Author Topic: Resistor that looks like a capacitor  (Read 687 times)

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Offline zz28zz

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Resistor that looks like a capacitor
« on: November 28, 2019, 12:33:20 am »
Found a couple of capacitors on an old car stereo amplifier that measure as open and need to be replaced. They look like 1/8 watt resistors and have bands like a resistor.

They have the following sequence of color bands:
Brown-Green-Black-Gold-Black

I'm pretty sure that means 15p 5% but not sure abt the last black band.

Found a couple of color band maps online. The last band has to do with voltage but seems to depend what type of cap it is. Ceramic is not listed as an option. Can I assume 100V?

 
« Last Edit: November 28, 2019, 01:43:41 am by zz28zz »
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Offline floobydust

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Re: Resistor that looks like a capacitor
« Reply #1 on: November 28, 2019, 12:41:19 am »
can you post pics?
 

Offline zz28zz

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Re: Resistor that looks like a capacitor
« Reply #2 on: November 28, 2019, 02:05:41 am »
Here's a pic of one.  Cap is pretty small. DIP included for scale.
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Offline coppercone2

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Re: Resistor that looks like a capacitor
« Reply #3 on: November 28, 2019, 02:15:10 am »
I think they are called bumble bee capacitors
 

Online andy3055

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Re: Resistor that looks like a capacitor
« Reply #4 on: November 28, 2019, 02:21:44 am »
Since it is from a car radio/amp. you will be safe to use anything with 50v rating which is easily found.
 

Offline zz28zz

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Re: Resistor that looks like a capacitor
« Reply #5 on: November 28, 2019, 03:12:26 am »
Digikey has two 100V options but no 50V in stock. Guess I'll be going with a 100V.
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Online andy3055

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Offline zz28zz

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Re: Resistor that looks like a capacitor
« Reply #7 on: November 28, 2019, 06:47:55 am »
Is there any advantage to using a 50V as opposed to a 100V?

One of the 100V caps was low ESL. Any advantage to using low ESL caps at audio frequencies?
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Online andy3055

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Re: Resistor that looks like a capacitor
« Reply #8 on: November 28, 2019, 06:58:37 pm »
Is there any advantage to using a 50V as opposed to a 100V?

One of the 100V caps was low ESL. Any advantage to using low ESL caps at audio frequencies?

50v/100v is the working voltage. The higher the safer, but you don't need it to be so much in a low voltage circuit like this and the higher rated might be too large physically. As for ESL, I am not sure how the effect will be. I usually prefer caps that have low to no leakage.
 

Offline m3vuv

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Re: Resistor that looks like a capacitor
« Reply #9 on: November 29, 2019, 09:24:11 am »
that looks more like a choke to me?
 

Offline gbaddeley

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Re: Resistor that looks like a capacitor
« Reply #10 on: November 29, 2019, 09:58:09 am »
Yeah, me too. OP, where is it located in the circuit? Does it join two voltage rails, or is across rail to 0 V?
Glenn
 

Offline coromonadalix

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Re: Resistor that looks like a capacitor
« Reply #11 on: November 29, 2019, 11:22:21 am »
I would have said the same thing,  they are inductors  not resistors.

Show us photos where they go on the pcb ??  pcb markings ...
 

Offline zz28zz

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Re: Resistor that looks like a capacitor
« Reply #12 on: November 29, 2019, 07:31:38 pm »
Components in question are C559 and C560. I made rectangular outlines around them on the enclosed schematic. (The circled components were the ones I found to be overheated when I first started repair) 

The cap is sorta across the +/- 50V rails but not directly. See attached.

I'm not 100% sure they are open. Their advertised capacitance is below the lower limit of my cap meter. If I connect the two 15P caps in parallel then attach cap meter, it still reads open but I'm still right at the lower threshold of my cap meter.
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