Help Restoring a GRiD Compass 1101

[fargo]

Hi everyone,

I recently received a GRiD Compass 1101 from a seller who told me that it powers on and that the LCD displays a checkerboard pattern.

Upon receiving the computer, I noticed debris falling from it and heard rattling sounds inside. I removed the top lid and found severe corrosion on one of the monitor hinge bases. I then removed the PSU board and the two upper boards, and unfortunately found heavy battery leakage. The battery was completely disintegrated, and its liquid had attacked every piece of metal in its path. The damage to the bubble memory module shown in the photo appears to be limited to the outer shell, and fortunately the contact pins are still intact.



I cleaned the board as much as I could using IPA, vinegar, and rust remover.



I now want to flip the motherboard over to inspect the other side. The problem is that I could not find a maintenance manual for the Compass 110x series, and I have not been able to figure out how to remove the monitor and keyboard in order to access the motherboard fasteners.

I’m hoping someone here who has experience with these computers can guide me on how to remove the monitor, preferably without releasing the spring tension, and also how to remove the keyboard safely.

Thank you!

 

[JDat]

There are lot of things to do. Let's start one by one.

Disassembly?

Sorry, guy in video is speaking in russian, but... just watch video slowly.

 

[fargo]

Thank you so much for the video, @JDat. I was able to remove the motherboard after drilling out one corroded screw and literally chiseling around the left hinge base!

Fortunately, the case and the hinge base took most of the damage.



The motherboard also has some damage, and I hope someone can provide high-resolution photos of the motherboard, preferably 1983 Rev. C, especially of the marked damaged areas.

 

[JDat]

Ahh. Rev.4 board (with ASIC)...

Anyway... photo from Rev.3 board.

I don't have schematic for Rev.3 board (yes, I am lazy and still in process of beeping wires), but I am quite familiar with 1101 internals and hardware on main board. Just ask, I'll try to answer.

 

[fargo]

Thank you again, @JDat, for offering to help. Yes, it is marked “Main Logic 4,” and it is “Rev. C” according to another marking elsewhere on the board.

Three capacitors came off the motherboard due to the battery leak: C25, C1, and C12. I’m also not sure whether “CR1” (a diode?) was originally populated or not.



I found this small piece floating inside the case. At first, I thought it was one of the serial/accessory port pins, but when I checked, all of the port’s pins were intact. I’m not sure what this could be.



I still need to clean the area around the left hinge more thoroughly. I’m doing the cleaning very gently so I don’t damage any traces or pads on the board. I’m also confused about these resistors, as my multimeter gives me different readings when measuring them from both sides of the board. The board looks like a 2-layer board to me, but I could be mistaken.

 

[JDat]

Diode most probably is for RTC Clock IC. Check RTC datasheets attached.

Clean up all mess. Check VIAs on PCB.

 

[JDat]

Here is incomplete and unfinished 1101 Rev.3 schematic made by @Conventional Memories and me.

Diode CR1, according to Rev.3 photo belong to RTC. Two diodes CR2 and CR3 are for Bubble memory according to incomplete schematics.

 

[Istarian]

That little piece looks like a glass encased diode (probably either germanium or silicon) to me. I can sort of make out a blank band on the left side and some black text that reads "?263" (? signifies symbol that's hard to make out).

 

[NeXT]

My guess is a 1N6263 schottky diode, based on marking alone. Could be wrong though but that certainly won't be Germanium.

 

[JDat]

I don't have super high resolution mainboard photos of 1101 Rev4, but I have 1109 photo with OKayish quality. Diode CR1 is near U14. Logically check U14 datasheet! Check my 1101 Rev.3 schematics and you can logically understand where CR1 is connected. Don't trust my schematics? Go to bitsavers and find Intel bubble development documentations and APP notes (huge PDF scans). CR2 is located near 7220 Bubble controller on 1109. On 1101 Rev.3 it's also located in Bubble storage region. To make sure, also so some wire beepings with multimeter and find where CR2 is connected. Compare with my schematics, compare with Intel Bubble documents

My conclusion: CR2 is a part of bubble memory stuff.

On 1109 CR4 is located near U76, RTC chip.

BTW, by unconfirmed information 1101 Rev.4 mainboard is the same as for 1109, if we not take into account difference in DRAM memory.

Just keep digging, slowly and steady with a lot of patience, and you'll find enough information to repair your Compass!

PS: Can't upload 1109 mainboard photo, because .jpg file is too big for forum (14.1 MB)

 

[fargo]

Thank you all for your input. The corrosion is severe. I tried tracing some connections today, but almost no pad in the leakage path is conductive. The solder mask on the PCB under the leakage has become very thin, and even slight scraping removes it and exposes the traces. I have to be extremely gentle so I don’t accidentally damage any traces.

I also failed to extract the remains of the corroded pins from the board. The solder on the board is badly corroded and would not desolder, even after adding plenty of flux and fresh solder. I’m not giving up on it, though, and will keep trying to repair it.

Does anyone know the PSU connector pinout? That would be very helpful to have.

 

[fargo]

PS: Can't upload 1109 mainboard photo, because .jpg file is too big for forum (14.1 MB)

Could you please upload it here: http://uploads.linkpc.net

After you upload it, I’ll make a smaller forum-friendly version and also share the full-resolution image link here, since it may be useful for others too.

 

[NeXT]

When I had to deal with battery leakage on a GRiDcase 3 I had to do a full strip of the machine to wash all the panels. The inside of the magnesium case got a steel cleaning brush and the board took a plastic bristle brush and both got a wet scrub and hung out to dry for a day before the interiot of the case got a spray of black paint to protect the magnesium. If you look on yours the battery damage is evident underneath by the spidering in the paint where it ate completely through.

 

[JDat]

Does anyone know the PSU connector pinout? That would be very helpful to have.

Once I made quick test on my 1101 Rev3. I assume it's the same for 1101 Rev.4 and 1109

PSU Pinout:
When looking from front of Compass (lid closed)
 1. -5V
 2.
 3. +15.2V
 4. GND
 5. GND
 6. GND
 7. +12.6V
 8. +5.1V
 9. +5.1V
10. -12.2V

 

[JDat]

Could you please upload it here: http://uploads.linkpc.net

What a stupid service, so, no, I can't! But... Here you go by using file exchange service in my country...

https://failiem.lv/u/ec7qyyynec

 

[fargo]

Thank you, @NeXT. That is very helpful. I did notice the spidering in the paint underneath, so the leakage clearly reached farther than I first hoped. I think you are right that this needs a full strip-down and a proper cleaning of the case panels, not just the board area.

I’ll continue cleaning the magnesium case carefully, and after removing the remaining corrosion I may also repaint/protect the affected area so it does not continue to deteriorate.

Thank you, @JDat, for the PSU pinout and for uploading the photos. That is exactly what I needed. I’ll compare the pinout and the photos with my board, especially around the damaged/leakage area, and report back what I find.

 

[fargo]

What a stupid service, so, no, I can't!

Sorry about that! I set up the service to help with the image upload, but since the link is posted here publicly and points to my homelab server, I added the 1 upload per hour limit as a basic security measure. I assumed you only had one image to share.

 

[JDat]

1 upload per hour limit

That was a problem. I didn't send even one, but anyway... Just sarcasm and... Files reached destination somehow, that's most important.