T22 powerup problem

[Timoti]

My newest sick puppy just arrived: T22 with power up issues, old owner says it's a mobo problem.

Symptoms: after pushing the power button, fan spins, LEDs look like a normal power-on sequence on my T20, power LED stays on, no backlight, no display on LCD, nothing happens.
Without RAM it beeps the 1-3-3 pattern, otherwise it's the same.
Tested without miniPCI device, ultrabay device and HDD, 128MB module tested in my T20.

I replaced the following components with known working ones, still no effect:
-CPU
-fan
-LCD assembly (panel&inverter)
-battery
-CMOS battery

After testing the T22's LCD in my T20, turned out the backlight was dead (replacing inverter didn't fix it), but the display itself was okay.

Any ideas on this one?

[truk]

Sounds like the original owner was right, but you may want to try booting off an external monitor and testing different combinations of the battery and power adapter.

[Robbyrobot]

After testing the T22's LCD in my T20, turned out the backlight was dead (replacing inverter didn't fix it), but the display itself was okay.

How about the LCD cable? You might try swapping the entire working display from your T20 into the T22. If you then get an image on the screen, you'll know you've just got a bad cable. If the screen is still dark, the fault lies elsewhere.

I'm presently working on a T21 with a dead backlight not due to the display (screen, cable, inverter), and am thus in a similar position to yours.

[Timoti]

I did swap the entire display from the T20, nothing. Same with the external monitor.
Guess I should try Ray's corner-twisting method next...

[Robbyrobot]

I did swap the entire display from the T20, nothing. Same with the external monitor.

No picture on the external monitor either, eh? In my case, the external monitor works (more or less). My suggestion would be to reseat the mainboard connector to the I/O board (the small white connector on the bottom side of the board near the CPU and next to the large black connector for the port replicator), since this appears to be a weak spot, at least in my case. Then check again whether you get an image on an external monitor.

[Timoti]

Still no luck, after cleaning and re-seating the mobo 2 times...
Found a little white looking grease or something on the underside of the board, but still nothing after cleaning.

I tried with all combinations of battery/AC, and the battery seems to charge when plugged in AC (blinking battery LED).

Anyways, thanks for the tips everyone!

[Robbyrobot]

Found a little white looking grease or something on the underside of the board...

That's traces of the thermal transfer paste that you have to put between the fan and the CPU die. Sometimes it's white, sometimes silver colored. Be sure not to forget it when you reassemble the machine.

As for your - and my - main problem, I have no better ideas at the moment. If I can think of anything else, I'll let you know.

[Timoti]

I'm pretty sure it wasn't thermal paste, it was more like some white dust. Anyways, it's not there anymore and it produces the same symptoms.

But i've got an idea: my friend has a T20 with the 0175/CRC1 problem. What if I de-solder the flash IC from the T22 board, and re-solder it on the T20? That would give me a good board, and one even more dead. Anyone done it before?

[Robbyrobot]

But i've got an idea: my friend has a T20 with the 0175/CRC1 problem. What if I de-solder the flash IC from the T22 board, and re-solder it on the T20? That would give me a good board, and one even more dead. Anyone done it before?

The EEPROM is about the size of a grain of corn (5x4 mm), is SMD and has 7 pins on each side. Unless you're quite an electronics professional with good equipment your chances of desoldering this component and putting it on another board are very close to zero.

In addition, the content is not necessarily identical from board to board, and certainly not from model to model, although the same EEPROM may be used for various models.

There are places you can pay to have the CRC1 problem corrected by reprogramming the EEPROM. That is definitely easier than trying to switch SMD components from board to another - and works - but is still not trivial.