Toshiba T1000XE repair thread

[Twospruces]

I recently bought a T1000XE with problems. Thought I would start a thread specific to this machine, and capture what I find.

some related threads:

Toshiba T1000XE - Old Crap Vintage Computing

Toshiba T1000XE has a similar specification to the IBM PC Convertible, with a 4.77MHz 80C88 CPU, 512KB RAM, and a monochrome CGA.

oldcrap.org

https://forum.vcfed.org/index.php?threads/what-are-typical-issues-for-toshiba-t1000les.53994/page-3#post-929397

Debugging the T1000LE PSU - Thom Wijtenburg

Now I own a third, working T1000LE it is time to do some testing, tracing and debugging on the other machines to once and for all fix the PSU

thomwijtenburg.nl

https://forum.vcfed.org/index.php?threads/toshiba-t1000le.66905/#post-822219

https://forum.vcfed.org/index.php?threads/toshiba-t1000xe.1917/

This machine will not power up. The NiCd 7.2V pack is totally dead. The internal SUB BATT, which appears to be 5 AAA 1.2V NiCd, is also dead.
There is a 3rd battery, which is a small 2 cell 2.4V NiCd. Unclear if it is also a goner.

There are 2 PCBs that need attention. The main board of course, and additionally the LCD PCB that mounts in the top cover.

The PSU is the initial culprit. Found several caps that were leaking, but very little damage to PCB that I can see.
The capacitors that were leaking were:
470/25V
47/16V
56/35V
120/16V

Here is a list of capacitors, and suggested replacements:

dimension inches
Main PCB
leaded electrolytic
qty designation value diam height lead spacing digikey part number brand
2 no markings 470/25V 0.4 0.85 0.2 B41888C5477M000 Epcos - TDK
1 C576 220/25V 0.4 0.55 0.2 860130475006 Wurth
2 C507 220/10V 0.25 0.5 0.1 860040273002 Wurth
1 C510 1200/16V 0.5 0.8 0.2 860010375018 Wurth
2 C512 C511 1800/10V 0.5 0.8 0.2 EEU-FS1A182B Panasonic
3 (4) C513 C514 C516 56/35V 0.25 0.5 0.1 860040573003 Wurth
1 C180 47/16V 0.25 0.2 0.1 ECE-A1CKS470 Panasonic

LCD PCB
qty designation value diam height lead spacing digikey part number brand
1 (0) C804 56/35V 0.25 0.5 0.1 860040573003 Wurth
1 C803 120/16V 0.25 0.5 0.1 860160373012 Wurth
2 C802 C801 10/25V 0.2 0.2 0.1 ECE-A1EKS100I Panasonic


The HDD in my case is a JVC JDE2825P.
I was able to mount this in an old PC, format it and install MSDOS 3.3.
This drive is compatible with the Connor CP2024 and also CP2124, so I think that means it is an IDE drive.
Nothing proprietary that I can see.


So, hoping that I will only need to recap this board to get it working.

I have read that this machine may or may not require a working battery to boot up; once I get the new caps in place, I will see what progress I can make.

To replace the NiCd main battery pack, I have kluged into place 6xAA NiMh cells. I have also kluged 5xAA NiMh cells in place of the SUB BATT. I'll probably replace the 2x nicd cells with a similar 2xnimh cell.

Once I get it booting I will selectively eliminate batteries to see the effect.

I really don't know the function of the SUB BATT.

Anyhow, I'll see what I can do with this machine.

 

[Twospruces]

I replaced all the electrolytics and... no change.

So,... going to have to start checking out the various semiconductors to try and find something broken. I did notice a diode of some kind that was overheated.

There is a guide online that was shared ( will post a link) with methodology for fixing these toshibas. I suppose I should follow the program...

 

[Twospruces]

OK, after a fairly intense amount of effort, I have a T1000XE that so far seems to work.
I`ve attached some notes and information to this post.

It wasn`t just caps; some parts were blown too. With no schematic, tough to debug.
However, the T1600PSU schematic done by Fust is a really good start. While not exactly the same... you get the drift on how it works.

GitHub - fust/T1600-PSU: Schematic and troubleshooting guide for the Toshiba T1600 Power Supply board (PSU)

Schematic and troubleshooting guide for the Toshiba T1600 Power Supply board (PSU) - GitHub - fust/T1600-PSU: Schematic and troubleshooting guide for the Toshiba T1600 Power Supply board (PSU)

github.com

Anyhow, my list of caps is here, and the things that broke are described a bit.
I also annotated a photo of the PSU primary side with the part of the PSU each component relates to.

Hopefully this will help others.

I did confirm that the T1000XE does not like to try to operate without a good main battery.
It seems to ignore a missing sub-battery so that`s good. No need to replace it.

Also, note some changes to my original post:
1) the sub battery is not AAA based. the batteries are smaller.
2) my CMOS battery was actually ok, just not charged.

 

[Twospruces]

One observation, and I don't know if it is an issue.

I have made a replacement battery using 6x AA nimh cells. Not Nicad.
I believe that the computer will not run without a good battery installed. At least I think that is normal.

What I observe is thata even with the external power adapter plugged in and providing power, the battery continues to drain. So eventually you run down the battery and the machine shuts down.

This seems really strange. One would think the computer should be able to run continuously with external power.

So this makes me think I have a problem in the charger circuit.

Anyone else have a working T1000xe and able to confirm how the external power works?

 

[Twospruces]

A solution that is pretty easy for the sub battery is to disassemble a 9V nimh battery. Inside there are 6x AAAA cells. Pretty easy to make a 5 cell sub batt from that.

 

[silence012]

I have a working T1000XE but I don't have a main battery in it. I use it by connecting bench power supply directly on battery leads.

Will see if I can find 6 nimh battery around and try it.

 

[Twospruces]

If I understand correctly you just use a bench supply at something like 7.2VDC to power the XE at the battery contacts.

You can't use the external power brick by itself? I ask because on my machine the external power brick, with no battery installed in thr laptop, cannot power the machine.

There is one P channel e MOSFET that controls how much current is sent into the power circuit from the external power brick. I'm going to trace out the circuit that controls the gate voltage of that FET, and see if I can understand why I can't source enough current to operate the laptop steady state from the external 12V supply. Maybe, because I am using NIMH and not NICD Batts, this small change in VI curve has altered the bias control on this big FET. Or maybe I can tweak the circuit to increase the current flow.

I did check out the transistors on a tester and they seem ok, so I don't think I am dealing with blown components.

 

[silence012]

If I understand correctly you just use a bench supply at something like 7.2VDC to power the XE at the battery contacts.

That's correct. I put ~8.2V there and it work great! BTW, most of the laptops that you can find now days do not have the PSU anyway

You can't use the external power brick by itself? I ask because on my machine the external power brick, with no battery installed in thr laptop, cannot power the machine.

No, you can't. The same goes to T1000SE. I think the T1000LE is the only one that can be powered without the main battery but I might be wrong as I haven't power it up for a while

There is one P channel e MOSFET that controls how much current is sent into the power circuit from the external power brick. I'm going to trace out the circuit that controls the gate voltage of that FET, and see if I can understand why I can't source enough current to operate the laptop steady state from the external 12V supply. Maybe, because I am using NIMH and not NICD Batts, this small change in VI curve has altered the bias control on this big FET. Or maybe I can tweak the circuit to increase the current flow.

I don't think it is anyhow related to NiCd or NiMh battery. It is just designed like that. If there are limitations like you said, I would not try to modify it. Better just buy a cheap bench power supply and use it instead.

I did check out the transistors on a tester and they seem ok, so I don't think I am dealing with blown components.

 

[Twospruces]

I`ve pretty much concluded my efforts to get this T1000XE working again.
I`ve made a compromise that I`m quite happy with.

I was able to repair the power supply to the point where it would run off battery power until the batteries died.
However, the PSU was unable to provide enough power from the external supply to maintain charge in the battery.
So, even with the external power included, it would eventually run out of battery.

I could have spent more time trying to figure out why that part of the PSU did not work, but I was worried about damaging the board. In other words, it was about as good as it was going to get.

So, instead I decided to swap the batteries for a switching power converter.

I feed power to this little converter from the external supply, and feed the output 7.2V to the battery terminals.
The converter mounted fairly easily inside the case.

So, now the machine has a ``simulated infinite battery`` fed from the original external power adapter.
It is working great now. I`ve removed the old nicads from the battery pack, but otherwise it looks stock.

The only thing I notice is that the green `battery`LED does not come on any more. To fix would involve yet more debugging without a schematic, so...I`ll live with that problem.

It is really a nice laptop to use. Screen is excellent, keyboard is great. External floppy needed repairs too but that`s working great as well.
Norton Commander software to transfer files to/from a windows98 box on my network to get access to software etc.