I just opened up an old piece of electronics. While salvaging, I found a board with this waxy stuff on it? What is this and what is its use?

A Picture of the Board

P.S. The substance I am talking about is the lightly tanned wax on the top right of the board.

  • 1
    \$\begingroup\$ Out of curiosity: What is that device you're salvaging from? \$\endgroup\$ Commented Jul 14, 2017 at 17:28
  • \$\begingroup\$ Please be explicit as to which substance you mean. There are at least two substances in the image which I can interpret your question as referring to. I would suggest using a hand dawn red circle in the image to explicitly indicate what you are talking about. Presumably you mean the light tan colored substance in the upper-right of the enclosure. That is the substance which is discussed in your highest voted answer. I think the other non-negative answer is talking about the blue substance in the tune-able coil in the bottom center of the PCB. \$\endgroup\$
    – Makyen
    Commented Jul 15, 2017 at 2:34
  • \$\begingroup\$ it is from an old TV sharpness controller. \$\endgroup\$ Commented Jul 15, 2017 at 6:59
  • \$\begingroup\$ Not just old stuff. See electronics.stackexchange.com/questions/191024/… \$\endgroup\$
    – Paul Uszak
    Commented Jul 15, 2017 at 12:26

2 Answers 2


Am guessing that the wax-covered part of the circuit is a radio-frequency oscillator. The coil of wire has been hand-tuned by spreading its turns so that the oscillator frequency matches up with other (transmitting? receiving?) equipment. The wax stabilizes this coil so that it doesn't shift frequency.
Disturbing the wax can de-tune the oscillator.

  • 7
    \$\begingroup\$ The wax also excludes moisture, which could also affect the tuning. \$\endgroup\$
    – amI
    Commented Jul 14, 2017 at 16:33

It's wax. It was applied on the assembly line in order to 'nail down' an iron ferrous core in an inductor coil in some highly critical valued circuit I wager.


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