After short time my Roomba would no longer dock correctly. It tried docking but did not seem to detect the docking station/home base. However when plugging the charger directly into the Roomba it charged correctly. Here I will show the process of finding the fault and fixing it.
Checking around on the web, I found no one with the same behaviour, and questioning around on www.roombareview.com/chat neither gave any solution. However after posting my problem in the forums, I got some very valuable help. Here is the thread:http://www.roombareview.com/chat/viewtopic.php?t=10350&highlight=
The following video shows my Roombas behaviour:
Testing the home base
I had already tested the Roomba towards another Homebase to verify that it was my Roomba and not the homebase that did not work. Just to be absolutely sure, I also tested my home base using "Gordon"s tip from the roomba review thread linked above: Connect a resistor of 4k7ohms (color code yellow, Violet, red, can be bought at your local Radio Shack or similar store) between the two charging pads on the home base, and measure the voltage over his resistor. The voltage will rise to appx 22.5V if the homebase works correctly.
As the space between the charging pads are greater than the length of standard resistors I found the simplest solution was to insert the resistor into the voltage meter plugs, and the inserting the test leads. This way you don´t need to add wires to the resistor to get it to reach over the gap between the charging pads, but can instead use the test elads to simultaneously connect the resistor to the pads and measure the voltage. See images below.
Now by touching the Roomba charging dock connectors with the test leads of the voltage meter you can easily test that the charging dock works. You will see the voltage rise to approximately 22 volts DC, and the charging light on the dock lighting up.
If the voltage is much lower than 22V and/or the charging light does not get lit, your dock is damaged and should be replaced or fixed.
Dismantling the Roomba 560
Second step was to dismantle the Roomba. Strictly speaking there was no need of removing all components, but as I was unsure of what the problem was, I decided to pull everything apart. See also image gallery in the end of the article.
Step 1: Remove the four screws holding the bottom plate.
Step 2: Remove the battery.
Step 3: Remove the brushes and suction chamber.
Step 4: Remove the three screws holding each wheel/motor assembly.
Step 5: Remove the screw holding the sidebrush motor.
Step 6: Remove the 10 screws holding the bumber parts together.
Step 7: Remove the bottom part of the bumber
Step 8: Remove the upper part of the bumber, and the two screws fixing the IR beacon to the bumper.
Step 9: Lift off the top cover.
Step 10: Remove the centerplate.
Step 11: Remove the display/button assembly.
Step 12: Remove the five screws holding the main PCB.
The disassembly is now complete.
First thing was to measure that there was connection between the charging connection plates and the home base charge input on the main PCB.
Then I measured the connection between the rear and the front charging input. I found then that the ground signal from the home base charge input was routed to the centre pin of the rear charge connector. And that ground on the rear charge connector was connected to the pin to the left. I found this a little strange as the ground signal was expected to be the same.
Further looking at the external charge input connector, I did reckognize the type as one having an internal switch closing/opening when a plug in inserted. But inserting the charger plug did not make or break any connection. Just to verify my suspicion, that it was a missing connection between the two ground signals that was the problem, I placed a jumper between the centre and the left ground pin of the main board charge input connector, partly assembled the Roomba, and tested the home base towards the charge connection plates. And now everything worked as expected. Hence the problem was in the external charge input connector, not connecting the two ground signals when the external charger is not plugged. I guess the Roomba is designed this way in order to disconnect the home base charging input in case a external charger is connected while the Roomba is still in the home base charger.
Fixing the problem
As I had no suitable spare connector, I had to fix the original one. Using a drill and a dremel multi-tool I removed the plastic on one of the sides of the connector. And the by inspecting the internal switch I confirmed that this switch was left permanently open, even if the charge plug was not inserted. A little bending with a pair of pliers, and the functionality of the switch was restored. Removing the side of the connector had made the internal parts little loose, but this was nothing a little two-component epoxy glue could not fix.
Everything was reassembled and the Roomba home base now works perfectly.