Toshiba T1000LE – These things just don’t want to work

As anyone familiar with these older battery-powered Toshiba laptops knows, these things are finicky at best when it comes to their power supplies. Especially electrolytic capacitors and, apparently, MOSFETS are a problem.

The good

A year-and-a-half ago I posted about my T1000LE and that it was back to life.
That, as it turns out, was a temporary situation.
After replacing all the caps and the burnt-out MOSTFET labeled on the PCB as Q502 the machine actually worked quite well for a while.
I even went as far as to re-cell the battery and source a second machine in a worse physical condition so I could use it’s harddrive and used the machine a couple of times over a period of about 4-5 months.

As I now had 2 of these I wanted to get the second machine working as well so I ordered capacitors and got to work on the second machine.
This one powered right up after replacing all electrolytics, great!

Well, not so much as it turns out.

The bad

After a while the first machine started acting up. It would not boot in fast mode. “Fast” being relative here as it is only 9.54MHz.
As soon as the BIOS POST was done and the machine started booting it would crash, blinking the red DC IN LED but would work perfectly fine in slow mode (4.77MHz).

Luckily, I still had the second machine to play with, no worries.

The ugly

Last weekend, while working on a related project (which I will write about on a later date) I needed the T1000LE to test some things. Connected the powerbrick, turned it on and…. nothing.

So, I grabbed the first machine. Even if it only runs in slow mode, it runs, right?

Nope. Nothing.

Both machines now show the exact same symptoms the first one did before I found out Q502 was burnt out. Opening up the second machine I immediatly spotted a burnt Q502. Darn it.

The really ugly

After some quick troubleshooting it seems that Q502 is an integral part of the powersupply. The machine simply doesn’t work without it. No flashing LEDs, nothing.

So now I will have to find out what causes this and especially why it only happened after some use.
It could very well be some inferior quality electrolytic capacitors that I used so I’ll be replacing some of them with a good brand like Panasonic.
Besides that, I will have to order some new 2SJ182 MOSFETS again.

After all of that is done there will be a lot of probing around with an oscilloscope to try and find out what is causing this issue. The entire power circuitry for these machines is a mystery to me. It uses a lot of SMD components and is spread across the power board, LED board and main board.
The PCBs all being multi-layered with some blind via’s doesn’t really help either.

On top of that, no schematics exist for these machines and the maintenance manual doesn’t contain any voltage references. Even the pinout tables are quite cryptic and hard to make sense of.

The only (somwhat) positive thing about this is that at least I have something to do during the lockdown situation due to COVID-19.
That also gives me the oppertunity to update this blog more often, so check back here in a few days for an update.