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Toshiba T1200 internal power supply issues

compaqportableplus

compaqportableplus

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Having some issues with the internal PSU on the Toshiba T1200 I got recently.


When I first got it, I noticed all of the caps were leaking, and the entire PCB was covered in electrolyte, so I washed the PCB and replaced all caps.


Now when I plug it in, the green light comes on, but when I flip the switch, nothing happens. The motherboard board definitely works, because I was able to get it to fire up by connecting 5-volts directly to the motherboard's power connector. It booted from a floppy disk and everything.


Here's a pic of the PSU (the two big caps are bent over because the replacements were quite a bit taller than the originals, but they are fine):


thumbnail_IMG_4928.jpg


Is there a component that commonly fails on these? Or has anyone successfully replaced the internal PSU with something else? There's a lot of connections though, so that wouldn't be too easy I don't think.


And yes, the fuse is good. I've resoldered almost everything on the top side of the board to no avail.


Always loved the T1200, so I'd really like to get this thing working! Also can't wait to see if the funky JVC 26-pin hard drive works too.


Thanks!
 
Well, I tried to replace one of the chips on the board, and now the light just “blips” on the board. Put the original chip back, and the same thing still happens. Don’t know what happened. I have replaced SMD chips in the past with great success.

I think I’m just going to search for a parts unit now. I’m getting a little tired of all this eye and neck strain to get nowhere.

Surely if I get another unit I can get something that works.
 
Hi! I have the same problem with my T1200. My board is also partially corroded (I've washed it but it#s not helping).
I think I will try to use external power sources instead of the PSU to check if the laptop actually working. Main problem will be emulating signals that PSU should send to the main board (it T1200 don't have it -- I don't know).
Also it will be hard to find a device providing 22V.

compaqportableplus said:
Well, I tried to replace one of the chips on the board, and now the light just “blips” on the board. Put the original chip back, and the same thing still happens. Don’t know what happened. I have replaced SMD chips in the past with great success.

I think I’m just going to search for a parts unit now. I’m getting a little tired of all this eye and neck strain to get nowhere.

Surely if I get another unit I can get something that works.
Click to expand...
 
l4l said:
Hi! I have the same problem with my T1200. My board is also partially corroded (I've washed it but it#s not helping).
I think I will try to use external power sources instead of the PSU to check if the laptop actually working. Main problem will be emulating signals that PSU should send to the main board (it T1200 don't have it -- I don't know).
Also it will be hard to find a device providing 22V.
Click to expand...

The internal PSU in these (and all of Toshiba’s early battery-powered laptops) is utter garbage. If you come up with a solution I would love to hear it, but until then these machines are on my blacklist and I will be avoiding them.

Stick with the AC-powered units like the Toshiba T3100e. They are much better. If you want a good, early battery-powered laptop, get a Zenith. Those are very reliable in my experience.
 
compaqportableplus said:
The internal PSU in these (and all of Toshiba’s early battery-powered laptops) is utter garbage. If you come up with a solution I would love to hear it, but until then these machines are on my blacklist and I will be avoiding them.

Stick with the AC-powered units like the Toshiba T3100e. They are much better. If you want a good, early battery-powered laptop, get a Zenith. Those are very reliable in my experience.
Click to expand...

Thank you for the answer!

So far my research is here, I'm going to do a bit of reverse engineering to understand how it's working: https://docs.google.com/spreadsheets/d/1lMHF8x8NVH40P55uyTynjrBr3eQfZcRNe06QwMVCupI/edit?usp=sharing
 
About the original PSU: I have changed all capacitors and the fuse.
Result: now at least LED is green when PSU is turned off. When it's turned on (switch S1) - LED is red and blinking.

My checks of outputs with multimeter:
- PJ4: everything is 0 except two pin which are about 5V (one of the is supposed to be 5V, another is unspecified).
- PJ2: 12V instead of 5V


Good news: I have found a patent for this PSU (or very similar one) and it is expired: https://patents.google.com/patent/US5239495

I did some rev.eng. and have restored most of the PCB connections except ones under the IC14 (TMP47C440AF - that it the main controller). I have the image of the PCB itself.
And it looks like failure to provide 5V in PJ2 comes from the out 4 of IC14. TMP47C440AF is currenly rare thing to find at it is about $10 (not sure about quantity - it could be that minimal order is 100 pieces or so)
.
 
Hi guys,

Did someone find a solution for this ?
Is there some schematics available on the net ?
Can someone read the Q8 Q10 Q11 and Q19? are they all J132 ? Unreadable on my PCB.

Thanks.
 
Hi l4l,
would you be kind enough to check Q8 Q10 Q11 and Q19 if the labeling is readable ?
Are they all J132 ?
Thanks.
 
My PSU is also dead :( Can anyone confirm what is the "I0" if it is readable? According to excel sheet A3 SOT23-3. Thanks,
Branko
 
Hi romaxmaniax,
Labeling on them is unreadable (I have even used a microscope, they look like blank)
 
romaxmaniax said:
Hi guys,

Did someone find a solution for this ?
Is there some schematics available on the net ?
Can someone read the Q8 Q10 Q11 and Q19? are they all J132 ? Unreadable on my PCB.

Thanks.
Click to expand...

Hi everyone,

silence012:
1. Thank you for additional information about Q11, Q19. I've updated my Google Sheet with it.
2. "I0" is actually labeled as "A3", nothing more. I2, I4, I5 all labeled as "A9". I6 is unreadable.
3. From looking into the board itself, I suppose that further research is to manually test items. For example, to find out what item "3" is, I unsoldered it and used so-called "transistor checker" (about €10-15 from China) to find out that it is "Dual series diode" (see also Google Sheet, Tab "IC")

romaxmaniax :
1. I did additional research using another torch light and I've added even more information on the Google Sheet. Now I don't know only Q5 and Q8. Q10 is J13X (last letter is unreadable).
2. I have an unfinished multilayered PCB image of the whole board (about 90% is finished) and self-made schematics of it (about 60% is finished). If you or anyone else would like to help me, I will send it to you. PCB image needs more research with a multimeter (connectivity checks). Schematics needs more work, because many elements on the board are still unknown.
 
Does your computer show a "replace battery" prompt when the loss value is greater than 60%?
 
l4l said:
Hi everyone,

silence012:
1. Thank you for additional information about Q11, Q19. I've updated my Google Sheet with it.
2. "I0" is actually labeled as "A3", nothing more. I2, I4, I5 all labeled as "A9". I6 is unreadable.
3. From looking into the board itself, I suppose that further research is to manually test items. For example, to find out what item "3" is, I unsoldered it and used so-called "transistor checker" (about 10-15 from China) to find out that it is "Dual series diode" (see also Google Sheet, Tab "IC")

romaxmaniax :
1. I did additional research using another torch light and I've added even more information on the Google Sheet. Now I don't know only Q5 and Q8. Q10 is J13X (last letter is unreadable).
2. I have an unfinished multilayered PCB image of the whole board (about 90% is finished) and self-made schematics of it (about 60% is finished). If you or anyone else would like to help me, I will send it to you. PCB image needs more research with a multimeter (connectivity checks). Schematics needs more work, because many elements on the board are still unknown.
Click to expand...

Hi, I also have some toshiba T1200s to repair, all of them have a problem with the power supply board, 1 or 2 boards are working, I would like to recreate schematics or PCBs to reprint, how can I collaborate? Thanks
 
pedrosw said:
Hi, I also have some toshiba T1200s to repair, all of them have a problem with the power supply board, 1 or 2 boards are working, I would like to recreate schematics or PCBs to reprint, how can I collaborate? Thanks
Click to expand...
I have taken a different approach and re-created a power supply from scratch. It works, but doesn't have all of the features of the original (like battery power). But it's enough to get the machine to run.
github.com

GitHub - BasicCode/Toshiba-T1200-PSU: Replacement power supply for the Toshiba T1200 laptop computer.

Replacement power supply for the Toshiba T1200 laptop computer. - BasicCode/Toshiba-T1200-PSU
github.com github.com
 
Hi all, has anyone been able to fix their PSU to a state that isn’t perfect but works. If so would you be able to share the steps you took.
Thanks
 
I recently repaired a T1000xe to a working state. I used information I found online regarding T1600 if i recall correctly.

It was very involved. I had to replace caps and some semiconductors...both ics and psu parts.

I think these machines share architecture for the most part. There is a controller, and 4 or 5 switch mode buck converters. Someone put together a decent but approximate schematic for t1600. Useful as a road map.

For me once I more or less understood the different psu blocks, I worked through each individual pwm psu stage to see why it would not start up. A blown diode here, a bad fet there.

In the end it worked again but since I didn't want to have the hassle of battery packs, I hard wired a 12v to 7.2 v converter into the case to replace thr battery. Keep in mind that these machines seem to need the battery. Just external power does not suffice.

Anyhow it is a lot of effort but I really do like the t1000xe. I posted a repair thread on this forum.
 
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