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Looking for rheostat


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  • Looking for rheostat

    I am looking for volume, balance and tone rheostats for a Modular Component Systems, 3845 Stereo Integrated Amplifier, MCS Series, Model #683-3845-890, distributed by JCPenney, made in the late 1970's I believe. Someone recommended on a forum that I replace them if they are film type because the sound fades, is scratchy, cuts out, etc. Are they film type? I know nothing about electronics. Thanks.

  • #2
    three places to try are MOUSER electronics in texas, NEWARK in new jersey and ALLIED also in texas. balance controls are linear. volume controls are audio taper. volume can be film type as is the balance control. large power types are wirewound and measured in watts. film type are also measured in watts besides the ohmic resistance of the control.


    • #3
      I just posted a rather lengthy response to your first post with an illustration that may help you understand.

      The device that you are calling a rheostat is properly called a "carbon film potentiometer" or in the electronics trade it is more commonly called a "pot".

      Pots come in many different ratings and you must use the correct pot.

      If you look on the metal can that covers the rotary section of the pot you will see the rating embossed into the metal. Typically 5K, 10K, 50K or 100K ohms.

      I am attaching an illustration that may help you understand how a pot works.

      You will notice that the signal input is on the center connector and the two end outside connectors are attached to opposite ends of the carbon resistor strip.

      Imagine that the control shaft is rotated so that the movable wiper is all the way over at the left hand end of the resistance strip. If you were to then connect your output lead to the left connector the resistance would increase as you rotate the knob clockwise, whereas if you were to connect to the right side connector the resistance would decrease as you rotate the knob clockwise.