On the vias in the white silkscreen surrounding the capacitors, it looks like there's still some electrolyte / residue there. Washing it in an ultrasonic would probably help, but in my case I cleaned it up extensively while the capacitors were off the board.
My T1950CT had the same issue as you're seeing now originally where it would only power on after being heated for a while, but replacing the C511 cap & cleaning resolved the issue on mine.

I re-removed some capacitors (including the C511) and cleaned the board again with IPA and toothbrush, and tried with another C511 replacement (Sanyo), same result 😒

Another card, same symptoms, I removed most of the capacitors, I completely immersed the card in IPA for about 30 minutes then I scrubbed with a toothbrush and dried with a hair dryer, no change, the card only works when it has been heated. I tried with different values of replacement capacitors for C511 (two different models of 6.3v 1000µf, one 6.3v 1800µf, one 6.3V 2200µf, one 10V 2200µf), no change. I don't know what I could try now, any suggestions ?

Well, I'm not sure - what's the weird marking by the fuse on that last picture?
Do you have an ultrasonic cleaner? It might be worth giving that end of the board a bath since it's got electrolyte and flux residue all over, at least it was on mine. Scrubbing in IPA should achieve about the same thing though, that's all I did for mine.

Sometimes really perplexing things can happen after cleaning, I was repairing a Toshiba Portege 300CT the other day and had the same problem you now have, after replacing the corroded capacitor & cleaning traces it would only work briefly after warming it up, or if the computer ran for a minute in that broken state it would then start up on the second try. I've left it for a few days and now it's working first time so perhaps something needed to dry out.

I'm planning to get another T1900 laptop so I'll be able to perhaps help more directly soon.

So I did indeed get the T1900C laptop and I'm happy to report it had the same fault you're seeing! It would give the DC fault where the DC light would extinguish and begin to flash as soon as the power button was pushed.
After initial capacitor replacement of the big electrolytics, the fault persisted and the laptop would only power after heating with a hair dryer for a few seconds.

First of all my recommendation is to swap out every one of the 'Elna' brand brown caps since they had all started to leak. You can detect caps that have leaked if you heat the legs of the cap before the board is washed. Sizzling = electrolyte on the PCB, it may also stink of fish.
The ones I had to replace because there leaking were
C511 - 1000uF 6.3v 105c. Height: H10mm & Diameter D10.5mm. Replaced with 10v 1000uF of same size
C521 & C518 & C516 (next to C518) - 120uF 16v 105c H11.5mm D6.5mm. C518 was 56uF but I replaced it all 3 of these with 16v 100uF Rubycon caps w/ H11.5mm D6.5mm
C520 (next to R548) - 56uF 16v 105c H7.5mm D6.5mm. Must be replaced with a cap of same height or less. I replaced with 16v 100uF of same size
C509 - 2200uF 6.3v H20.5mm D12.75mm.

After doing all that, the board would not power up unless heated. So I checked it close up with a torch to look into the board sandwich where that board to board connector is - I spotted some green on the legs of capacitor C63 (33uF 6.3v) on the upper board:

It stunk up the whole room removing that thing. To get these sideways mounted small electrolytic caps off, I found that heating both legs at the same time works best. It's fine to melt the cap body in the process, then using some needle noise pliers twist the body of the cap sideways and it should pop off, taking most of the epoxy with it. Doing it cold results in the cap's plastic body coming off in multiple pieces and leaving epoxy behind.
Then the area was cleaned up with fresh solder, cleaned with IPA and rosin flux removed. I'm using MLCC capacitors for these because they're non-polar and shouldn't degrade / leak - the replacement is a 22uF of some voltage above 6.3v.

Looking at more of them I found that the 10uF 6.3v C526, C527 & C528 on the the lower board's top-side and C523 on the lower side all needed replacing too, they sizzled when removed so they've also leaked, again 10uF MLCC capacitors were put in their place. Lastly C208 (? I got the names from the maintenance manual, it's low-res) on the underside which was 33uF at 6.3v was replaced just to get them all.

After that the laptop has turned on without issue, hopefully your problem is something similar - looking really closely at your pictures, C528 on your board looks just as crusty as these small bad caps on mine did.

Hi @Thermalwrong, thanks a lot for your tests and answers, I'll get new capacitor replacements and I'll test what you did, next episode on next week !

So, I replaced C518-C520-C523-C526-C527-C528, and now it seems to work on both cards ! I'll test on a third card but I'm confident ! Thanks a lot for your tests and your time @Thermalwrong.

That's excellent! Congratulations on getting your ones back up and running 😀

It's got me wondering whether it affects only ones from early in the production run - my T1900C is much older than the T1910CS - or whether these little 'SMD' electrolytic capacitors will all eventually need replacement. I don't want to take my other ones apart again...

Mine (1950CT I got for $1) started working again after replacing all the electrolytic caps. And the next day backlight has died. FML.

Well for that price it's worth fixing, right? 😁

I've recently bought a T2450CT from a seller in Texas where the computer was stored in a hot place and possibly prior to that had many years of use. Perhaps not, it still has Win95 on it and the Toshiba recovery floppy disk images for win 3.11.
There were faulty capacitors on the mainboard so the power supply had a short and would shut down immediately, now working after replacing with some fresh ones and giving the board a ride in the ultrasonic cleaner to get out all the cap juice.
There were faulty capacitors on the inverter board, which were starting to damage nearby traces and those were replaced, the mess was cleaned up with just cotton buds soaked in IPA, now the inverter works.
There were faulty capacitors in the display itself, which also seem to have started to damage nearby traces. Those were replaced like for like - urgh, not great putting SMD caps back in the LCD but I couldn't be sure ceramics would work at the 35v voltage rating. Still don't know if the display works because the polariser has broken down and the LCD panel itself long ago suffered vinegar syndrome and even testing with the front polariser removed I can't see anything and I'm unsure now whether to keep trying with the original TFT or put a 10.4" LCD in there since I have loads of them, but that means figuring out the pinout of this undocumented Toshiba LTM09C012: [SOLVED] Toshiba Satellite Pro T2450CT white screen
The floppy drive's belt had become little chunks of rubber and was starting to corrode the brass pulleys in the drive, that was replaced with one that I 3d printed and now the drive works (which is fantastic, I thought all early Citizen W1D drives sucked)
Oh yeah and the soundcard made some sad noises the first time I powered it up and now won't make sound at all even though the digital side is working. Haven't fixed that yet.

I suppose what I'm saying is, keeping old electronics working can be difficult but it's by no means impossible and with a laptop since it's an integrated system with so many parts, be prepared to fix a second thing after the first thing breaks.
At least the inverter should be an easy fix??? 😀

Thermalwrong wrote on 2024-02-16, 21:05:

So I did indeed get the T1900C laptop and I'm happy to report it had the same fault you're seeing!

Thanks for the report you made on servicing this machine.
What RTC battery replacement would you recommend for this laptop? (T1910)

tibike wrote on 2024-12-16, 14:26:

Thermalwrong wrote on 2024-02-16, 21:05:

So I did indeed get the T1900C laptop and I'm happy to report it had the same fault you're seeing!

Thanks for the report you made on servicing this machine.
What RTC battery replacement would you recommend for this laptop? (T1910)

The RTC battery in the T19xx series is a VG2430 vanadium lithium rechargeable cell, they don't really leak very often and I've found that mostly they still work even now. These shouldn't be replaced with any other cell type than the one removed because the mainboard is designed to charge up that cell, so putting a non-rechargeable CR2032 there could be risky. But you could if you put a pair of diodes (I use 1n4148) going from the battery + to the mainboard + to stop it charging the cell. With the T19xx series there isn't much to set in the BIOS that really requires the RTC battery to work and the original rechargeable cell type will usually retain settings for the day it's used.
Don't replace the battery with a lithium ion rechargeable cell because those require charge management circuitry to keep the voltage in the required range and not go into thermal runaway - the laptop's RTC charge circuit as-is will just float charge the RTC battery when the laptop is on and that's very very bad with a lithium ion cell.

The battery that's AA size and should be removed is the memory backup battery which lets the computer keep memory contents when in standby, they are NiMH and do tend to leak even wicking through the cable so they're best off removed. The standby function isn't too important if the machine's not being used as a portable so much.

The main battery is also NiMH chemistry and mostly those are leaking now with potential to do a lot of damage if the battery leaks into the power board section. Usually I put tape over the main battery contacts so there's a barrier to stop the battery corrosion getting further into the laptop and when I can get the pack open I remove the cells. That's usually a messy job because the main battery welding on these beige toshibas is much stronger than later designs.

Thermalwrong wrote on 2024-12-16, 18:29:

The RTC battery in the T19xx series is a VG2430 vanadium lithium rechargeable cell, they don't really leak very often and I've f […]
Show full quote

tibike wrote on 2024-12-16, 14:26:

Thermalwrong wrote on 2024-02-16, 21:05:

So I did indeed get the T1900C laptop and I'm happy to report it had the same fault you're seeing!

Thanks for the report you made on servicing this machine.
What RTC battery replacement would you recommend for this laptop? (T1910)

The RTC battery in the T19xx series is a VG2430 vanadium lithium rechargeable cell, they don't really leak very often and I've found that mostly they still work even now. These shouldn't be replaced with any other cell type than the one removed because the mainboard is designed to charge up that cell, so putting a non-rechargeable CR2032 there could be risky. But you could if you put a pair of diodes (I use 1n4148) going from the battery + to the mainboard + to stop it charging the cell. With the T19xx series there isn't much to set in the BIOS that really requires the RTC battery to work and the original rechargeable cell type will usually retain settings for the day it's used.
Don't replace the battery with a lithium ion rechargeable cell because those require charge management circuitry to keep the voltage in the required range and not go into thermal runaway - the laptop's RTC charge circuit as-is will just float charge the RTC battery when the laptop is on and that's very very bad with a lithium ion cell.

The battery that's AA size and should be removed is the memory backup battery which lets the computer keep memory contents when in standby, they are NiMH and do tend to leak even wicking through the cable so they're best off removed. The standby function isn't too important if the machine's not being used as a portable so much.

The main battery is also NiMH chemistry and mostly those are leaking now with potential to do a lot of damage if the battery leaks into the power board section. Usually I put tape over the main battery contacts so there's a barrier to stop the battery corrosion getting further into the laptop and when I can get the pack open I remove the cells. That's usually a messy job because the main battery welding on these beige toshibas is much stronger than later designs.

I had no idea what the role of the AA size battery was...
Thank You for the detailed answer!

I am glad I was able to find this thread! I was searching and went through some older esoteric forums that eventually led me here. Thankfully, there are some good, high resolution images of the boards and the capacitors, so I think I can finally get around to restoring my T1960CS.

Is there any guide to actually disassembling the laptop to access the power distribution PCB?

Also, this might be a silly question, but since the PCB is a multi-layer board, how would I go about desoldering the offending capacitors? I assume the leads aren't poking through the other side of the board (or are they?)

Oh, and sorry for the double post (can't figure out how to edit posts; I must be blind as I can't find the button) - for the MLCC that are meant to replace the smaller surface mounted electrolytic capacitors (e.g. C526, C527, C528, C523, etc) - what is the package size that is recommended? They look a fair bit larger than 0805 components, perhaps 1206?

Darkblade48 wrote on 2025-01-18, 01:24:

I am glad I was able to find this thread! I was searching and went through some older esoteric forums that eventually led me here. Thankfully, there are some good, high resolution images of the boards and the capacitors, so I think I can finally get around to restoring my T1960CS.

Is there any guide to actually disassembling the laptop to access the power distribution PCB?

Also, this might be a silly question, but since the PCB is a multi-layer board, how would I go about desoldering the offending capacitors? I assume the leads aren't poking through the other side of the board (or are they?)

For the disassembly manual, check out the full maintenance manual - https://www.minuszerodegrees.net/manuals/Tosh … ce%20Manual.pdf
The main cap that should be bad on the T1960 will usually be C511 which is 6.3v 1000uF.

Removing the caps isn't too tough, the ground plane isn't like an ATX motherboard. For the through hole caps, heat one leg at a time and rock the capacitor out, continue til it comes out then use a desoldering tool to clear the holes. Solder braid is another option but there are lots of components very close where the capacitor legs are so it could make a mess.
The little box electrolytics just put some fresh solder onto both legs then assuming your iron tip is big enough heat both legs at the same time, wait a couple of seconds then use needle nose pliers to twist the box of the cap away from the mainboard - the heat should loosen the glue and it should come off cleanly. Then clean up that area and install the MLCC caps.

Darkblade48 wrote on 2025-01-18, 07:57:

Oh, and sorry for the double post (can't figure out how to edit posts; I must be blind as I can't find the button) - for the MLCC that are meant to replace the smaller surface mounted electrolytic capacitors (e.g. C526, C527, C528, C523, etc) - what is the package size that is recommended? They look a fair bit larger than 0805 components, perhaps 1206?

Yeah, checking with calipers against one of these smd electrolytic caps it seems 1206 is about right. I wasn't specific because the caps were salvaged off of newer scrap boards so the sizes are all over the place. If you're purchasing caps then something in the range of 1206 to 1812 (inch sizes) seem to be the best fit to replace these small 'box' electrolytic caps.

I'm not sure that the T1960 has all of caps that can be bad on the T1900 though so it'd be interesting to know what you find. It looks like the T1960 doesn't have that cap that went bad on T1900 on the upper CPU board.

Great to see that this topic is still watched by you, Thermalwrong! I have this page open as a permanent tab in my browser, at least until I can figure out how to fix my old laptop. I also can't seem to figure out a way to set e-mail notifications (so that I'll get notified when there is a reply), but I refresh this tab at least daily to see if there are any updates 😀

Thermalwrong wrote on 2025-01-18, 16:09:

For the disassembly manual, check out the full maintenance manual - https://www.minuszerodegrees.net/manuals/Tosh … ce%20Manual.pdf
The main cap that should be bad on the T1960 will usually be C511 which is 6.3v 1000uF.

Perfect, this is just what I needed. It looks comprehensive and fairly straightforward, all things considered. Looks like the hardest part might be a) keeping track of all the screws and b) prying the keyboard retaining tabs without breaking them.

Thermalwrong wrote on 2025-01-18, 16:09:

Removing the caps isn't too tough, the ground plane isn't like an ATX motherboard. For the through hole caps, heat one leg at a time and rock the capacitor out, continue til it comes out then use a desoldering tool to clear the holes. Solder braid is another option but there are lots of components very close where the capacitor legs are so it could make a mess.

Good to have these tips. I wasn't sure if the caps were indeed through hole, as the reverse side is a mess of solder joints and other components. I'm used to working on old audio tech (tape decks and Walkmans), and they usually have well laid out electric diagrams as well as PCB layouts 😉

Thermalwrong wrote on 2025-01-18, 16:09:

The little box electrolytics just put some fresh solder onto both legs then assuming your iron tip is big enough heat both legs at the same time, wait a couple of seconds then use needle nose pliers to twist the box of the cap away from the mainboard - the heat should loosen the glue and it should come off cleanly. Then clean up that area and install the MLCC caps.

Yeah, checking with calipers against one of these smd electrolytic caps it seems 1206 is about right. I wasn't specific because the caps were salvaged off of newer scrap boards so the sizes are all over the place. If you're purchasing caps then something in the range of 1206 to 1812 (inch sizes) seem to be the best fit to replace these small 'box' electrolytic caps.

I'm not sure that the T1960 has all of caps that can be bad on the T1900 though so it'd be interesting to know what you find. It looks like the T1960 doesn't have that cap that went bad on T1900 on the upper CPU board.

Yep, I don't happen to have any scrap boards, so I'll probably be putting an order through Mouser in the upcoming days/weeks. I might as well order everything that might possibly need replacement (thanks to your very detailed, annotated diagram). 1206 (inches) sound good. Might just order 10x of a few package sizes in 4.7, 10, 22, 33 and maybe 47 uF since they're like 5-8 cents each anyway; who knows, they might be useful for future projects.

Oh, and I managed to forget another question that I had.

I don't seem to be able to find my original charger, and based on what I could find, the original was just a 15V, 6A charger? I suppose anything that meets those specs should be fine?

That will blow the fuse and/or the laptop will not start. You need 18v at 1.7a.

19v is also fine but the power supply must be limited to less than 1.8 amps, going over that with the battery fitted risks blowing the fuse because of how charging works on Toshiba laptops through all of the 90s - they whack max current into the battery when you plug in the charger and it uses that to determine if there's a power fault. If the current is too high the laptop will either go into a power fault mode which is where the power microcontroller shuts off power to avoid damage. Or the fuse will blow and you'll have to replace it