Docking station charger problem, roomba 4000 need advice

numan · Joined: 05 Mar 2008 Posts: 42

I have a docking station that has developed a problem it won’t charge up the battery. The power supply is good that connects to the charger, and will charge the battery just fine when it is connected directly to the Roomba, the charger have a constant 22 volts on the charger. The dock when checked with a volt meter also has the correct voltage, the IR works on the dock, the Roomba will dock itself. Both the power light can charge light comes on, and appears to be charging, however I am guessing that the voltage either drops off or it is not pulling enough current to charge the battery. I took the dock apart, and checked the solder connections for the positive and negative leads and they are soldered very well, I could not see anything inside the dock that looks like it has been hot or any burnt smell. I also hooked the dock to another charger and the problem followed the dock so I know the problem is within the dock. I also checked the contacts very well, and cleaned them contact cleaner and had the same results.

I was wondering if there is a component or components, that I can check or is there a common failure inside the dock I could look for. If I can fix it I would really like too, I hate to toss something out if there is a chance of it begin repaired, by a couple of dollars of parts, with just a little time and effort. :?:

Thank you,

Fraggboy · Posted: May 9, 2008, 3:56 am Post subject:

Numan, I think your issue might be in the Roomba. You stated that your dock checks out good, even with a different charger. The voltages look good, and like you said that when you plug directly into the Roomba, it charges. So, I am thinking that there is something wrong with the Roomba itself. I'm sure Gordon, Vic or someone else who has knowledge in that area can help you troubleshoot..

Just my $0.02

numan · Joined: 05 Mar 2008 Posts: 42

Sorry I guess I did not explain correctly, the roomba charges just fine with the charger, and with another docking station. If I put the problem docking station with any of my other Roomba I get the same results, the dock itself will not charge a battery. It acts like it is working and the Roomba flashes like it is charging but it is not charging. Sorry if I did not explain the problem correctly.

Fraggboy, thanks so much for your reply.

Fraggboy · Posted: May 9, 2008, 5:28 am Post subject:

Gotcha!! ;) Give the experts a little bit to chime in and help you troubleshoot your dock. I am totally clueless in that arena..

At least you pinpointed where the issue is..

vic7767 · Joined: 14 Jan 2006 Posts: 3099 Location: Louisiana

You might check this post and see if there is info in it to help you.

http://www.roombareview.com/chat/viewtopic.php?p=13478#13478

Gordon · Posted: May 9, 2008, 12:20 pm Post subject:

vic7767 wrote: You might check this post and see if there is info in it to help you.

http://www.roombareview.com/chat/viewtopic.php?p=13478#13478 That's a great link, vic7767! One of the most important posts is of Rodbot's observation, and subsequent correction of U2's gate-drive. He said something like this: Rodbot approx wrote: The fault was in the base, the value of R10 was a wrong 180K instead of an expected 20K or so. The wrong value kept the N3PF06-mosfet's gate-to-source voltage at a high 20V (the max permitted value) so a small overvoltage could destroy the gate's thin insulation layer. By changing R10's value to 22K ohms, the gate-ON voltage is 11V. In addition to replacing U2, if the installed R10 has a 180k value, reducing it, as prescribed, would seem appropriate.

numan · Joined: 05 Mar 2008 Posts: 42

I have not had the time yet to see if I can repair the docking station, but as always thanks for the help in the link to the old thread, going to see if I can figure it out and I will post back.

Thanks, everyone