After the Falcon arrived, it showed the typically symptons of a dead NVRAM Chip Battery. The internal clock was skewed up every boot. To ensure that the Falcon will work properly it has to be changed.
The following instruction is given WITHOUT ANY WARRANTY of success. You might damage your Falcon irrepairable!
The replacement chip is a DALLAS DS12887A. In germany it can be ordered from Reichelt electronics.
Because the original DALLAS chip fits exactly under the lower shielding it will be hard to replace the chip with a new one and a socket. But soldering the new chip directly to the board is no option here, because in a few years,when the battery in the new chip is going to die again, it has to be easy to change. For this reason i’ve ordered a “low-profile” socket from Reichelt, too.
Tools and other stuff
- A soldering iron with a fine round needle (1 – 1,5mm)
- Desoldering braid
- Solder (Sn 60, Pb 38, Cu 2)
- multifunction rotary tool with cut-off wheel
- Small caliper
- Perhaps a needle for cleaning the pin holes.
Doing the job
First we have to remove the old chip. Desoldering all pins at once and then removing the chip is no option, as the board quickly absorbs the heat. The best option in my opinion is to desolder one pin at a time and remove it with a caliper.
So i removed the chip carefully by using a multifunction rotary tool. Cut parallel to the pins and then parallel to the board to remove the upper part of the Chip. Be careful not to damage the GALs left to the chip (look at the left Chip on the picture above. One of the preowners had damaged it slightly by trying to remove the NVRAM chip with a screwdriver or something similar).
After the upper part is removed (where also the battery fits in) you may take a look on the chip and all we have to do now is to remove the middle part of the remaining NVRAM chip part.
Try to get some help and have somebody to hold a vacuum cleaner near the multi tool as it oterwise might become very dusty 😉
Be carefull not to cut the board!
Now you can break the inner chip from the pins…
… and easily remove it …
And after a little bit of cleaning up, you can access each pin seperately to cleanly desolder them.
No need for the old chip any more 😉
Desoldering each pin with desoldering braid and removing the pins is now an easy job which will take up to 20 minutes maximum. You can now insert your socket and solder it firmly to the board. Pay attention to cold capillary joints.
Even better 😉 But i suspect the chip + socket will be a little bit to high for our shielding, even it is a “low-profile” socket.
From this time on I have forgotten to take pictures (sorry!), but I needed to cut off the shielding where the DALLAS chip sits. Best, use a small metal saw, but be carefull, the rest of the shielding is very unstable and may get deformed. So don’t be to rough!
Once reassembled, the Falcon boots up normally …
… and keeps the time i’ve entered in the Control ACC. I don’t even need to reinitialize the NVRAM up to this point but i decided to reset it, so that further settings saved to the NVRAM will not end up in a data nirvana.
I used NVM_CONF by Manuel Hermann, which warned me at startup that the NVRAM is unreadable and has to be resetted. After a reboot everything seems ok and i’m quite happy that the falcon returned to normal operation.