H-Bridge mini mod

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H-Bridge mini mod

Postby vic7767 » November 20th, 2012, 5:18 pm

Although no-one has actually experienced a true hardware failure of the H-Bridge NPN/PNP bi-polar transistors used for the drive wheels on the 500, 600, and 700 Roombas, a little preventative mini mod can be done to improve the odds of never having the issue. Using a pair of cutters, one can form a set of heat sinks from something like a blank aluminum name plate. Just cut it into quarters then apply a dab of thermally conductive silicone adhesive and mount each strip to the back side of each transistor. The adhesive sets up hard in 24 hours.
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Re: H-Bridge mini mod

Postby Gordon » November 23rd, 2012, 1:24 pm

Just a little side note, vic. As of the very next day (21st) we can no longer make this claim:
vic7767 wrote:Although no-one has actually experienced a true hardware failure of the H-Bridge NPN/PNP bi-polar transistors used for the drive wheels on the 500, 600, and 700 Roombas, ...
Member matofill reported in this post replacing two power xstrs in his R3-Roomba that effected operational repair. Communication with matofill brought forth data that strongly suggests his transistors failed due to some cause other than over-heating.
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Re: H-Bridge mini mod

Postby TechGuy » November 23rd, 2012, 2:40 pm

The other cause may be water damage as the H-Bridges are not covered by the plastic under the keypad.

I had repaired a 540 with one of the wheel running all the time with transistors failed shorted.
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