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T1000 battery pinout

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    T1000 battery pinout

    I made the mistake of telling some work colleagues that I was interested in old computers, and one of them bought me a 1987 Toshiba T1000 that they saw in a junk shop (the one with the ROM hard drive, 512kB of RAM and 720kB floppy drive).

    It doesn't work, of course. I received it with all the screws missing from the case, and someone had half-inched the battery pack, so I suspect it may have been stripped for parts.

    Without the battery pack, it won't start up, at all. The power LED doesn't even come on. The battery's supposed to be a quartet of 1.2V nicads, producing 4.8V. I actually *have* some (pulled from my T3100SX), so I might try to bodge something up; the problem is that the battery connector has four pins, and there's no indication of what they do.

    The maintenance manual says that the voltage between pins 1&2 and pins 3&4 should be about 5V. This implies that pins 1 & 2 and pins 3 & 4 should be shorted together. Right now, with the 9V power supply connected, I'm seeing voltages ranging from about 4V to 9V across various pins, so that makes me kinda uncomfortable. Is shorting them together reasonable?

    Additionally, I'd rather like to run the thing without batteries entirely, purely off the mains; any ideas?

    Hey, look what I found. Not specs, but a decently high-res photo of somebody bodging up a new battery pack... with the red and black leads shorted together:

    (From here:


      Originally posted by hjalfi View Post
      Hey, look what I found. Not specs, but a decently high-res photo of somebody bodging up a new battery pack... with the red and black leads shorted together:

      From here:
      Take another (good)look, the two red leads are connected to the white clip (+) on the battery pack and the black leads are connected to the black clip (-) on the battery pack. No shorting at all.
      Reach me: vcfblackhole _at_ protonmail dot com.


        Sorry, that should have been phrased as 'both red leads and both black leads are shorted together'...

        Anyway, applying 5.1V (it wasn't happy with less) to the battery connector made it go beep and lights lit up and stuff. Eventually the drive pulsed. Typing 'DIR A:' and pressing return made the drive pulse again.

        But nothing came on the screen. Adjusting the contrast did nothing. It may be that it's set to the external display. I don't think I have anything which will display composite, and I haven't figured out how to change the display setting (I tried Fn plus every key on the keyboard, to no effect).

        Leaving the leads shorted together and then applying 9V to the external power socket caused the screen to flicker, the light lit briefly, then fade. Power cycling repeats this. The voltage across the battery terminals at this point is 9V. I'm going to put this as a very confused battery charger doing odd things.

        I now notice that the article I linked to stated that the battery voltage was 7.2V. I also found a forum thread saying the same thing. This is incorrect; the maintenance manual states firmly that the nominal voltage is 5V, min 4.8V, max 5.5V. Adjusting the battery voltage very slightly from 4.9V to 5.2V causes the power LED to change from red to green as it no longer thinks the battery is flat, so the hardware agrees.

        I don't think that it's worth experimenting more until I can rig up a battery, because I suspect that the power circuitry relies on having one present. Embarrassingly, though, I can't figure out how to get any of my existing nicad battery packs open --- they're all astonishingly well glued shut...


          I have pretty good luck either tapping vigorously with a rawhide mallet or just throwing them on the (concrete) floor a few times. It usually succeeds in breaking the seams open. Same technique for "wall wart" power supplies.
          Reach me: vcfblackhole _at_ protonmail dot com.


            The T1000 may be similar to the T1100 regarding the battery. See [here]. So, for a battery-less T1100, I can power it per [here].


              Brute force worked to open the battery packs.

              I wired up a battery pack and let it charge for a while. Unfortunately, something bad seems to have happened and now the T1000 won't do anything on poweron --- the power light changes colour to indicate the battery status, and it does seem to be charging the battery, but now the computer itself is completely unresponsive. Where previously I'd get a beep and about 30s later see the FDD pulse, now I get nothing. Removing the battery again and applying 5V across the battery connector doesn't work either.

              I suspect that I've either broken it somehow or an elderly cap has given up the ghost.

              The caps all look good --- no goop, no bulging. There's a mild hot-electrical smell which may be due to a white ceramic resistor which gets warm during charge. One oddity is that the power LED stays green all the time the battery is connected, even if the mains is disconnected. That doesn't seem right.

              I'm not really sure how to proceed at this point.


                I'd start by checking the larger capacitors first--it's not necessary for them to be bulging to be bad--and check that resistor's value. Its not unusual for a power resistor to change value drastically when it fails.
                Reach me: vcfblackhole _at_ protonmail dot com.


                  Please let me know how this turns out for you. I also have a T1000 with a similar issue. The power light comes on green for a second or two and turns off. Fortunately, I had the battery rebuilt using the original wires and pin header. I used (4) SubC NiCd NUN2100-CSF cells.



                    I think I'm going the shelve this one for a bit. I have a mini composite monitor (for a car reversing camera!) on order. Before doing anything irreversible, I want to check for video signal on the composite output. It's possible that my fiddling has somehow got it into a state where it's powering on successfully but not going through the usual boot sequence of a beep and a disk pulse. But it'll be a few weeks before it gets here.

                    Re the power light going on and then going off again: if it fades, then that's exactly the behaviour I saw when I shorted pins 1&2 and pins 3&4 on the battery connector, but didn't actually connect a battery. I think the battery's an integral part of the power supply and with it not present it simply won't run. So maybe your battery pack is toast.

                    If I knew more about electronics I'd be tempted to try connecting a 5V zener diode in place of the battery to see if that'll simulate the right voltage drop.


                      Update: the composite monitor arrived. I plugged it in, powered up... nothing happened.

                      So either the signal being produced by the laptop isn't what the LCD composite monitor thinks of as being a signal, or else something in the computer is fried. Either I broke it while fiddling with it, or a capacitor has faded. I'm afraid I don't think I'm up to diagnosing that. I am on the lookout for an oscilloscope with a component tester, as that'll provide a really simple way to check for dead components, but removing them from the board for testing is beyond me and I doubt I'd get a clean signal testing them on the board.

                      The one remaining unknown is that the monitor is a modern LCD job which automatically switches on when it detects a signal, and it's not. Can anyone confirm (or, preferably, deny) that a 1990-ish mono composite signal is likely to work with this? Are there any NTSC/PAL-like gotchas here?


                        Originally posted by hjalfi View Post
                        Leaving the leads shorted together and then applying 9V to the external power socket caused the screen to flicker, the light lit briefly, then fade. Power cycling repeats this. The voltage across the battery terminals at this point is 9V. I'm going to put this as a very confused battery charger doing odd things.
                        Is the original AC adapter 9V? IF you see 9V at the battery, something important was broken at or before that point, I'd reckon.
                        Twitter: @adambrisebois
                        Discord: YesterGearPC#0001
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                          Originally posted by hjalfi View Post
                          Update: the composite monitor arrived. I plugged it in, powered up... nothing happened.
                          According to the T1000 summary document at [here], a keyboard sequence is required to switch screen output to the 'External display'. 'External' may include both RGB and composite ports.


                            So I found an oscilloscope and had another go.

                            The PSU sort-of works, and is feeding sort-of 5V onto the board. I'm increasingly unhappy about it PSU, because the board voltage appears to be exactly what's coming out of the batteries, which can vary from 3V to 5.1V depending how tired they're feeling. So I've given up on the batteries and the 9V external power supply and am instead just feeding 5V directly into the battery terminals.

                            So now that it's got clean power, I can find 5V power lines at various points on the board, which means that power propagation is working. The composite port and the RGB port remain completely dead. There is some activity on the LCD connector. I found a 500khZ signal on one pin and a 2MHz signal on another pin, but the screen doesn't show anything. I tried to look for a clock on the processor but it's an exotic M80C88A QFP package and I couldn't find the pinout...

                            The first time I powered it up, it beeped. Then about 30 seconds later it beeped again, and the drive chugged, which indicates it was working through the bootup sequence. But it was disassembled on my bench and the screen was disconnected, so I didn't see anything, and it didn't do it again.

                            This feels like a marginally borked component. I can see power everywhere, so that suggests it's not the PSU, but the maintenance manual states that the LCD takes +5V and -22V, and I certainly didn't see -22V on any of the LCD connector pins. If the PSU has failed in some way where it's mostly failing to generate the right voltages, and the reset logic is waiting for all the exotic voltages to stabilise, that would explain the symptoms I'm getting...

                            Oh, and just to make life more fun, the manual on minuszerodegrees is for a different issue of the board than I actually have, so some of the jumpers are different.

                            There aren't very many PSU capacitors, and none of them are bulgy. I suppose I could just remove them all and test them, but given my soldering skills that risks irreparably damaging the board.



                              More than just capacitors can die in power circuitry, I've had all sorts of grief with dead transistors, mosfets and diodes. Another annoyance is if an optocoupler goes away or starts misbehaving, it can cause the output power rails to go crazy or just fail to work.