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Toshiba T1900C

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
263
Location
Finland
Went today to old school building in Varkaus, Finland.
Building is going to be demolished next week and they were giving
away all furnitures and basically anything, that people could just carry away.

I did pick up some tables and chairs that I can use, but to my surprise,
there were also some computer hardware. Got couple of fujitsu siemens desktops
with flat screen monitors and keyboards, mice and cables included.

But most interesting found was this Toshiba T1900C.
It did not come with needed 18V power supply however. I need to figure out
where I can get suitable psu for it. Most likely the battery has died long time ago,
but I guess it could work with just the psu. Interested to find out if it will still work.
 

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VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
263
Location
Finland
toshiba.jpg

I found 19V power supply (Toshiba requires 18V). With it, I do get green led (DC IN) on.
Battery led is blinking orange. Very obviously the battery must be a goner.

I try to boot the laptop with this psu connected, but battery led goes away and DC IN green
led stays green, but starts to blink 1 long and 3 short blinks. And keeps repeating this while the
screen remains empty.

I realize, that the toshiba migth just refuse 19V psu, but it could be something else too.
I could not find blink codes from the internet. There was the manual for t1900c, 183 pages;
I did skim through it, but could not really find help from it either.

Anyone got idea of the DC IN -blinking codes ?

Seems, that failing caps are also a common problem with these, but in those case descriptions
toshiba tryes to boot and something is shown on the screen. This one got black screen all the time.

Laptop also remains completely silent. I guess, it is not allowing power to go to the hard drive.
Maybe this could hint to mismatching psu. It just might be too picky on that.
 

DeltaDon

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Joined
Oct 26, 2016
Messages
514
Location
Dutchess County, New York, USA
Most laptops are not critical of input voltage as long as within a volt or two. The voltage has to be higher than the full charge voltage of the battery to be able to charge it. Otherwise, the voltage is regulated in the first few circuits found in the charger input. A few early laptops would not boot if there wasn't a battery installed, might have used the battery as a large capacitor?? Don't know if the Toshiba was one.

I also don't know anything about that blink code, but there were only a few BIOS writers back in the early days, Award and Phoenix comes to mind and searching for their blink codes might reveal the correct data.

The CMOS battery might be dead or needing a charge (if rechargable) and try leaving the adapter pulled into it for a few hours to see if it charges the CMOS battery. Also, a trick I've used on main batteries that won't start charging is to remove it and plug it back in a few times while the adapter is also pulled in. Each time you put a pulse of power to the battery and therefore give it a small charge. If you can get the battery's circuitry to power up it might allow the charge to begin normally. If the cells are shot they might only supply a few minutes of run time, but you can at least see if the battery is rebuildable.
 

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
263
Location
Finland
Thanks all for your input!

I have not yet opened and checked, if there are leaked caps inside.
Very likely there are, if the laptops are not picky of exact voltage.
I will check with multimeter, what does the psu actually gives. But it seems, that I need to open
it up and check the capacitors.

I have tried to boot with the battery installed and without. But of course, the battery itself must be defective for its long age.
I did have the psu connected over night, but that did not change the situation.

I have not tried that trick to remove battery and reinsert it, while psu is connected. I will try that just in case.
 

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
263
Location
Finland
So, I decided to take the laptop apart.

1.jpg
2.jpg
3.jpg
4.jpg
5.jpg
6.jpg

On the way to possible cause (electrolytic caps), I checked internal batteries.
Amazingly that small coin lithium battery was showing 3,00 V. On the other hand,
it might have been replaced some time during the laptops life. The green finger battery
was completely dead.

I removed the batteries and had a try - no chance to the symptoms. Still one long green led flash and three short ones.

All caps look externaly fine. 1000uF cap has been a known issue, so I tried to pull it from pcb. No change to behaviour.
There was neither any chance after pulling the bigger brown 2200 uF cap.

I checked, that pcb gets +19,26V near the power connector. The big dark blue cap near the power connector gets above 18V too.
Two light blue caps (near the removed smaller brown cap) get about 2V each (one slightly under 2V the other slightly over 2V).

Voltage on the removed brown caps is a bit inconclusive. At times they get zero, but I have also read just above 1V from those
connectors. Trying a push to power on -button gets these connectors have a short burst of low <1V voltage, but voltage drops
almost immediately to zero after releasing the power button.

I'm not sure what could I try next. I was under impression, that shorted electrolytic caps might be the issue, especially that
1000uF cap, that has been known issue. But not really sure now, though 2V on the ligth blue caps could still suggest
a short somewhere. But none of the caps show short if I try with ohm values, they show at least >300 ohms each. At least
I'm assuming its not a short, since there is some level of resistance (enough or not... ) .

Two small brown caps (right from two light blue) are showing no voltage. But I guess it might just be due to computer not starting
up.

Oh well... back to the drawing board.
 

DankEngihn

Member
Joined
Nov 28, 2019
Messages
46
Location
Ontario, Canada
What about the capacitors on the motherboard?

Are they ok too?

Did you check the ESR of the capacitors? That'll drift out of spec if the capacitors start failing.
 
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VintageVic

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Dec 9, 2019
Messages
263
Location
Finland
7.jpg

I cant see any electrolytic caps on the motherboard.
I'm quite novice with electronics, is it possible to measure ESR with just multimeter ?
 

DankEngihn

Member
Joined
Nov 28, 2019
Messages
46
Location
Ontario, Canada
Depends on the multimeter you have.

They're not electrolytic capacitors, they're SMD tantalum capacitors, which when they fail, fail short.

Have you tried powering up the board with nothing else connected? Just the two boards and a charger?
 

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
263
Location
Finland
Depends on the multimeter you have.

They're not electrolytic capacitors, they're SMD tantalum capacitors, which when they fail, fail short.

ah, I see. Thank you for explaining this out.

Have you tried powering up the board with nothing else connected? Just the two boards and a charger?

Yes, all the boot attemps I described here today I did with the two boards only + charger.
Well, I did have the screen connected as well. I will make one more attempt unplugging the screen
and see if there is any change in the DC IN led behaviour.
 

Stone

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12,814
Location
South Jersey, USA
I cant see any electrolytic caps on the motherboard.
I'm quite novice with electronics, is it possible to measure ESR with just multimeter ?
In general, testing capacitors is not a simple task. A multimeter is not normally sufficient on its own. An ESR or capacitance test would be much more definitive. Overall it's way more involved than it might seem on the surface. In some cases, removing the capacitor(s) from the circuit is the only tried and true method and that alone can introduce further issues.
 

DankEngihn

Member
Joined
Nov 28, 2019
Messages
46
Location
Ontario, Canada
It's possible for capacitors on the inverter board of the screen to fail.

If still nothing, try hooking up a speaker to the parallel port. Some laptops emit beep codes from the parallel port

EDIT: what power supply are you using? Post a picture of it. The DC led can blink like that if it detects abnormal voltage.
 

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
263
Location
Finland
It's possible for capacitors on the inverter board of the screen to fail.

If still nothing, try hooking up a speaker to the parallel port. Some laptops emit beep codes from the parallel port

EDIT: what power supply are you using? Post a picture of it. The DC led can blink like that if it detects abnormal voltage.

I unplugged the screen and no change in the DC IN led behaviour (one long + three short blinks repeating).
p-port.jpg

from t1900c maintenance manual it is revealed, that I could try to construct LED checker for error code. That is then
plugged to the printer port. I would need to find out how the pins are connected to the leds, then I might construct one.

And yes, it is still possible, that all this effort is just due to mismatching psu. That is the one I'm using and it is not original to this laptop.
Toshiba power connector has marking 18V.
psu.jpg
 

DankEngihn

Member
Joined
Nov 28, 2019
Messages
46
Location
Ontario, Canada
Try hooking 12 volts up to the battery terminals directly, without the charger.

It's most likely a bad capacitor on the power board.

EDIT: Make sure you get the polarity right, or it'll cause more issues.
 
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VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
263
Location
Finland
In general, testing capacitors is not a simple task. A multimeter is not normally sufficient on its own. An ESR or capacitance test would be much more definitive. Overall it's way more involved than it might seem on the surface. In some cases, removing the capacitor(s) from the circuit is the only tried and true method and that alone can introduce further issues.

Yeah, I was a bit suspecting, that my simple multimeter is not up to the task to measure ESR.
I might not be either, heh heh.

I could just pull out more caps from the board and see if anything changes. But perhaps a short break
to think what is the best course of action is in order. I do not have new spares at the moment and it probably
will not work either when all caps are pulled out... I might use scrapped atx power supply, if it has matching capacitors
for a replacement. New caps are cheap to order from china/ebay, but recently it has taken 6-10 weeks before orders have
arrived here. I'm not in a hurry, but that is a bit ridiculous :).
 

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
263
Location
Finland
Try hooking 12 volts up to the battery terminals directly, without the charger.

It's most likely a bad capacitor on the power board.

EDIT: Make sure you get the polarity right, or it'll cause more issues.

That might not be a bad idea to try!
wow... but let me take a moment to figure out how to connect 12V to five contacts :).
There is 0,45 Volts across leads marked with + and - . I mean, those two leads that are
most far from each others. I guess it might be right place to connect +12 and ground.


batt.jpg
 

DankEngihn

Member
Joined
Nov 28, 2019
Messages
46
Location
Ontario, Canada
Only connect it to the two on the edge!

In your picture, the far right is negative, and left is positive!

The middle 3 are ground!

DO NOT CONNECT THE THREE MIDDLE CONTACTS TO POWER. YOU WON'T HAVE A GOOD TIME.

Connect it to the terminals on the motherboard. Not the battery.
 

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
263
Location
Finland
Only connect it to the two on the edge!

In your picture, the far right is negative, and left is positive!

The middle 3 are ground!

DO NOT CONNECT THE THREE MIDDLE CONTACTS TO POWER. YOU WON'T HAVE A GOOD TIME.

Connect it to the terminals on the motherboard. Not the battery.

Right! No worries, I gave it a go, connected +12 to the far left (on motherboard) and ground to far right.
-> still the same behaviour with the LEDs.

It was a good try anyway, my shaky gut feeling tells me, that if the motherboard was ok, that 19V psu would
fit it just fine. And I can always try to use ATX psu 12V on the two terminals later also, just to make sure.

8.jpg 9.jpg

I made final attempts to pull the two light blue caps one by one and tested after each pull.
Still no change. I pulled these two, since someone had experienced that these were also bad.

But, I think I am going to sleep over this now. It's late here and early wake up for work in the morning.
Thanks again for all suggestions!
 
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