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HELP! Capacitor identification needed

Thanks for looking at my post. I am clumsy and broke a capacitor off a circuit board in an encoder. This encoder is probably 30 years old. The capacitor is made, I think, by NEC, because it has marked +NEC at the bottom. The device has the following markings: 6.8-M

20VE

+NEC The letter "E" after the "20V" is twice as big as all the other letters and numbers. I have contacted NEC and they said they cannot help me, the device is too old. I think it might be a tantalum capacitor. The reason I think it's a capacitor is because the circuit board has printed on it "C1" and the symbol of two parallel, vertical lines with each line having a line perpendicular and bisecting the vertical line. These markings are right next to where the capacitor is soldered to the circuit board. This capacitor is soldered across the positive and negative where the 5 volt power comes in to the encoder. Thanks for any help. Eric R Snow, E T Precision Machine

Reply to
Eric R Snow
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This could be a 6.8 Microfarad 20 Volt tantalum cap if it is across a power supply connection as you have indicated. Fortunately this is a non-critical application and it may not even need a cap there depending on how much by-passing is done elsewhere in the circuit, assuming your description is correct. The purpose of the cap is probably to reduce noise on the 5 Volt line and has little to do with the operation of the encoder, per-se. Remove the cap and see if the circuit works without it. A new 6.8 uF 10V or more aluminum or tant electrolytic cap should work fine in that application if you feel it needs replacing or if there is any noise or erratic behavior without a cap. Be sure to observe the polarity of the cap when replacing it. Bob

Reply to
Bob Eldred

Thank You Bob, It seemed to me that the cap was there for some kind of filtering. I'm glad that my guess was probably correct. I'll try the thing without the cap to see what happens but I'm going to buy and install a new cap anyway. This encoder is used in a machine shop with other cnc machines nearby and a TIG welder in the same building. I don't know much about how noise is picked by wires but I can hear the servo amps on one machine through an AM radio. Cheers, Eric

Reply to
Eric R Snow

Then replace the cap before you try to run it - it helps filter out that noise so that your encoder will operate reliably.

Cheers! Rich

Reply to
Rich Grise

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