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Bought a PCB with a dead Hbridge.
Sierra IC Inc
I’ve tested so far DSCF. You do not have the required permissions to view the files attached to this post. Using continuity, this is how far I got. Last edited by LazyRoomba on February 19,9: It would appear that you are now in need of a replacement PCA. Missing ground plane points will prevent the H-bridge from working correctly.
Replaced U11, with no difference. With both IC’s replaced with no difference, it could rule out IC failure, which is a good thing. I have a feeling Q65, Q69 and Q78 maybe the reason why the robot will only go backwards seems like no power when going forwards. Read through this thread for more clues: I’m wondering, just checked the data sheets for the diode used on the Right wheel, it’s a 1N, a shotkey diode.
74HC Datasheet, PDF – Alldatasheet
I’m wondering, do I have a damaged one? Sine the wheel in reverse, is litterally giving off the noise of an over revved engine kick back from top RPM as well as the bottom LED in BiT flashing.
Wheel has full current in reverse. I’ve checked all components in the right wheel of the H bridge that are known, and replaced over 15 components and the wheel will not move forward.
What ever the fault is, I don’t think it’s the H-bridge. Probably looking at the MCU itself.
I’ve also noticed, in BiT, the wheel moves backwards, and jamming creates alot of force, and I mean alot. It seems to be bypassing the current limiting chipset. All safety checks are inhibited during the BiTs so overcurrent would not stop the test.
Unless anyone has any ideas, I think I might just play around with it, watch it drive around datasheeet circles, keep my battery topped up datasneet continues to find wtf is wrong.
Dam Irobot for not releasing schematics. I’m open to ideas. I’ve just replaced D12 and the 4 diodes unsupprising as these diodes soke up any spikes from the motor when switching or turned off next to the B’s and D’s with no difference.
You may still be 74hc40 with a soldering issue somewhere on the board. To delve deeper into the drive wheel operation with troubleshooting, it would be greatly enhanced if an oscilloscope were available as well as another working Roomba. If you are careful you don’t need to worry about the battery voltage. Just take your time. Here’s my setup DSCF That seemed to be short on Q76, D64 and Q60 killed what’s left of the board.
MCU now “reboot loops” with a popping on the speaker. Charging works and fully charges the battery, but 5 volts is all over the place when running on the battery. I got creative with a razor datasneet. Shame I couldn’t get the camera to focus.