Capacitor type identification

[kwiturbichen]

Hope this is the right forum for this. What type of capacitors are these little green glass caps in this NAD preamp. I don't need to replace any, just never seen anything like them.

Thanks!

Having trouble with photos

 

[jaymanaa]

Here's what they look like.

 

[kwiturbichen]

Here's what they look like.

Thanks Jay. That was an odd problem.

 

[Leestereo]

Those are small value film caps for the low pass filter at the inputs. In my NAD 106 preamp they are 100pF polystyrene types with a green plastic (not glass) encapsulation.

 

[jaymanaa]

Cool, I've always heard good stuff about styrene caps. Can you elaborate on the purpose of the low pass filter.

 

[kwiturbichen]

Those are small value film caps for the low pass filter at the inputs. In my NAD 106 preamp they are 100pF polystyrene types with a green plastic (not glass) encapsulation.

Thanks. I just thought they were there to block any interference that might be on the input signal as it entered the pre. In the service manual I have for the unit they are listed as 68pF on the schematic and 100pF in the parts list. Interesting. I'm a little bit new at this and I just honestly had not seen anything quite like them.

 

[Leestereo]

The low pass filter in this case is to eliminate any radio frequency noise from entering the signal path; the interconnects can act as antennas. At each input there is a series resistor and a capacitor that goes to ground. In the above pictures, the resistor is 1kohm and if the cap is 100pF, the cut-off frequency is 1.6MHz.