Resistor size for capacitor

[DB8219]

I have a 26 year old woodworking single phase combination machine with three individual 2.4kw motors, It has two arcotronics 40uf capacitors to start up and run, one of which has failed.I can obtain a suitable capacitor replacement but it does not come with a resistor like the old one. The old resistor has a code yellow,violet,yellow and gold which I think is 470. My question is what is the correct power rating for the resistor 0.25w or 0.5w. Also the

replacement capacitor will have a plastic cap on the can instead of an aluminium cap will that make a difference? I have attached a photos

 

[Nigel Goodwin]

It's 470K (470,000 ohms) - I would suggest a 1W type, as higher wattages are usually rated for higher voltages.

It has no effect on operation, it's just to provide a discharge path for the capacitor.

 

[AnalogKid]

That body type looks like a metal film resistor. You can measure the end cap diameter with calipers, and compare that dimension to datasheets. Or, since the part is a pretty snug fit between the two Faston tabs, measure the distance between the tabs and compare that to datasheets.

Based on the distance between the tabs my screen image, my guess is that the original part is a 1/2 W type. This will dissipate 1/8 W at 240 Vac, a nice, conservative number.

ak

 

[DB8219]

Hi, Thank your reply .I have crudely measured the length of the resistor and in between the tabs and its around 9mm in length would that be the the size for 0.5w or should I use 1.0w

 

[Nigel Goodwin]

Hi, Thank your reply .I have crudely measured the length of the resistor and in between the tabs and its around 9mm in length would that be the the size for 0.5w or should I use 1.0w

As I mentioned above, generally the higher the wattage the higher the voltage - and a 1W resistor is less likely to fail. 470K is also a common value that fails in valve amplifiers, and replacing them with 1W stops them ever failing again.

If you already have a 0.5W one then by all means use it, but if you've got to go and buy one, then buy a 1W.

 

[DB8219]

Thank you Nigel, please excuse me if I ask the dumbest of questions.My last silly question is what solder do I use at the tabs /terminals it being high voltage?

 

[AnalogKid]

The voltage does not dictate a special solder. Use something intended for electronics (as opposed to plumbing or jewelry).

ak

 

[Nigel Goodwin]

The voltage does not dictate a special solder. Use something intended for electronics (as opposed to plumbing or jewelry).

ak

Exactly - I'd also advise leaded solder rather than unleaded, as unleaded is crap

 

[Shagreobe]

You dont HAVE to solder the resistor, If you have space on each of the terminals, you could use solderless spade terminals