Components identification

[Robyn]

Hey everyone,

I've just pulled apart an old hifi to scavenge some interesting components. Score! I got some free voltage regulators, a nice power supply etc.

I've got a couple of questions though, I found some nice looking resistors and caps that I'm not sure what they are. I guess the resistors are some sort of heavy duty ones and maybe the caps are tantalum. What do you guys think?

Also, I've unsoldered the main amp unit but some thermal paste got onto the pins (the white stuff). It's really hard to clean out and I wonder if that will be an issue, eg. the paste is conductive and will short the pins.

Thanks for your time!

 

[Harald Kapp]

The resistor is 0.22Ohm, 2W, probably a current sense resistor.
The capacitor is not tantalum, it is a polystyrene film capacitor.

Thermal grease is normally non-conducting. Use an Ohmmeter to find out.

 

[Robyn]

Thank you Harald!

I am very happy about those polystyrene caps, they are the reason why I pulled that thing apart in the first place. I just got used to see polystyrene film caps in boxes and tantalum in silver casings so I got it wrong... How did you identify it?

I had never heard about a current sensing resistor. I looked up the definition and I understand that they create a voltage drop proportional to the current flowing through. Isn't that what all resistors do though???

 

[Six_Shooter]

Yes, all resistors cause a voltage drop, but in this case the voltage drop is read across that resistor and used by another device to determine the current flowing through that resistor and attached circuit.

A low value is used to have a low, but predictable voltage drop feeding the circuit.

 

[Robyn]

OK so it is not the resistor that is current sensing but the way you use it right?

 

[Harald Kapp]

Right.