Toshiba T1200 internal power supply issues

[Pucehaddock6576]

Was just wondering how would I power the -22 and -9 volt rails on the power supply ? Would I just be able to use a normal dc power supply and just connect the ground to the -22 rail and 22v from the bench power supply to the ground rail of the computer. I just can’t wrap my head around how I would power it externally. If someone could please explain how I should wire it to test if the main parts at least work.

 

[Twospruces]

What model computer?

Can you post hi res photos of the psu?

I think if you know which rails are which, and the voltages, then you should be able to isolate the psu and supply with all external rails.

Power supply sync might be a concern on power up?

 

[Pucehaddock6576]

The psu is from a Toshiba T1200. A few years ago I found it in the trash, brought it home and decided to try power it up without doing any research, then it showed the red blinking light, only later I decide to open it and discovered that the capacitors were leaking. As i was inexperienced I didn’t know how badly I messed it up so i decided to start disassembling it and creating a wiring diagram to help troubleshoot the board which got me to some places as I could switch some of the visually broken parts. It’s been about a year since I last worked on it and have decided to work on it and ask as many questions while the few people who have a working one of these or knowledge that might help me. I thought I should at least check if the rest of the computer is ok and attempt to power it up with some desktop power supplies, I’m just not entirely sure how I should wire it so I don't create any magic smoke. How would I create -22 volts and +5 volts while using a dc desktop power supply ? Where should I connect the ground for the -22 and +5 ?

 

[Twospruces]

I think what you want to focus on is the motherboard. How does this psu connect to it. What pins are what rails.

That psu looks pretty disassembled!

 

[BikeForever]

I got a board from tommy_tom2000's design. But I used switchmode dc/dc for all voltages. By using ones with an isolated 24v and 9v output. Connect the +ve output to ground, then the -ve output is at the required voltage below ground. It takes careful wiring but is working fine.
I have spare boards as JILPCB has a min order of 5, so anybody UK based wants one, just pay postage.

 

[wandariam]

I'm new here. Just looking around. I bought a t1200 from a recycling center
50 bucks. It would turn on do a memory test and tell me to insert a boot disk. About a year later after being in the vintage world I understood more and did my research to find a boot disk through some archives. Made a 3.5 boot disk from my persario and it booted up. Dos 3.3. The screen is just ok. A ribbon appears but I can still read it. I took college classes back in the 90's and they offered dos 5.0. ok back to the spec. Upset at the fact that the recycling center removed the working hard drive. Privacy issue I assume. Left me with 1) 3.5 drive. I have forgotten most of my dos knowledge. I was able to hook up a external monitor for a bigger viewing experience. The battery pack doesn't hold a charge but I remember seeing another battery sitting on top. A longer battery. Not sure what this does. Anyways this post is getting too long.

 

[BikeForever]

I'm new here. Just looking around. I bought a t1200 from a recycling center
50 bucks. It would turn on do a memory test and tell me to insert a boot disk. About a year later after being in the vintage world I understood more and did my research to find a boot disk through some archives. Made a 3.5 boot disk from my persario and it booted up. Dos 3.3. The screen is just ok. A ribbon appears but I can still read it. I took college classes back in the 90's and they offered dos 5.0. ok back to the spec. Upset at the fact that the recycling center removed the working hard drive. Privacy issue I assume. Left me with 1) 3.5 drive. I have forgotten most of my dos knowledge. I was able to hook up a external monitor for a bigger viewing experience. The battery pack doesn't hold a charge but I remember seeing another battery sitting on top. A longer battery. Not sure what this does. Anyways this post is getting too long.

There are 3 batteries in the T1200. The main one accessible from the outside at 7.2v is a nicad pack. There is a smaller pack just inside the case, at the back above the rear ports, that is the backup battery for the ram disk, also nicad. And then buried under the keyboard is the bios battery which can be replaced with a CR2032.

 

[solidpro]

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 - 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

tommy_tom2000 - do you know if that recreated PSU design would go into a T1100 or T1100 plus? Thanks!​

 

[Istarian]

Given that this is a laptop, which I presume originally shipped with a battery, perhaps the PSU doesn't function properly without the load presented by a battery?

And if the system requires both the PSU and the battery to startup, the PSU alone may not be able to provide enough juice to run the machine directly off of AC power.

I would view that as a flawed design, at least with 2026 hindsight, but it might have been deemed acceptable at the time.

 

[solidpro]

You're right, the T1100, at least will not function without a connected main battery. However I know that my power supply also has a fault.
I suspect the recreated board perhaps doesn't have the requirement of the battery.... it's a shape it's a project that started and finished with seemingly no evolution - does it work in other models? It looks like it has the same connectors as required for the T1100plus, so I don't see why not...