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short circuit where capacitor sat ?
short circuit where capacitor sat ?
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Old 4th October 2018, 05:18 PM   #1
zoazim is offline zoazim
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Question short circuit where capacitor sat ?

Hi

I am trying to fix and change the capacitor on my defective internal powersupply to a Behringer UB1832FX-pro mixer.

After unsolder/removing the capacitor, I then measure the emtpy boards "sockets" +/- with a beep-connection-test, and the multimeter actually beeps, as there is a connection(!) where Capacitor should sit, with no capacitor there(!)

Is this ever normal? If not, how can this be / how can I fix it?


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Old 4th October 2018, 05:27 PM   #2
Mooly is offline Mooly  United Kingdom
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short circuit where capacitor sat ?
A short circuit would read a theoretical 0.00 on the meter or in practice the same as you see when you short the meter leads together.

Seeing an 'unknown' reading as you show is perfectly normal. It doesn't mean there isn't another issue somewhere, but you will always read something measuring across parts or their locations on a populated PCB.
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Old 4th October 2018, 05:33 PM   #3
zoazim is offline zoazim
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Ah, thanks

But when I solder on the 1000uF Cap, the reading is still the same.
All other Caps show a 1 in the multimeter

Is this normal too?
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Old 4th October 2018, 05:47 PM   #4
Mooly is offline Mooly  United Kingdom
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short circuit where capacitor sat ?
When you have the meter on 'Diode Test' (as your picture shows) it is actually displaying the voltage between the test leads, not resistance.

If you test a silicon diode or transistor out of circuit you should see somewhere around 0.650 meaning 0.65 volts (the forward volt drop across the device). Turn the leads around and you see whatever the meter displays when the leads are open circuit.

So using the diode range to interpret resistance won't work although a dead short is always going to close to 0.00 on the display.

Use the '200' range for checking for low resistances and short circuits, but even here the readings can be affected by other components interacting with the one you are measuring.
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Old 6th October 2018, 12:14 PM   #5
Vovk Z is offline Vovk Z  Ukraine
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short circuit where capacitor sat ?
1. There is pre-load resistor (0.25-0.5-1.0 W) somewere at the output. So it may by normal.
2. Cap, near the unsoldered (on the left) - not good too (usually they die together if they are connected in parallel). So, you have to change them all.

Last edited by Vovk Z; 6th October 2018 at 12:18 PM.
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