Yes you did!ifcho wrote:Hello, Today I took my Roomba 630 from the post office and I ... immediately killed it.
That is typical for inexpensive wall-wart power adapters that lack any type (voltage or current) regulation. The first Roombas (2XXX & 3XXX) were built to use a like power adapter having 24Vdc output when delivering 0.5A current. With current = zero, the output voltage was about 28 volts. Years ago I experimented with that 24V,0.5A unit by powering it with a variable voltage transformer, and with its dc-volts output fed straight to a Roomba battery (12S cells as in your 6XX battery) through an ammeter with 20A full scale range. As I ramped up AC voltage, heading to 120VAC, I witnessed current quickly exceed the adapter's 0.5A operating point; and upon raising input voltage even higher, yet far below the 120VAC goal, I saw output current climb up to several amperes (and quickly reduced the AC power)!...The generic charger I took, is 24v/1A output, but apparently, when I measured it with a multimeter it gives out 50V without load :-/
That can be explained for charging mode if fuse F2 tripped open, resulting in de-powering the Roomba controller. And the likely thing to make that happen is for Roomba to have actually entered charging mode, which would have been assisted by two TVS diodes (acting in //) to load the troublesome adapter's output down to some level around 30V. Then, IF charging became authorized by the controller (thus switching into conduction the two charging FETs, a very high charging current would have flowed through Fuse F2. Current would have been on the order of: I_chrg ~ (30 - 15.8) / 0.1 = "142" amps! Nah, we know that can't happen, instead we have to presume a high enough charging current momentarily settles in to pull adapter-output down closer to battery voltage (plus the voltage drop across the battery's ESR -- which voltage drop I assigned as 0.5V (that was added above to the 15.3V battery level))....while the Roomba was on the home base both lights (home base and roomba) were blinking , along with a warning sign. I think my next action killed the roomba, as I moved the charger directly to it, it was still blinking with the warning sign on its display. After a while it just turned off all its lights.
Three things here:I removed the battery a couple times (it gives out 15.3V), and tried to reset the robot, but still nothing.
Well, I have already done that above, to an introductory level. However, it is important for you to know that I have never touched a model 6XX Roomba, therefore anything I say about the 6XX circuitry is based on the assumption that 6XX circuits are identical to those in 5XX, "R3" Roombas. I have read about that consistency ( 6XX versus 5XX PCA) on this rr board.Do you have any guidelines or suggestions what could have happened?
Yes, generally changed for the better, and different enough that R2's schematic1 is of no value to your problem.I found a schematic sheet of the power board of an older Roomba model, but probably, much has changed since then.
Yes, iRobot continues to connect TVS devices with no means to protect the device from dc current (not that they are specified to snub dc power). TVS devices are carefully specified to absorb energy contained in a specific shape pulse-current vs. time curve.I see that blown up TVS circuits are common cause for such issues. Do the recent Roomba models still use this type of circuits, and do you know what would be the P/N for replacements?
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