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Thread: Thinkpad 750c no LCD ouput, 20288K OK on VGA... ideas?

  1. #1

    Default Thinkpad 750c no LCD ouput, 20288K OK on VGA... ideas?

    I have a 750C a buddy of mine gave me years ago... after removing the NiCD pack it powers up and displays 20288K OK on the VGA port does similar if I remove the 16MB kingston ram card just drops the tested memory by 16MB. I also removed everything HD, FDD, Extra RAM and the battery... and it does the same thing. On power up it checks the FDD, and the HDD spins up and seeks a bit also the mem test doesn't seem to count up like it does on the Compaq LTE I have it just shows the amount.

    Also note that the case is very much worse for wear but the internals look clean enough.

    The LCD doesn't flicker or anything always dark.

    I have a copy of the http://greyghost.mooo.com/pccbbs/mobiles/sytps143.exe which is apparently the latest Reference Diskette ? I'm not sure how that works though do you just drop that EXE on a diskette or do you have to do something else with it?

    Bear in mind I was a kid running DOS on an 5150 IBM PC so there is some familiarity but ... I only really understand Win95 and up and Linux/Solaris decently otherwise alot of the machine specifics from the DOS days are lost on me ha!

  2. #2
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    Reference disks are for PS/2 machines which this is not.

    Hold the F1 key when you turn the unit on to get into the BIOS and then do diagnostics. You can then make sure the time and setup are correct and the boot order of the machine.
    What I collect: 68K/Early PPC Mac, DOS/Win 3.1 era machines, Amiga/ST, C64/128
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    Try this: take a flashlight and put it up to the screen, like flush to the screen and look. If you see the RAM count/BIOS screen, the bulb or inverter is dead. If you see nothing, either the LCD or the cable is dead.
    Wanted: Any old clunky 286-P1 machine that has some kind of working battery or replaceable with off the shelf parts. Preferred: 10+lbs 386 machines.

  4. #4

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    Quote Originally Posted by Unknown_K View Post
    Reference disks are for PS/2 machines which this is not.

    Hold the F1 key when you turn the unit on to get into the BIOS and then do diagnostics. You can then make sure the time and setup are correct and the boot order of the machine.
    Already tried that no noticeable effect. Bascially hold down F1 while powering up... did that and it didn't do any different. Also, Once the 20288k OK shows up on my VGA monitor... the cursor stays just below the text rather than going to the upper right as it should(I was reading this last night so I could be remembering incorrectly).

    OK, so a Reference disk would only exist for ie the NX-40 up through P75 I guess. I guess the program I have there is just a BIOS flasher then?

    Also it seems to have 2 detachable batteries internally both of which are thankfully intact... I probably need to test those next I guess.

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    Batteries for a laptop that old are pretty much junk.
    What I collect: 68K/Early PPC Mac, DOS/Win 3.1 era machines, Amiga/ST, C64/128
    Nubus/ISA/VLB/MCA/EISA cards of all types
    Boxed apps and games for the above systems
    Analog video capture cards/software and complete systems

  6. #6

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    Is the LCD plugged in properly inside? haha...
    I had a Toshiba that the lid sensor wasn't connected so it always thought it was closed. Other than that without any EE skills it could be anything between the GPU and the LCD PCB.

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    Quote Originally Posted by Unknown_K View Post
    Batteries for a laptop that old are pretty much junk.
    Also, these are VERY SMART BATTERIES. They will refuse to boot if the PRAM in the battery goes dead, which it obviously has. This isn't your run of the mill 386-battery with 8-D cell NiCD in a black shrink tube and a thermistor. Also, don't even consider rebuilding, the battery is one hell of a tank.
    Wanted: Any old clunky 286-P1 machine that has some kind of working battery or replaceable with off the shelf parts. Preferred: 10+lbs 386 machines.

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    Quote Originally Posted by twistedpneumatic View Post
    Try this: take a flashlight and put it up to the screen, like flush to the screen and look. If you see the RAM count/BIOS screen, the bulb or inverter is dead. If you see nothing, either the LCD or the cable is dead.
    I second this; a dead backlight was my first guess as well.

  9. #9

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    Just did the flashlight check (should have already thought to do this honestly thanks for the tip).

    Backlight/Inverter is dead.

    The screen has the same 20288k OK on the screen and nothing else same as the VGA though so... there are other issues it seems?

    I pulled the main NiMH battery... it powers up without but but doesn't get past POST it seems though it isn't beep coding or anything like that.

    @Caleb no EE skills, what you mean I'm a computer engineer... I mostly do micro controller stuff though. I probably could rebuild the NiMh if I wanted perhaps even with a Lion pack and some fancy conversion to make it think it was the NiMH but I have too many little projects already ha! Some of these old smart battery packs were probably designed this way so they could sell different battey chemistries in the same format potentially mostly SLA and NiMH at the time and maybe LION a little later on... though that has largely went the way of the dodo.

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    Honestly, just rebuild it and externally charge it. I make batteries that I charge externally. Use could use some AA batteries. I could see if I could create something.
    Wanted: Any old clunky 286-P1 machine that has some kind of working battery or replaceable with off the shelf parts. Preferred: 10+lbs 386 machines.

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