Resistor replacement

Thread Starter

spike1947

Joined Feb 4, 2016
167

Hi
I have a board that has 2x R220 and 1xR56 , 220ohms and 56Ohms respectively' resistors on it, I think they are rated at 1/2W , now I can only get 3W from this supplier along with other stuff, will that be ok ? .


cheers


Spike
 

dl324

Joined Mar 30, 2015
11,231
If they'll fit. You can determine wattage from the size. The only complication is that manufacturers make some "small" package resistors that dissipate twice the power of the traditional sizes.
 

Thread Starter

spike1947

Joined Feb 4, 2016
167
If they'll fit. You can determine wattage from the size. The only complication is that manufacturers make some "small" package resistors that dissipate twice the power of the traditional sizes.
Hi
Thanks for your reply, yes I know the general size vs W , I just wanted to know if there would be a problem to fit a 3w resistor in place of a 1/2w !
Spike
 

jpanhalt

Joined Jan 18, 2008
10,068
What is the construction of the current resistors? Carbon, metal film etc. Same question for the 3W. Many higher wattage resistors (about half on Digikey) are wire wound, and depending on use, that inductance could be a factor to consider.

Do you mean 56 Ω or 560 Ω?

As for space, very definitely an issue to consider. If through hole, you can turn the bigger resistor vertically and mount like that. Like this:
1595789231087.png
 

Thread Starter

spike1947

Joined Feb 4, 2016
167
What is the construction of the current resistors? Carbon, metal film etc. Same question for the 3W. Many higher wattage resistors (about half on Digikey) are wire wound, and depending on use, that inductance could be a factor to consider.

Do you mean 56 Ω or 560 Ω?
Yes the wording was a bit confused R56 =56 ohms= Fifty Six .
 

jpanhalt

Joined Jan 18, 2008
10,068
Then use carbon.

BTW: Units that are the names of people are not capitalized when referring to the unit and used in a sentence; whereas, the label for the unit (e.g., W) is always capitalized. Poor George Ohm is denied the capital "O" as the unit for resistance, unfortunately.
 

jpanhalt

Joined Jan 18, 2008
10,068
Why do you think the resistors are bad? Unless burned by over current, they are usually quite reliable.

The picture you show looks like the wire is melted, but the resister looks fine. What happened?
 
Last edited:

WBahn

Joined Mar 31, 2012
26,047

Hi
I have a board that has 2x R220 and 1xR56 , 220ohms and 56Ohms respectively' resistors on it, I think they are rated at 1/2W , now I can only get 3W from this supplier along with other stuff, will that be ok ? .
The 56 Ω resistor you show in the picture doesn't look like 1/2 W, more probably 1/4 W, but perhaps the picture is misleading as to scale.

In general, using a higher-wattage resistor OF THE SAME KIND is not a problem provided it can physically fit in the space provided; certainly there are exceptions, but it is unlikely that a 5% tolerance resistor would be used in most such situations. For use in the application you are talking about, it is doubtful that even using a different kind of resistor would cause an issue (but we can't be sure unless we see the schematic and even then it might not be clear).

Why can't you just use another supplier? I would expect that 3 W resistors might be sufficiently more expensive that it might be worth going elsewhere. But depending on where you are located, that might not be the case or even an option.
 

Thread Starter

spike1947

Joined Feb 4, 2016
167
The 56 Ω resistor you show in the picture doesn't look like 1/2 W, more probably 1/4 W, but perhaps the picture is misleading as to scale.

In general, using a higher-wattage resistor OF THE SAME KIND is not a problem provided it can physically fit in the space provided; certainly there are exceptions, but it is unlikely that a 5% tolerance resistor would be used in most such situations. For use in the application you are talking about, it is doubtful that even using a different kind of resistor would cause an issue (but we can't be sure unless we see the schematic and even then it might not be clear).

Why can't you just use another supplier? I would expect that 3 W resistors might be sufficiently more expensive that it might be worth going elsewhere. But depending on where you are located, that might not be the case or even an option.
Hi
Yes I think they could be 1/4W , they measure about 8.5mm length and 2.74mm thickness
 

Reloadron

Joined Jan 15, 2015
5,604
Take this for what it's worth or not worth. Resistors just don't fail and when we see a cooked resistor what we see is generally just a symptom and not a cause. The question then begs why did a resistor have excessive current causing it to fail? Then we can add if I replace a 1/2 Watt resistor with a 3 Watt what will happen to whatever caused the initial failure? There is a very good possibility that you replace the cooked resistors and promptly have more cooked resistors.

Ron
 
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