Navigating the IBM Thinkpad 760 series to restore or repair

[solidpro]

Hi

This series has got to be one of the biggest minefields when it comes to model-naming and slight variations in build and specification making it quite difficult to nagivate through a repair or refurb. Maybe this could become a sticky 760 repair thread?

A list of the first things I'm aware of:

- Whilst the 765 is considered part of the 760 family and whilst shares a similar design, it's chassis is completely different to the 760-series and therefore the screen and internal layout is bigger and not interchangable.
- The complete memory configuration changed many times:
- 760C, 760CD, 760L, 760LD = 88pin EDO - hard to find.
- 760E, 760ED, 760EL, 760ELD, 760XD, 760XL = 144pin EDO - common.
- If you put the memory daughterboard from a 144pin machine in a 88pin machine you just get a white screen when powering up.
- "all L models did not have Mwave audio, using ESS 1688 Audiodrive instead"
- Hot take - L models were 'consumer' end models of this business-end laptop.
- CD models have nothing to do with having a CD-ROM drive, altbough D mostly means the case is built to accomodate one (apart from the EL, ELD and XL which also have the case to accomodate a CD-ROM drive!)
- All models have a timebomb hibernation battery built into the palmrest
- If you attempt to remove the hibernation battery, the PCB it's connected to contains 4 connectors - 2 to stereo speakers, 1 for CMOS and 1 for hibernation. These connectors are exremely brittle and I've found it very risky to do anything other than snip off the hibernation battery wires because trying to move the board often creates more problems.
- Many keyboard have a '08611' trackpoint error, which I have not found a fix for, despite not using the 'timebomb' pencil-erasor style trackpoint nub
- There was no CDV model
- 760C and L have a smaller case, much more similar to the 755.
- All keyboards are interchangable (with exception of 765 which has a wider palmrest)
- DSTN screens were available but rare - be careful if buying an EL model as these had the DSTN option.
- There were at least 3 types of TFT in 10.4", 12.1" and 13.3" variations, with later 12.1" and 13.3" displays offering XGA. 13.3" screen will only fit inside the larger 765 chassis, so all 760 model machines have a maximum size of 12.1"
- Floppy drives are very similar to 355/360/370/755 floppy drives but have a weird plastic slider down the right side - seems like a 'spacer'.
- Hard drives *I think* are interchangable with 355/360/370/755 with the 'regular' 760 models but not the slimmer 760C variants - because they're too fat.
- Simlar to the 770, I've found the TFT screens can succum to a degradation around the edges - a flourescent cloud that shows up on black screens.

I'll edit this as I go, or add on new stuff as I'm tearing down more this weekend.

[solidpro]

I do have this question to put out there. One of my 760s has an additional mini-din style connector on the side. I can't see this mentioned in any specification...

Does anyone know what this connector is and what model I'm looking at? I can't trust the LED panel badge on these anymore. It came to me badged as a CD but I don't think it is because the CD is relatively common and my other CD machines don't have it.



There is a telephone symbol next to this space on all 760 machines suggesting some models had a modem here, but it doesn't look like a modem port. At some point the machine will be given a teardown again but I'm trying to do as much homework before I start!

[axur-delmeria]

I don't know what that port is, but on my 760XD, that area had the RJ-11 port for the MWave-based audio and modem card.

[solidpro]

Hmmm.... the plot thickens! I would understand an RJ-11 because it's been noted elsewhere that US models had a modem for IBM support, but this thing is a bit like a video connector of some sort....

[panips]

Interesting, I never noticed that IBM had some mini din 9 connectors.
This one is widely used in some PC/98 series laptops, I cannot remember exactly the 9pin/8pin which one is for Analog VGA and which one is for the bus mouse. But if it comes with the VGA logo, I assume you can find a mini din 9 to d sub vga cable. Or you can just use some jumper cable to test, it's pretty straight forward pin mapping thing.

[solidpro]

*ah*

[ThinkDan]

I knew I recognised it but it took some head scratching to find the details. Thanks for an entertaining diversion

It's the external DAA Telephony Kit connector. DAA = Data Access Arrangement.

This means it's an Mwave equipped model (760CD, 760ED, 760XD) that was sold in a country for which the standard internal telephone jack connector was not approved, hence it was supplied with a blanking plate rather than modem socket. My recollection was that the DAA box arrangement sidestepped some country certification problems that would not /could not approve the internal phone jack arrangement more commonly seen. I can't now find a list of which countries those were!



Here's a page from the 760 online manual that explains how to install the DAA Kit, with pictures.

There was a lab in Greenock which dealt with such things, they had a PSTN hardware emulator that could emulate the telephone system in many countries. I used to visit occasionally when we received odd queries into the HelpCentre about specific country connector plugs, dial tones, and such like. Sometimes you just had to see and hear it!

If you look on the label on the bottom of an Mwave-equipped 760, it should show a number of telephony certifications along with all the other FCC, CE, etc. regulatory certifications.

The standard 'internal DAA assembly' block is visible in the HMM as index 31 in the common parts listings (exploded diagram), and images of the part can be found easily by googling for FRU 12J1571, e.g. currently this ebay auction. As you see it just plugs into the end of the Mwave board within the TP760. The 755CD/CE/CX etc. models had a similar arrangement.

It's an interesting curio but useless without the external box and cabling.

[solidpro]

Ahhhh, that makes perfect sense. In another life I would have been capable of building a PBX to act as the carrier and simulate the different voltages, dialtones and wiring so maybe they would have given me a job. Thanks for doing the homework - if only I had the DAA box and cables and then it really would be useful

I've ended up with 6 full size machines, which later today will become two 'as perfect as I can make' XD machines and some middle-standard other variants which will be sold.

[solidpro]

Some more notes.

I hadn't noticed this before but SVGA and XGA models have different thickness of lid!!

There are two types of 12.1" TFT lids which support the two very similar but different SVGA and XGA LCDs:

1) SVGA Lid/LCD:

It's thicker but will fit all 760 models.
SVGA LCD has a different mainboard connector to XGA
Has a longer LED panel which slots into the back of the keyboard

2) XGA Lid/LCD:

Thinner than the SVGA lid but will fit all 760 models
XGA LCD has a different mainboard connector to SVGA
Has a shorter LED panel which slots into the back of the keyboard

Connectors are keyed differentl and will not fit to the opposing connector:





The lids I disassembled have two types of hinge, using a slightly different but very similar design. They're bolted down slightly differently and not interchangable:



Finally, whilst all the screw standoffs are in the same place, meaning you can physically swap different TFTs between different lids and bezels, the standoffs are different depths, and the LCD bezel itself is different (one has to be shallower). So basically don't bother trying to swap SVGA and XGA panels between lids.

I also discovered 3 different lid design for the 2 types of TFT panel - one has 6 screws at the base underneath two strips of black plastic stuck down over the top.

[fatkatsupra1]

thank you for sharing your teardown work! 760s rule!

[ThinkDan]

Just to add, a 760 External DAA kit has just popped up on eBay:

[artus]

Good day to everyone,

I recently got a 760ED, it was the first computer I had in 1998. It’s a lot of nostalgia. I want to let it the closer to new that I can, so I got another 760e to use the better parts of the two. My question now is: is it possible to upgrade the screen of a 760ed to xga? I already got the xga connector, the new screen and the xga card, but I want to use the svga lid of the another 760, the e one, because it’s in much better condition than the ed one. Hope someone can help me with this. I want advice before going to dissemble the screen.

[solidpro]

If they have the same lid connectors, it should be a straight swap. See my pics above showing the notch differences between SVGA and XGA connectors.

[Luizapper]

...
- Many keyboard have a '08611' trackpoint error, which I have not found a fix for, despite not using the 'timebomb' pencil-erasor style trackpoint nub

This 08611 error occurs (in my 770 case) when trackpoint is somehow stuck and needs cleaning due to grime and dust accumulated through the years. Using contact cleaning spray on base of the stick (removing cap and square plastic in between) has solved this issue.