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Thread: Toshiba T1200 schematic

  1. #1

    Default Toshiba T1200 schematic

    Pondering picking up a local T1200.

    I've seen the great into at minus zero, but did not see a schematic.

    Anyone know if a schematic is available? I suspect this one may have a few issues.

    Thx

  2. #2

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    I've just repaired one of these, the PSU board have around 5 capacitors that leak and cause powering issues.
    It's an easy repair if you pick one up and it won't power up. There are also 2 NiCd backup batteries inside the unit
    (1 at the rear and another under the keyboard) check them first before anything. Nice little machine and great for
    some Retro DOS stuff. Lots of info on the net for repairs and in this forum.

  3. #3

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    IMO, I'd pass on it. It's not always just the capacitors that make them fail to power up. I got one and the caps were leaking really badly on the internal PSU, so I thought it was going to be an easy fix, just replace the caps. Replaced the caps and still nothing. Dead as can be. Have no idea what makes these Toshibas so flakey and unreliable, but from what I heard one person say, they were not even reliable back in the '90s when the machines weren't all that old. The gray AC-powered units like the T3100e are much, much better. I have never had any issues from those. But the T1100, T1200, T1000 are all crap. Shame, because they are really cool otherwise.

    Now if we can figure out what's making these fail, we may be able to revive them, but until then, they are on my list of computers to avoid.
    Compaq - “It simply works better”

  4. #4

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    thanks for the feedback. to buy a machine that can't be shown to power up at all (in this case no PSU) and then to assume it can be fixed reasonably easily, .. is a stretch. Too much for me. I did have good luck with a Zenith Z-171 that I bought with knowledge if it would boot or not. Feel like I got lucky once. Plus, I know I would have to get an XT-CF going for this box, since almost certainly the disk will be Kaput.

  5. #5

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    Quote Originally Posted by Twospruces View Post
    thanks for the feedback. to buy a machine that can't be shown to power up at all (in this case no PSU) and then to assume it can be fixed reasonably easily, .. is a stretch. Too much for me. I did have good luck with a Zenith Z-171 that I bought with knowledge if it would boot or not. Feel like I got lucky once. Plus, I know I would have to get an XT-CF going for this box, since almost certainly the disk will be Kaput.
    No problem! Nice you got a Z-171! Those are super cool. I have had great luck with Zenith computers. I bought an untested Z-181 several months ago and it fired right up when I plugged it in. Didn’t have to turn a screw on it (except for when I upgraded the CPU).
    Compaq - “It simply works better”

  6. #6

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    Quote Originally Posted by compaqportableplus View Post
    IMO, I'd pass on it. It's not always just the capacitors that make them fail to power up. I got one and the caps were leaking really badly on the internal PSU, so I thought it was going to be an easy fix, just replace the caps. Replaced the caps and still nothing. Dead as can be. Have no idea what makes these Toshibas so flakey and unreliable, but from what I heard one person say, they were not even reliable back in the '90s when the machines weren't all that old. The gray AC-powered units like the T3100e are much, much better. I have never had any issues from those. But the T1100, T1200, T1000 are all crap. Shame, because they are really cool otherwise.

    Now if we can figure out what's making these fail, we may be able to revive them, but until then, they are on my list of computers to avoid.
    I'd have to disagree with you about the Toshiba's being unreliable, Toshiba produced and still do produce the most reliable and long lasting laptops, not to mention the chips and components they also make. I would have to say they are equal to Compaq in design and construction, the components are always top quality and made in Japan. As for the repairing the old and fualty laptops, it is no more a gamble than repairing anything electronic that is more than 30 years old. Yes, not always the caps but 80% of the time it is the caps, the other 20% being leaking batteries, bad/corrupt CMOS/BIOS chips, power diodes/transistors, poor connections/solder joints and fuses.

    You do know that some of the T1000 series will not power up or boot without a working internal battery. I've repaired a couple of T1000's and T1200's and both will not power on if the internal battery is bad. It's just a case of re-wiring the power cables on these units. From my experience the caps are the only cause of power failures on these systems.

    Powering up any vintage laptop or computer system without some form of current limiting power supply may cause much more damage than there actually is. So the very
    first thing to do is inspect the board visually and with a meter, then replace all the caps that are connected to high power tracks before powering up. Capacitors cannot reliably be tested whilst in circuit and must be removed or at least one of the legs lifted and tested in place. I see many videos of capacitors being tested in circuit with those cheap component testers and this is just not the correct way to test components. Those testers cannot mimick the operating conditions of large power caps so it is always best to replace them even if they look fine.

    Go have a browse at the Toshiba pages here https://oldcrap.org/ for some excellent Toshiba T1000/T1200 info.
    All the info is meticulously presented with links to repair manuals, setup files, ROM's and internal photos.
    Last edited by rimmeruk; September 20th, 2020 at 10:35 AM.

  7. #7

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    Quote Originally Posted by compaqportableplus View Post
    No problem! Nice you got a Z-171! Those are super cool. I have had great luck with Zenith computers. I bought an untested Z-181 several months ago and it fired right up when I plugged it in. Didn’t have to turn a screw on it (except for when I upgraded the CPU).
    Zenith make unusal systems and are usually reliable systems, but they also use their own proprietary power supply adpaters and connecters. I've had to replace the power plugs on some zenith's to standard 2.5mm DC plugs as the power adapters are hard to find.

  8. #8

    Default

    Quote Originally Posted by rimmeruk View Post
    I'd have to disagree with you about the Toshiba's being unreliable, Toshiba produced and still do produce the most reliable and long lasting laptops. I would have to say they are equal to Compaq in design and construction, the components are always top quality and made in Japan. As for the repairing the old and fualty laptops, it is no more a gamble than repairing anything electronic that is more than 30 years old. Yes, not always the caps but 80% of the time it is the caps, the other 20% being leaking batteries, bad/corrupt CMOS/BIOS chips and bad solder joints.

    You do know that some of the T1000 series will not power up or boot without a working internal battery. I've repaired a couple of T1000's and T1200's and both will not power on if the internal battery is bad. It's just a case of re-wiring the power cables on these units. From my experience the caps are the only cause of power failures on these systems.

    Go have a browse at the Toshiba pages here https://oldcrap.org/ for some excellent Toshiba T1000/T1200 info.
    All the info is meticulously presented with links to repair manuals, setup files, ROM's and internal photos.

    I stand by what I said above. I have bought 2 completely different models (T1200 and T1000LE), recapped them and still dead with the “blinking red light of doom” that these Toshibas get. And yes, I tried powering both machines through the battery contacts as well. Didn’t help.


    However, I have bought 6 Compaq SLTs and every single one fired up on the first try. I also just got a Texas Instruments TravelMate LT286/12, which also fired right up without fuss.


    Yes, the Toshibas are good quality units, but their power supplies have a design flaw somewhere, and as I said, I won’t drop another penny into one unless someone can figure out why they are so temperamental.


    Zeniths do use a center-negative power supply, which is odd, but they usually work with little-to-no fuss.
    Compaq - “It simply works better”

  9. #9

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    The blinking red light is the battery charging circuit protection, the battery needs to be functional and chargeble along with the DC input power.
    If you have missed any caps on the board then you may also get the blinking red light. You could say anything which does not power on
    has a design flaw, I wouldn't say it was a flaw as it works with all the correct capacitors and batteries replaced.

    I've repaired 2 units with the blinking red light and the blinking led that you are talking has other conditions in which it blinks to show
    the diagnostic code. There is also an led code output on the LPT port which are all listed in the repair manual with the correct procedure
    to remedy the fault. I guess that you did not use an LPT diagnostic connector on the LPT port as the blinking red led suggests there was a fault
    code available and the error could be something other than the battery or power.

    You see, almost all Toshiba laptops from that era had an integrated diagnostic circuit and ROM which allowed the use of a LPT dongle to diagnose
    any faults with the system through the printer port (of course you'd be stuck if the LPT port failed). These dongles are easily made with just a handful
    of leds and some wiring. I have used the for all sorts of diagnostics on Toshiba's and you can even reset the CMOS chip and any registered passwords.
    If you are serious about repairing and restoring vintage computers, you would have one of these dongles.

    I guess you were lucky to find 6 working laptops, that's not to say the non working Toshiba's had design flaws is it.
    Thinking about it, you could say that all electronics from that era had design flaws when you compare them to the advancement
    in electronics today

    I'm only trying to point out that you may have missed something else when diagnosing the board and you may have focused all your
    attention to the power supply when the fault could of been something as simple as a jumper switch or corrupt CMOS memory.

    Sorry for the lenghty post, but I always like to detail my response with as much information backing up my statements rather than
    one-shot comments.

    What has it got to do with a Zenith center-negative plug ?
    Last edited by rimmeruk; September 20th, 2020 at 01:58 PM.

  10. #10

    Default Toshiba T1200 LED Error Codes

    Printer Port LED Check
    The printer port LED informs the IRT program status and
    error status as a hexadecimal value after power on the
    system. Connect the printer port LED to the printer port.
    After power on, read the LED status from left to right.
    If the final LED status is FFH, perform the PROCEDURE 3.
    If the final LED status matches any of the error status code
    or normal status code value in the table 2-1, replace the
    system board.

    File No. 960-018
    Table 2-1 Normal status and error status
    of the printer port LEO (1/2)
    Normal Error
    status status MeaninJt Process
    01H 81H CPU test 1 (flaq test) Halt
    02H 82H KBIC IBF/OBF test, Halt
    Video initialization
    03H 83H KBIC (KBC) IBF test Halt
    (OAAH command)
    04H 84H KBIC (KBC) OBF test Halt
    (SSH check)
    OSH Reserved
    06H LSI initialization Continue
    (OMA PIT, PIC RTC)
    07H 87H CPU test 2 (reqisters) Halt
    08H RTC initialization Continue
    (reqister B)
    09H 89H ROM checksum test ( 64KB) Halt
    OAH 8AH Video initialization Halt
    OBH Reserved
    OCH Reserved
    OOH 80H PIT ch2 test and its Halt
    initialization
    OEH CMOS time/date test Continue
    OFH 8FH CMOS RAM test Halt
    10H 90H OMA chO test Halt
    11H 91H OMA ch1 test Halt
    12H 92H OMA paqe reqister test Halt
    13H 93H KBSC test and Halt
    its initialization
    14H 94H Memory refresh test Halt
    1SH 9SH 1st 64KB RAM test Halt
    16H Interrupt vector setup Continue
    17H 97H Video option test Halt
    18H 98H V-RAM test Halt
    19H 99H PIC ch1 test 3 beeps
    continue
    ERROR INTERRUPT CONTROLLER #1 messag·e appears.
    1AH 9AH PIC ch2 test 3 beeps
    continue
    ERROR INTERRUPT CONTROLLER #2 messaqe appears.
    1BH 9BH CMOS battery test 1 beep
    key wait
    ***
    Error in CMOS. Bad Battery
    ***
    Check system. Then press any key
    messaqe appears.
    1CH Reserved Continue
    10H 90H Setup RAM size from cr-10S C o n t i n ~ . . : . e
    (413H)
    1EH 9EH Size conventional RAM Continue
    2-17
    File No. 960-018
    Normal
    status
    1FH
    20H
    21H
    22H
    Table 2-1 Normal status and error status
    of the printer port LED (2/2)
    Error
    status Meaning
    9FH Conventional RAM test
    MEMORY VERIFY ERROR AT xxxxxxx
    Process
    3 beeps
    continue
    FOUND xxxx EXPECTED x.'CXx messaoe appears.
    AOH PIC #1, #2 test Continue
    A1H NMI check Continue
    A2H Interrupt process test 3 beeps
    (INT continue
    ERROR INTERRUPT AND STUCK NMI messaoe appears.
    23H A3H Protect mode test 3 beeps
    continue
    ERROR PROTECT MODE message ap'2ears.
    24H A4H Size extended RAM Continue
    2SH ASH Conventional & extended 3 beeps
    RAM test continue
    MEMORY VERIFY ERROR AT xxxxxxx
    FOUND xxxx EXPECTED xxxx messaqe appears.
    26H A6H Protect mode exception 3 beeps
    test
    continue
    ERROR PROCESSOR EXCEPTIONAL INTERRUPT messaoe appears.
    NOTE: If the error occurs on the 19H to 26H normal
    status, printer port LED status does not halt.
    Error message remains on the screen, and when the
    IRT program is finished, these error messages are
    disappeared.

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