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The Oral-B Triumph v2 is an electric toothbrush series. Models include the Oral-B Black 7000 (depicted and used in the guide) as well as brushes with types 3761, 3762, and 3764.

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Runs down and stops in about a second

My toothbrush runs down and stops in about a second. I fixed the problem a few months ago by unsoldering and then resoldering the battery. I have checked the battery voltage during the switch on, slow down and stop phase and it remains constant at about 3.7V so there would seem not to be a problem with the battery. When the problem occurred before I found that bypassing the MOSFET caused the motor to run normally at full speed, so this seems to be a microprocessor issue. I have tried resetting the brush by holding the power button for ten seconds. There is no water inside.

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Fixed - there is a polyfuse marked PP which is Bourns MF-PSML300 rated 3A and it was dropping several volts. Bypassed fuse with multimeter on current setting, toothbrush works and meter reads 0.5A so fuse clearly faulty. Bridged fuse with solder for permanent fix. It is possible to buy replacement fuses but they are expensive and not easy to fit.

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bypassing a fuse is never a good idea for a long term solution. SMD parts are not simple, but this part is big so it should not be a big problem.

These are 0.18¢ each - min quantity 10.

https://www.aliexpress.com/item/22518327...

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I had the same problem with a similar OralB toothbrush. It would charge and start, but run down in 1-2 seconds. Battery seemed fine, but the polyfuse measured 3-4 Ohms. That's completely out of spec. So I replaced it with a tiny strand of wire. Works again as before.

Thanks for the pointer!

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That's a 1206 package, OEM is an 0805

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