Hi, I have a pair of salvaged Polystyrene capacitors that I plan to reuse in an amplifier I'm building but am just wondering if anyone can help identify the outer foil terminal on them.
I've looked online but can't find any information on these particular models, they're both 470pF and have "YX" printed on them in hard to read print. Both of them appear to have some faint yellow coloring at one end which could indicate something, but like I said its very faint.
I tried the oscilloscope trick and pinching it with my fingers but the amplitude of the hum pickup was about the same, I also fired up my old LM386 amp and cranked the gain right up but didn't really notice a difference in hum loudness. I guess its because the cap is so small that there isn't enough surface are for the method to do its thing.
Any pointers in finding out the foil end would be great! 🙂
I've looked online but can't find any information on these particular models, they're both 470pF and have "YX" printed on them in hard to read print. Both of them appear to have some faint yellow coloring at one end which could indicate something, but like I said its very faint.
I tried the oscilloscope trick and pinching it with my fingers but the amplitude of the hum pickup was about the same, I also fired up my old LM386 amp and cranked the gain right up but didn't really notice a difference in hum loudness. I guess its because the cap is so small that there isn't enough surface are for the method to do its thing.
Any pointers in finding out the foil end would be great! 🙂
Attachments
Last edited:
Isn't is so simple that the leg that dosen't seem to come out from the middle of the roll comes from the outer foil. Not that it matters but anyway...
//
//
To be fair both legs are coming out around the same spot on the roll (I did check before posting). Also I read that it can matter as the outer foil end can act as an antenna if connected to a high impedance node, most people recommended connecting it to a more "ridged" potential in the circuit such as ground in my case of RC filter.
Last edited:
Probe it with a sharp pin and a continuity tester. Or connect one leg to the microphone input of your PC, and move your finger close to it. Then swap the legs to the input. Where you hear bigger hum is the leg connected to the outer foil.
Update: I was able to conduct a conclusive test using my oscilloscope, the difference in noise pickup was only slight (100mV) but using the AC RMS voltage readout I could see side was which (yellow tinted end was in fact the foil side).
that's good.
If you have a sensitive capacitance meter. Wrap the capacitor in metal foil. Measure the capacitance of each leg to the foil. The one with the higher capacitance is the outer one.
- Status
- Not open for further replies.