If the main battery was still in this shape it had to be the "Standby battery".

Removing the topcover with LCD assembly revealed the first loose broken piece as you can see on this picture. 😠

For the rest the notebook was still looking pretty neat:

Carefull tilting it on one side revealed two more small plastic clips broken off on the right side where the add in card is missing. All parts will be glued or epoxied back into the chassis.

After removing the keyboard the harddrive and floppy drive showed up looking like this:

At this point I noticed some blue spots at the bottom of the machine between the floppy drive and chassis that warned me something bad was happening there as you will see further on.

To remove the floppy and harddisk it was necessary to remove the processor board first, and after removing all screws and lifting the board out it looked still pretty neat. 😎

Topview of the processor board showing the video/power&I/O board below it:

Underside processor board:

I have no Idea what the sticky stuff on some chips comes from. It's just as on the chipset IC you can see here:

Sanyo chip also has it on the surface:

The rest remaining in the chassis:

VGA and powerboard info:

To be continued in the next post..

I had great interest in the power section on the bottom board, knowing that the Thinkpad 300 was manufactured by Zenith and in being made there every unit had to be repaired first prior to being sold.. contrary to the Thinkpads that later followed this model. 🤣

This unit has clear traces from re-work done on the unit.
Powersection:

Utter left part with the cooling rib:

The part below the caps in bottom of this picture clearly is soldered on afterwards:

The part with the MA753 also is soldered on afterwards:

"Cooling fin"

And the flash chip in detail next to the chipset:

Continued in the next post again..

Now the motherboard left the chassis it was time for the harddisk to be removed. The few times the notebook actually started a bit the drive made a severe knocking sound so I assume it's heads are stuck or crashed. 😵

Top view of the harddisk:

Conner harddisk after removal:

I haven't had time to test the harddrive on my testbench, will do that as soon as I have the time for it.

The floppydrive also come out good after removing one screw:

Notice there is some blue dirt on it in the mid right section.. because below it:

The source of the aroma and the blue dirt everywhere clearly was an overaged and severely leaking standby battery:

It was an huge pile of acid mixed with eaten plastic parts and dirt 😵 😢

So time for damage control now!

On the connector on the powerboard there is a bit of blue goo visable:

Compared to the bottom chassis luckily it looks not that bad 😵 :

First step was removing the battery, so I grabbed a plastic bag to throw it in and carefully removed it. The thing was glued to the bottom and it needed a lot of force to let go so I used a big wide spatula to make sure it wouldn't break in pieces. The result:

The connector on the motherboard seems okay, the blue is a marker and not from the acid:

I put some small pieces of cloth in the chassis on top of the leakages which are drenched in neutralising fluid. On top of that are some rock pieces, and hopefully tomorrow most of the goo is gone or atleast neutralised.

Since I can't continue any further I took two more close ups from the powersection where the solder work is better visable:

Solder work on both those points doesn't look very neat so I hope the system works again after assembling and finding a new decent Standby battery.
I hope you guys forgive the shitload of pictures but it was a nasty start to get this old 386sl system running again!

I started searching for a new battery but a real drop in replacement ain't available and since the height under the floppy drive is very limited I have to look what might be possible to replace it with. Any suggestions are welcome since some here will have more experience with that. 😊

I came a bit further today. The bottom case lost alot of it's acid stuff due to a mixture of lemonjuice, soda and deminiralised water. However, it still looks far from perfect. 😒

Any suggestions on how to further reduce the amount of residue in it or is the only thing I can do is paint it over to hide it? Looks awfull like this and would appreciate if it could be turned into a much neater piece.

I also glued some of the broken off parts in it again, they all seem to hold great after 24 hours of drying so atleast one good succes so far.

Any feedback on how to treat the acid damage on the plastic is welcome 😲

IIRC Apple Cider Vinegar also works well as an anti-acid (or is it white vinegar?) but ya since it sounds like you have already taken steps to neutralize the acid a couple coats of primer paint/spray paint and a coat or two of normal paint would clean it up real nice and cover the damage up.

Nvm1 wrote:

Any feedback on how to treat the acid damage on the plastic is welcome 😲

Love this rebuild, interesting note about Zenith build quality, thought they had a reasonable reputation? Look forward to more pics 😀

In re paint damage, I have a Mac Powerbook with similar looking acid damage, but despite soaking the whole case bottom in white vinegar (few litres in a plastic tub), it dissolved some crud, and loosened up some of the damaged paint, but left a mottled finish. My guess is, seeing that the paint on your 300 has been eaten away to metal, that you'll need to prime and paint as suggested. However, given you need to dig deep to even see the damage, don't worry too much about looks, the laptop looks great externally!

Well, minor update. Whatever I tried didn't revive the Conner IDE 85mb drive without opening it so I am gonna try to open it up this evening and see if I can get the head moving again. 😵

I also got a spraycan paint, according to the shopowner it should stick well to the surfice without using primer. Gonna test it a part of bottomcase. Hopefully it will go black and stay black for a long long time... 🤣

Edit:
The Conner drive is alive again! Opening up and carefully forcing the arms to move brought it back alive. I had to move it quite a lot up and down to make the head move "freely" again (you can feel the magnets pulling it back to one specific resting point nevertheless). After powering it on again it didn't knock and was completely recognized as a drive again. Sadly I couldn't do a surface test since the USB to IDE converter doesn't understand the C/H/S addressing of such an old drive correctly. 😀 But I will test that later this week with an old P1 or 486. Really happy that this operating was a success and not a single bit of dust got into the drive. 🤣

Another round of updates:
I went on and used my dremel to remove most residue on the surface of the bottom cover. It resulted in lots of blue dust flying around. The big spots still looked awfull, the small points all over the base got cleared completely this way. 😀

The bottom after grinding it with my dremel:

The bright spots are the places where the acid was spread across the bottom. In the small spots it was completely removed after using the dremel

The big spots remained and still looked awfull:

So after this I used a brush to remove all dust from the cover and I went on the spray it in two runs.
The first run:

The outlines of the affected spot stay visible through the paint.

The second run:

Now the whole looks alot better already. Tricky part was the area around the floppy entrance:

In the meantime I received a new 20mAh bios battery which I hope will serve as a replacement bios battery for the Thinkpad:

It has the wrong connector but the correct connectors are already underway from China 😀

After a day of drying I started reassembling the bottom part as far as I could:

Things to do next:
- Test the HDD in my old P1 system
- When the connectors arrive solder it to the battery and connect
- Rebuild the whole system and test it
- Find and install 387sl
- Try to find extra RAM
- Try to find the expension Network card 😳

Nvm1 wrote:

The source of the aroma and the blue dirt everywhere clearly was an overaged and severely leaking standby battery:

Very interesting project! I am in the same position with a Toshiba T1600 286 laptop - fortunately the standby battery in this model was housed in a plastic chassis, separate from the rest of the case. I just don't know yet if the corrosion has found its way back to the PSU circuits (it looks fine so fingers crossed). I just received my new BIOS battery the other week, so time for some open-case testing! Good luck.

brassicGamer wrote:

Nvm1 wrote:

The source of the aroma and the blue dirt everywhere clearly was an overaged and severely leaking standby battery:

Very interesting project! I am in the same position with a Toshiba T1600 286 laptop - fortunately the standby battery in this model was housed in a plastic chassis, separate from the rest of the case. I just don't know yet if the corrosion has found its way back to the PSU circuits (it looks fine so fingers crossed). I just received my new BIOS battery the other week, so time for some open-case testing! Good luck.

If the standby battery is in a separate housing then usually the damage is minor. Just post your progress as soon as you start with it.

I went on with my own rebuild since I received the Dupont connectors from China:

Used a soldering station from work to do the soldering.
In progress:

Ready:

Before I did build the bios battery into the chassis I put five layers of see through tape around it to shield it from external causes and the notebook itself from another leaking battery 🤣

The end result looks like this:

Now I have to find time to rebuild the notebook further 🤣
Things left to do next:
- Test the HDD in my old P1 system
- Rebuild the whole system and test it
- Find and install 387sl
- Try to find extra RAM
- Try to find the expension Network card 😳

I found some time to build the Thinkpad 300 together until it looks like this again:

Positive news is that the Harddisk runs like a champ again! Another succes.
However, after giving in the correct time and date again the screen seems to have an issue.. It starts out like this:

Pretty bright and very readable.. just a few "dancing" lines in it. But after 10 minutes it looks like this:

All contrast just disappears.. 😠

The backlight still works well, it's just as if all contrast fades in 10 minutes away. So I opened the screen and started searching. In the pic below is on the left side the inverter and backlight and on the right side the control board for brightness an contrast.

After closer inspection it seems that the aluminium caps on the control board all leaked minor or major and left black sticky stuff on the board. As example the cap in the middle and the black sticky stuff below it.

Now a question to some more experienced people here. Would it possible be a solution to remove all existing caps and replace them so that the contrast keeps well?
Or am I quessing in the wrong direction? 😕 Any help would be great. If needed I can make some more detail pics of the board.

Nvm1 wrote:

Now a question to some more experienced people here. Would it possible be a solution to remove all existing caps and replace them so that the contrast keeps well?
Or am I quessing in the wrong direction? 😕 Any help would be great. If needed I can make some more detail pics of the board.

I have a similar problem with my Toshiba and have been advised to:

- remove all caps
- clean up
- test traces and vias in the affected area
- replace caps

With a machine this age it seems to be the only way to go if you want it to live for longer. If there is no damage and the caps are replaced it should work good as new.