What resistor ohm will work better to repair this waterpik?  - Page 1
Forum section: electronics / repair

author: artvandalai
author_rank: Regular Contributor
timestamp: January 05, 2025, 09:57:38 pm
content: The resistor on this waterpik blew. I changed it with the a similar spec 47ohm 2 watt yageo resistor but it still keeps blowing the resistor. Checking with the multimeter the motor, capacitor, diodes, and thermal fuse all checked normal. Will a higher ohm resistor work better? What ohm resistor will work better to repair this waterpik? This video is showing the repair with a 56 ohm resistor

author: fzabkar
author_rank: Super Contributor
timestamp: January 05, 2025, 11:29:27 pm
content: Was the original resistor a fusible safety type?https://www.digikey.com/en/product-highlight/y/yageo/fusible-through-hole-resistorsI suspect that there may be carbon dust between the commutator segments. Can the motor be disassembled?

author: Simmed
author_rank: Frequent Contributor
timestamp: January 05, 2025, 11:51:31 pm
content: use 2x 100Ror 3x 150Rspread the power

author: DavidAlfa
author_rank: Super Contributor
timestamp: January 06, 2025, 12:07:18 am
content: Maybe something is wrong in the mechanical part, overloading the motor?

author: fzabkar
author_rank: Super Contributor
timestamp: January 06, 2025, 08:02:20 am
content: Teardown:https://newscrewdriver.com/2022/07/11/waterpik-wp-150w-teardown/New motor (DF315XLG) for ~US$10:https://www.aliexpress.com/item/1005005779645234.htmlRating of Waterpik is 120V, 16.4W.Current draw is ...I = 16.4 W / 120 V = 0.137 ADissipation in resistor is ...P = I^2 x 47 ohms = 0.88W

author: Gyro
author_rank: Super Contributor
timestamp: January 06, 2025, 10:02:20 am
content: Quote from: fzabkar on January 05, 2025, 11:29:27 pmYes, it's a fusible type, as clarified in the OP's previous thread on this...https://www.eevblog.com/forum/beginners/what-type-of-resistor-material-and-tolerance-should-i-use/For it to keep failing, something must be overloading it (the motor). It's failing for a good (safety) reason.

author: artvandalai
author_rank: Regular Contributor
timestamp: January 06, 2025, 01:13:28 pm
content: https://www.digikey.com/en/products/detail/yageo/KNP200JB-73-47R/9119797I purchased these Yageo resistors. I didnt notice any black dust from worn motor brush. It was purchased new and only used a handful of times.

author: artvandalai
author_rank: Regular Contributor
timestamp: January 06, 2025, 01:30:48 pm
content: Im hoping its not the motor, the most expensive part to replace as this waterpik is for resale instead of throwing it out.

author: Gyro
author_rank: Super Contributor
timestamp: January 06, 2025, 09:31:00 pm
content: If it's had so little use, I would return it under warranty, something in the motor/pump/pipework sounds defective. Resale, with or without the correct safety resistor fitted, sounds like a headache in the making.

author: artvandalai
author_rank: Regular Contributor
timestamp: January 06, 2025, 09:38:07 pm
content: Thanks, its been two years since i bought this item. ive been holding it hoping to fix it. Wouldnt a higher ohm resistor as the video linked shows fix the problem from higher resistance from wear?

author: Gyro
author_rank: Super Contributor
timestamp: January 06, 2025, 10:15:51 pm
content: That's a shame.A higher value resistor will actually drop more voltage and so dissipate more heat if the motor is overloaded, so will fail quicker. What he's done in the video is to replace the 0.47R resistor with a much larger body non-fusible 0.56R resistor. Great for persuading the motor to spin again but throwing the overload protection of the original design out of the window. Using a slightly lower value fusible resistor would work if the design is marginal, but it really should work as designed, including staying safe.

author: fzabkar
author_rank: Super Contributor
timestamp: January 06, 2025, 10:33:15 pm
content: If you remove the motor, does the shaft rotate freely? Can you turn the geared mechanism freely?

author: cruff
author_rank: Regular Contributor
timestamp: January 09, 2025, 02:34:51 am
content: Is there also discoloration on the trace leading from the + terminal of the capacitor, or is that a lighting issue. Have you checked to see if that cap has a problem?