Radio crackles while turning volume knob- 1970 U79 stereo - NCRS Discussion Boards

Radio crackles while turning volume knob- 1970 U79 stereo

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  • Mark E.
    Extremely Frequent Poster
    • March 31, 1993
    • 4503

    Radio crackles while turning volume knob- 1970 U79 stereo

    Otherwise, AM and FM work fairly well (tone quality from the two dash speakers isn't much to brag about, but I suspect normal).

    The radio hasn't been used in many years. Should I try exercising the volume control to see if that helps?

    Or apply a radio tuner cleaner?

    Or is this a problem that's more involved and will just get worse?
    Mark Edmondson
    Dallas, Texas
    Texas Chapter

    1970 Coupe, Donnybrooke Green, Light Saddle LS5 M20 A31 C60 G81 N37 N40 UA6 U79
    1993 Coupe, 40th Anniversary, 6-speed, PEG 1, FX3, CD, Bronze Top
  • Stephen L.
    Extremely Frequent Poster
    • May 31, 1984
    • 3149

    #2
    Re: Radio crackles while turning volume knob- 1970 U79 stereo

    The problem appears to be some dirt in the volume potentiometer. I was able to correct the same problem on my C2 radio by carefully

    Comment

    • Mike E.
      Extremely Frequent Poster
      • February 28, 1975
      • 5136

      #3

      Comment

      • Alan D.
        Extremely Frequent Poster
        • December 31, 2004
        • 2031

        #4
        Re: Radio crackles while turning volume knob- 1970 U79 stereo

        Add some light oil to the pot (volume control)

        Comment

        • Leif A.
          Extremely Frequent Poster
          • August 31, 1997
          • 3614

          #5
          Re: Radio crackles while turning volume knob- 1970 U79 stereo

          Mike,
          Fairly common issue with these old cars. They sit too long without being "exercised"...especially, things like the radio. Mine had the same issues. I used the product listed below (DeoxIT D5...availabel from Radio Shack). Removed the control knob, shot some on the shaft and worked the shaft back and forth. The more you use the radio the less the problem will appear. If you don't use it often, this fix seems to last about 6 months before having to do again. But, a 15 minute job at the most. Good listening!!

          Leif
          '67 Coupe L79, M21, C60, N14, N40, J50, A31, U69, A01, QB1
          Top Flight 2017 Lone Star Regional

          Comment

          • Gary R.
            Extremely Frequent Poster
            • March 31, 1989
            • 1796

            #6
            Re: Radio crackles while turning volume knob- 1970 U79 stereo

            Hi Mark
            I have the same deal with my 72. I used Deoxit to spray down the pot shaft and it did help but I want to pull the radio when I get time and go through it.

            Here is a link to last year

            Comment

            • Ed S.
              Extremely Frequent Poster
              • August 6, 2014
              • 1377

              #7
              Re: Radio crackles while turning volume knob- 1970 U79 stereo

              Mark - DO NOT spray anything on to your volume control mechanism to clean it other than a product called DEOXIT.

              I had my original 64 radio repaired a few years ago by Jerry Rudbeck - probably the best C2 radio repair guy ever (he is retired now) In addition to giving me a detailed breakdown of what he did to it, he also send me a short note with recommendations to keep it operating in great shape.

              He told me that one issue that is common to mid 1960s GM radios is the design of the on/off & volume control. It contains a stack of small carbon disks that have a tendency to corrode - and get dirty - that is what causes the static when you turn the knob. If you use WD40 or similar products it permanently damages the disks. Jerry recommended using a spray product called DEOXIT - designed for cleaning electric contacts. It is an aerosol and is cost about $15 for a small can. Radio Shack carried it - you may have to order it on line. Great stuff - a few short shots into your volume control and it fixes the problem. Trust me - this is the only thing that works without doing damage to the volume control.
              Ed

              Comment

              • Mark E.
                Extremely Frequent Poster
                • March 31, 1993
                • 4503

                #8
                Re: Radio crackles while turning volume knob- 1970 U79 stereo

                Originally posted by Gary Ramadei (14833)
                Hi Mark
                I have the same deal with my 72. I used Deoxit to spray down the pot shaft and it did help but I want to pull the radio when I get time and go through it.

                Here is a link to last year

                https://www.forums.ncrs.org/showthre...n-I-turn-it-on
                I saw this thread during my initial research, but thought it was only about a pop noise when turning on the radio. If I read further I would have learned about treating the crackling while adjusting the volume.

                It reads like an ad for DEOXIT. Sounds like good stuff.
                Mark Edmondson
                Dallas, Texas
                Texas Chapter

                1970 Coupe, Donnybrooke Green, Light Saddle LS5 M20 A31 C60 G81 N37 N40 UA6 U79
                1993 Coupe, 40th Anniversary, 6-speed, PEG 1, FX3, CD, Bronze Top

                Comment

                • Frank D.
                  Expired
                  • December 26, 2007
                  • 2703

                  #9
                  Re: Radio crackles while turning volume knob- 1970 U79 stereo

                  DeOxit is all I use now for connector cleaning and radio knobs. Its really good for spraying in those pesky bulkhead connectors near the master cylinder and cleaning up corrosion there...and in tail light/parking light sockets and anywhere else you can think off....like the rear harness connector behind the DS kick panel... Buy 2-3 cans....it can go fast once you figure out all of its uses...

                  Comment

                  • Ed S.
                    Extremely Frequent Poster
                    • August 6, 2014
                    • 1377

                    #10
                    Re: Radio crackles while turning volume knob- 1970 U79 stereo

                    Originally posted by Mark Edmondson (22468)
                    I saw this thread during my initial research, but thought it was only about a pop noise when turning on the radio. If I read further I would have learned about treating the crackling while adjusting the volume.

                    It reads like an ad for DEOXIT. Sounds like good stuff.
                    For the record - I don't have a vested or financial interest in DEOXIT other than the fact that I use it and it works better than advertised. I really is great stuff - hard to find these days.
                    Ed

                    Comment

                    • William F.
                      Extremely Frequent Poster
                      • June 9, 2009
                      • 1357

                      #11
                      Re: Radio crackles while turning volume knob- 1970 U79 stereo

                      Why not other brands of electrical contact cleaners? CRC mskes one.

                      Comment

                      • Ed S.
                        Extremely Frequent Poster
                        • August 6, 2014
                        • 1377

                        #12
                        Re: Radio crackles while turning volume knob- 1970 U79 stereo

                        Originally posted by William Ford (50517)
                        Why not other brands of electrical contact cleaners? CRC mskes one.
                        William, I don't know the answer to that question. What I do know is that Jerry Rudbeck, who retired from C2 radio repairs & restorations a few years ago and was (still is) regarded as perhaps the best radio technician around -- for early GM radios, highly recommended Deoxit.... and only Deoxit. Other stuff may work but for me, it is not worth the risk. I suppose if you compared ingredients on the labels - if they list the ingredients and they were the same there would be no difference. But again - why risk it.
                        Ed

                        Comment

                        • Joe R.
                          Extremely Frequent Poster
                          • May 31, 2006
                          • 1822

                          #13
                          Re: Radio crackles while turning volume knob- 1970 U79 stereo

                          William,

                          A friend of mine is an electronics technician and has been for probably 40 years or so. He swears by Deoxit also. There may be other products that work as well but I doubt it. It isn't all that expensive, so why take a chance?

                          Joe

                          Comment

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