Resistor help please  - Page 1
Forum section: electronics / beginners

author: Jateu01
author_rank: Newbie
timestamp: January 07, 2021, 08:41:42 pm
content: Hi allI have a carpet cleaner that has just packed in. I have tested everything and the only issue I have is the resistor on what looks like a soft starter board. I have checked bands and I think it's 290ohms red white black black red but when I test it it comes out and 1M ohms. I have checked continuity and I don't get a beep. Please see pictures attached.Many thanks

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: January 07, 2021, 08:47:06 pm
content: 1M would be brown-black-green-gold which your photo could easily be.

author: Gyro
author_rank: Super Contributor
timestamp: January 07, 2021, 08:48:27 pm
content: Welcome to the forum,That looks as if it's just a discharge resistor to drain any remaining charge off the filter capacitor. It's there to prevent you getting a shock off the mains plug pins. 1M is about right in that case.I'd be looking for cable damage, mains switch and motor brushes / connections.

author: Jateu01
author_rank: Newbie
timestamp: January 07, 2021, 09:12:08 pm
content: Thank you guys.All components on filter board are good then. Checked incoming AC voltage and it was somewhat odd. Started at 2-5v then ramped upto 240v AC at the board. So I can assume incoming power cable is fine. The on off latching switch is fine and showing good continuity. The brushes on the motor are fine and making good contact. So it must be an issue with the crap connector rats nest.Thank you again.James

author: Jateu01
author_rank: Newbie
timestamp: January 07, 2021, 11:26:40 pm
content: I have continuity checked every connection and the attached image the the fault inside motor. Can anyone give me an idea of how to repair this.Many thanks

author: TimNJ
author_rank: Super Contributor
timestamp: January 07, 2021, 11:45:36 pm
content: Is the attached component open circuit? If so, then you’re looking at a thermal fuse, or thermal cut-off/cut-out (TCO).Usually, if it’s blown, it signifies there was either one severe overload (high temperature) condition, or many smaller instances of the motor operating at a temperature close to the Tf value of the TCO.You can replace it and see what happens but maybe double check that nothing else looks (or smells) like it melted.Common brands are SEFUSE, Therm-O-Disc and a few others. That one sort of looks like Therm-O-Disc G7 but I could be wrong.

author: Jateu01
author_rank: Newbie
timestamp: January 08, 2021, 12:07:15 am
content: Thank you TimNJ.The motor looks fine not burnt smell or loss of enamel coating from wires or and short circuits with either motor winding. The carpet cleaner was seriously blokes with animal hair etc so I assume the motor was under serious load all the other components are find and no melted wired or wire coverings. It's there a specific temp I should look at?Many thanks.James

author: bob91343
author_rank: Super Contributor
timestamp: January 08, 2021, 12:13:33 am
content: There is a clue here. If you checked the input voltage and it started slowly and gradually rose to rated voltage that is a sign of a corroded connection to the line. Check continuity and perhaps reflow solder connections and recrimp crimped ones and reseat connectors.

author: Jateu01
author_rank: Newbie
timestamp: January 08, 2021, 12:17:01 am
content: TimNJ I can just make out microtemp on fuse with a partial code of G4A I think. To therm-o-disc is spot on thank you.Bob I have checked all connections again and it was clearly me not holding still long enough all connections are perfectI believe the issue to be the thermal fuse in motor.Many thanksJames

author: TimNJ
author_rank: Super Contributor
timestamp: January 08, 2021, 12:24:06 am
content: Do you see any other number on there like 121, 128 , 134, 141?From memory, Therm-O-Disc color codes the fuses. I think brown is 128C. This kind of makes sense since the enamel coating on motor wires are typically rated for either 130C (Class B insulation) or 155C (Class F insulation).So 128C is a good choice to make sure the fuse blows (hopefully) before the enamel starts melting.

author: TimNJ
author_rank: Super Contributor
timestamp: January 08, 2021, 12:28:06 am
content: The hardest part will probably be doing a good job crimping a new one on:Check the end of this document for recommended procedures.https://climate.emerson.com/documents/microtemp-product-catalog-en-us-5125016.pdf

author: Jateu01
author_rank: Newbie
timestamp: January 08, 2021, 12:31:30 am
content: TimNJ. Crimping will be fine. The best I can do for temp is a partial as the ink is smudged. It looks like 23c or 28c so I would assume 128c is correct.