Electronics > Beginners

White material at base of capacitors

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fixit7:
These boards are from a junked Yamaha receiver I found.

What is the white material at the base of the capacitors?

I noticed it resists efforts to desolder it.

https://www.dropbox.com/s/gjg2nscusaum0mn/CapsWithWhiteMaterial.jpg?dl=0

I see copper coils around some resistors while some are free standing like the ones next to the relays.

I thought maybe the coils are some kind of shielding?

https://www.dropbox.com/s/x1jh6hhnfdqesp1/AudioBoard.jpg?dl=0

blackbrayn:
The white stuff it's glue , to hold down large components on the board so the solder joints will not get afected by things like shocks , general vibrations.
As time pased a lot of glue types were used for the job , in recent yeas the white type it's the most common one.
I'm sure it has a specific name , some forum member with more experience will know.

blackbrayn:
The coil and resistor construction is common in audio amplifers , you will see it in schematics on the output stage of the amps.
Quick example i found on google : "R19" and "L" in the picture.

mariush:
Like another person said above, the white stuff is just a somewhat elastic material put there to prevent vibrations, solder cracking on the other side and so on ... it holds the big capacitors in place.

As for resistor inside the coils ... my guess is simply because there is space within the coil for the resistor,  I don't think it's any special reason.

fixit7:

--- Quote from: blackbrayn on May 29, 2019, 09:42:36 pm ---The coil and resistor construction is common in audio amplifers , you will see it in schematics on the output stage of the amps.
Quick example i found on google : "R19" and "L" in the picture.

--- End quote ---

Thanks.

The radio is 240 watts.

I think the clicking I hear when turning on another radio (Denon) comes from a relay.

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