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Toshiba T1200 schematic

Twospruces

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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
 

rimmeruk

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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.
 

compaqportableplus

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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.
 

Twospruces

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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.
 

compaqportableplus

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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.

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).
 

rimmeruk

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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.

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.
 
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rimmeruk

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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.
 

compaqportableplus

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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.
 

rimmeruk

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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 ?
 
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rimmeruk

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Toshiba T1200 LED Error Codes

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 xxxx:xxxx
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
(INT8) 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 xxxx:xxxx
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.
 

compaqportableplus

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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 ?


That's interesting about the post codes. Didn't know the Toshibas had that. I knew machines like the IBM PS/2 did though. And yes, I replaced ALL of the capacitors with brand-new, name-brand components. None were missed.


I did not use an LPT code reader, but I DO have one, so lets not assume things here. I am very serious about repairing vintage computers and have restored many.


I actually wasn't lucky at all with the Compaqs. The Compaq SLT is a very well-engineered machine. You don't just get lucky six separate times on one type of vintage computer. If you get six units all from different places and they all work, it's a damn good machine. Period.


Let me be very clear about one other thing too: the Toshibas were not my first rodeo. They are far from it, in fact. I am not a newbie. I don't consider myself an "expert" by any means and never will, but I do know a little bit about vintage computers.


Some of the systems I have repaired include the two Compaq LTEs that had capacitor damage, which required me to hunt and repair broken traces with a magnifier and a multimeter. They are fully-working now, and have been for over a year (see this thread about them: http://www.vcfed.org/forum/showthread.php?69252-Compaq-LTE-8086-repairs). Or the Compaq Portable I spent about a week diagnosing the dead CRT on, which, after swapping some parts around and looking over the schematic for a while, I determined was the horizontal output transistor, which I replaced, and the CRT worked fine afterwards.


That being said, I'm not saying there is no way the Toshibas I have couldn't be fixed by anyone, I'm saying the issue was NOT just the caps, as they have ALL been replaced and the machine still doesn't work. I also cleaned the PSU board VERY well.


Pretty sure I mentioned this above in another post, but I will say it again: I have seen several other cases of people replacing the caps in these early (pre-386 era) Toshiba laptops and it not fixing the issue. I'm not the only one.


And I'm sticking to it about the design of these being flakey. I have worked on/repaired/recapped lots of vintage PCs/Macs and I have never seen anything as temperamental as these early Toshibas (just the early ones, 386 and later units seem to be very reliable). Hell, I successfully restored a Macintosh Portable even (one of the most temperamental Macs ever). But these Toshibas are something else, that's for sure.


And another thing, I have nothing against Toshiba, I've got a T3100e, 2 T5200s (gray AC-powered plasma models, very reliable) and some newer 486 and Pentium models (like a Libretto 50CT among others), and they are all great. Some of the better machines I have actually. But their early battery-powered machines just aren't reliable enough to warrant me owning them.


About the Zenith, I'm pretty sure you mentioned Zenith's odd power supplies above. That's what I'm talking about.
 

modem7

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I actually wasn't lucky at all with the Compaqs. The Compaq SLT is a very well-engineered machine.You don't just get lucky six separate times on one type of vintage computer. If you get six units all from different places and they all work, it's a damn good machine. Period.
But maybe all six were repaired under warranty and/or repaired subsequently.
 

compaqportableplus

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But maybe all six were repaired under warranty and/or repaired subsequently.

Some of them have had the hard drives replaced and memory upgraded, but beyond that, they don’t appear to have had much else done to them. These machines don’t break much even at 30-plus-years of age, so I’d say it’s unlikely all 6 of mine had major failures back in the day. That’s not to say an SLT never broke, obviously anything can happen, but they aren’t trouble prone by any means.
 

compaqportableplus

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Some of them have had the hard drives replaced and memory upgraded, but beyond that, they don’t appear to have had much else done to them. These machines don’t break much even at 30-plus-years of age, so I’d say it’s unlikely all 6 of mine had major failures back in the day. That’s not to say an SLT never broke, obviously anything can happen, but they aren’t trouble prone by any means.

Also, all six were from different purchases. I didn't buy them in a lot from the same place or anything. Sorry if I didn't make that clear.
 

rimmeruk

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You'd be surprised how missing a single SMD tantalum capacitor can prevent the machine from powering up or functioning correctly.
The Toshiba T1200 has many small SMD tantalum caps that leak but also don't show any external signs of failure. It's not just the
obvious electrolytic caps that should be replaced.

As for the vintage 386/486 Compaq's, I agree they are great machines, but just as likely to have the same issues. I've repaired many
Compaq, Toshiba's, Dell, IBM etc.. and some are more favourable to work on than others. Compaq are very easy to dissasembe and access
the mainboard, so too some Toshiba's, esp the T1000/T1200 series. Compaq made their machines more accessable more than any other
manufacturer laptop I've worked on. Compaq do seem to have a alot of screen failures or issues with the display.
The T3000/T5000 series are a figgin nightmare of a machine, I've had 2 units arrive to me and I quickly sold them on, it was like dissmantling a tank.

Yes, I've read some of your posts and your photos with descriptions have helped me with some of my repairs and I thank you for that.
Sometimes, these old vintage micros can be hiding a very simple repair, that even the most knowlegable electronics guy could overlook.
I spent days on one particular machine, that would just refuse to boot or power up. Turned out to be a corrupt CMOS memory
chip. There was even 2 jumper pads on the board with it silk screened to reset the CMOS chip. I had to place a solder blob over the
pads and power on. I was just kicking myself when it finally booted with just a CMOS error. Sometimes removing the batteres does not always
reset a CMOS chip and many chips have external pads for jumpering to do this.

Just something to take into account when working on these machines, it is not always the caps that prevent them from powering up.
The BIOS/CMOS is the first call from the CPU and if that comunication fails then some machines will fail to boot. Still, all the caps
should be replace as a matter of course, as they too are integral to the correct operation of all the components and power supply.
 
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rimmeruk

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Toshiba T1200 Power Board

Toshiba T1200 Power Board

Here is a photo of the main power board for the Toshiba T1200.
All of those elctrolytic caps must be replaced and I have also highlighted 2 SMD tantulum caps which
also must be replaced. The large one is 10uF 16V and the smaller one is 3.3uF 16V. You can use standard
electrolytic caps to replace the SMD tantalum's, if your OCD will allow that :) Just shorten and bend the legs
into an L-shape and solder to the pads.

I don't use hot-air guns to remove SMD caps, usually when they leak they are very easy to gently twist and pull
away if you heat one side with an iron. The round SMD caps are very easy to remove without any heat by gripping
them with some long-nose pliars and gently twisting them off in a circular motion. I very rarely rip the pads
using this process if I'm careful enough. In fact, using hot-air on SMD caps will cause the pads to lift.
The board can then be cleaned with IA and the pads re-tinned with some solder.
 

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compaqportableplus

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rimmeruk,

There was one cracked tantalum cap on the 1200’s PSU board I replaced and I did check the other and it seemed fine, but maybe it isn’t.


And yes, I agree that things can get overlooked quite easily. I’ve done it many times and still do occasionally.


Also, something I want to reiterate; I was in no way claiming above that a Compaq has never broken and that they are 100% immune to problems, that would be silly, but I can genuinely say that I have never had a major issue with any SLT and I have had one of them for almost 10 years now. Again, not to say one could never malfunction, but they are definitely more reliable than some of the others.


And another thing I want to reiterate, I’m in no way saying I am the “best” at repairing vintage computers, and I hate arrogant people that feel that way. There are many people on this forum and elsewhere that are far more experienced than I. I’m always eager to hear advice from other people that repair this stuff. The only point I was making above is that I have fixed a few of these things before.


I am very happy to hear some of my posts have helped you.


Thanks for that photo. I did have a chip unsoldered from the PSU board in that machine though, so I’d have to dig those parts back up and reinstall that chip to do any testing.
 

rimmeruk

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You're welcome, I don't believe anyone or claims to be an expert :)

There are even more SMD caps on the main logic board to replace, it's a pain in the ass job when you start, but the reward is worth it guess.
 

CedsRepairs

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I'm in the same nightmare on a T1100 repair. I see than T1200 sound difficult to fix as well.

The "power supply" (I'd rather call it a DC-DC converter) that I tested (see my post) actually seems fine, le'ts say acceptable, even with stock capacitors which are extremely high quality + all tested ok.

I believe, as CompaqPortable does, that something ELSE than the powersupply dies in those with time passing by.

I've located a malfunction in the TTL logic ( 74HC245 HC373 ) close to the CPU.
Still a bit early to say exactly what the problem is, but i'm closing in. It's also likely that is is old/failing powersupplies that kill part of the logic.
 

rimmeruk

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Can't find your post. I've attempted a repair on a T1100 but in the end I just had to source a new mainboard, too much corrosion and track damage.
The faults are caused by caps electrolite or battery acid eating away tracks or shorting the components.
The IC's in Toshiba's and Compaq's are of a very high quality and reliabilty, they very very rarely just fail. Unfortunately it's the
capacitors and batteries that have a short shelf life and ultimately destroy every other component and track connected to them.
This is mainly the result of someone powering them up after they have been left unpowered for years and without inspecting the board first
or using a current limiting power supply :)
 
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