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How alex replace capacitors without measuring thier values ??

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(@Mouadh)
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Joined: 2 years ago
Posts: 1
Topic starter  

I had 2 missing caps in my board , 22uf and 47pf , if i put any caps about yhe same size and color  no matter the value of them will it works ??


   
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(@abrsvcs)
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Joined: 2 years ago
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There are a few things to consider:

1) Replacing caps using a donor board where the locations are the same means that you don't need to know the value.  A 1-to-1 replacement will work.

2) You can measure the part from another working board to determine the value and replace based upon that.

3) Having repaired a number of similar units, you might know what the value actually is.

Note too that in many cases, the caps that fail are filter caps that provide power to ICs.  These caps values are not critical.  In this mode a 10uf cap vs a 22uf cap will function just fine.  Critical cap values would be in different circuit positions and are less likely to fail.  Careful watching of many of these videos will show that the caps that fail are almost always on the power rails.

Hope this helps,

Dan


   
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(@Guest 10344)
Eminent Member Guest
Joined: 2 years ago
Posts: 21
 

The rule of thumb is that capacitors in the same magnitude should work. So if you replace a 22uf cap with 50uf cap it should work. But they have to have the same or higher voltage rating. Replacing a cap rated for 10V  with a cap rated for 3 volts is not advisable at all.

Again this rule of thumb does not apply in audio circuits. Audio circuits are very sensitive and the filter they use have to have the same exact values.


   
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(@Guest 10257)
Active Member Guest
Joined: 2 years ago
Posts: 17
 

As others have stated, so long as you meet or exceed the capacitance value in Farads and voltage rating you should be good to go for power applications. Ensure you mind polarity for electrolytics though! Matching ESR can be a secondary concern but not as critical. Audio or RF applications the circuit is tuned to a specific value to create the desired impedance for a given freq but DC doesn't care lol. Any more in depth discussion is probably beyond the scope of your question but you can go pretty far down the rabbit hole if you're interested.

Hope this helps!

Dan,
Second Chance Repairs


   
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