. But nothing after that.
    Guess I'll have to get over my fear of working...
  8. Case of IBM 5151 killed by bad video signals ? Or was it already broken ?

    Hi,

    I have an IBM XT with an Auto Switching Dual Display Adapter (Model 2502 Revision A1)

    According to http://vgamuseum.info/index.php/companies/item/504-ram-mcg2502 this appears to be a...
  9. Philips P3120 with old Western Digital xt-ide hard drive

    I have 2 Philips P3120 computers (XT class machines) here both with a Western Digital WD-93028-X 20MB hard drive.
    ...
  10. Everything is integrated on the mainboard (I/O...

    Everything is integrated on the mainboard (I/O ports, floppy , hard drive, video). So minimal config would only be disconnecting the floppy and hard drive. But also there I have the reset issue on a...
  11. The CPU is a 100-pin plastic QFP package soldered...

    The CPU is a 100-pin plastic QFP package soldered to the mainboard. No socket.
    A lot of people say these random reboots are often PSU / capacitor related. But I can also imagine like you say that...
  12. Any idea where I find this reet line ? Would it...

    Any idea where I find this reet line ? Would it be exposed on the power connector going into the mainboard ? (there is no reset button on the PC).
  13. 386 computer constantly resets when "running cold"

    Hi,

    I have an Olivetti 386sx machine that didn't want to start.


    I've replaced all polymer SMD caps on the mainboard (they were leaking) with standard electrolytic caps. (replacement parts...
  14. Replies
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    330

    I also asked the question here :...

    I also asked the question here : https://electronics.stackexchange.com/questions/490260/what-is-causing-a-voltage-drop-on-the-5v-power-rail-on-this-bench-setup

    Issue is caused by the series...
  15. Replies
    4
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    330

    The test points I am using map to directly pin B1...

    The test points I am using map to directly pin B1 and B29 (GND) and pin B3 and B29 (+5v) on the isa slot

    - So bench supply is connected to B1 (GND) and B3 (+5v)
    - Multimeter is checking voltage...
  16. Replies
    4
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    330

    MDA videocard power consumption

    I have an old MDA videocard that I am trying to debug.

    I've hooked it up to my lab bench PSU and hooked up 5V (the card has a header that maps to the ISA pins so it is easy to wire jumper cables...
  17. There is a 18.432 crystal and a 16.254 crystal. ...

    There is a 18.432 crystal and a 16.254 crystal.

    Without schematics it's not the easiest thing to track, but I have found an electrical path from the 16.254 crystal to the CLK pin (through various...
  18. What is an XCO ? The 5V line appears to be...

    What is an XCO ?

    The 5V line appears to be fine ... Tested it on a 5150 and 5162 (both computers running without issues and run happily with my IBM MDA card (that card is showing the 1.80633 MHz...
  19. MDA Card MC6845 dot character clock frequency

    I have an old Tseng UltraPAK MDA card with the Motorola MC6845 chip (as also used by the IBM MDA card and CGA card).

    The card is not working properly (1 long beep followed by 2 short beeps). It...
  20. Replies
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    2,280

    Does the capacitance make a big difference when...

    Does the capacitance make a big difference when replacing those Rifa caps ?
    I have 2 PSUs here rom old IBM machines with a blown RIFA cap, one has a 470 nF, the other a 100 nF.

    Is it "safe" to...
  21. I figured the memory chips might also be...

    I figured the memory chips might also be considered more error prone than others, so I removed those from the Tseng Labs Ultra Pak card and put them in another MDA card (that had sockets for the...
  22. But to get back to the original question : Are...

    But to get back to the original question :

    Are there some common components on these old videocards that are more error prone and more likely to fail than others ?
    What would be the best place to...
  23. I'm guessing it's one of those cards thats...

    I'm guessing it's one of those cards thats combines serial / parallel / video / realtime clock.
  24. Video card and original motherboard got...

    Video card and original motherboard got separated. The videocard contained the battery. Currently testing with a clean IBM machine. PC is working fine so full focus is on the videocard.
  25. I know , the things I did + questions I asked are...

    I know , the things I did + questions I asked are all related to the videocard. Sorry if this was not clear.
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