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| ESR Value for Electrolytic Capacitor question |
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| AndyA:
I'm fixing a SMPS supply from my sound bar. I have discharged all the caps safely. If I measure the ESR with my DER EE-5000 on a Sam Young NHA 1000uF 35V I get 0.03. I can't find the ESR for any of the Sam Young caps online. So far as I can tell this one is OK. When I measure 2 of the Sam Young NHA 470uF 10V I get an ESR of 3.7 and 4.2. Is this within spec or are they bad? Can I test the ESR of a capacitor in circuit when in parallel or series and still get the correct reading? Thanks |
| Shock:
--- Quote from: AndyA on December 02, 2018, 11:35:09 am ---Can I test the ESR of a capacitor in circuit when in parallel or series and still get the correct reading? --- End quote --- If you check on google images for ESR charts it will tell you even 10/20 years ago whenever those charts were made ESR for a 470uF 10V should be around 0.2 ohm or less, so yes that reading is quite high. If there are other capacitors or resistances in parallel it can throw off the reading, remove them from circuit and double check. Check capacitance as well. If the electrolytic capacitor has brown gunk leaking out, a raised or domed top, a blown bung or any discoloration below it on the PCB it's venting and needs to be replaced. For SMD caps sometimes you will see faded printing which points to leaking electrolyte. |
| wraper:
--- Quote from: AndyA on December 02, 2018, 11:35:09 am ---When I measure 2 of the Sam Young NHA 470uF 10V I get an ESR of 3.7 and 4.2. Is this within spec or are they bad? --- End quote --- Certainly bad. BTW you should measure ESR at 100kHz, just in case. |
| kripton2035:
+1 for bad caps. first to try to sap with a good one. how old is the soundbar ? |
| AndyA:
Do you mean 100Hz or 100kHz? The sound bar is at least 8 years old. |
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