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Fender Frontman 212R

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  • #1

    Fender Frontman 212R

    Hope everybody is doing ok......a quick question....when this amp is first turned on, with no guitar connected, there is a very low buzzing sound in the speakers.....reminds me of an output stage issue with a leaky output component...but not enough to blow the fuse....and it is not affected by any of the controls.....However, if you insert a plug into either one of the input jacks, this low level buzzing goes away and the amp plays normally...the owner stated that the amp was working great and of course I did not power it up to test in before I took it apart.....I took his word for it..... stupid me.....anyway, I had to replace a broken reverb pot.....that's it.....anybody have any suggestions of what could be causing this buzzing sound....
    Cheers.......
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  • #2
    Sounds like the input jacks aren't getting a good ground of the signal unless the plug is installed and making contact with the switch contact. I'd recommend to clean the input jacks and see if the ground switch terminals are making solid contacts.
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    • #3
      I bet if you plug into the power amp in jack, it will also go away, just like the input jacks. Note that all three of those jacks have a break contact when plugged into and see upper left, it controles MUTE. Now look lower right at the input to the power amp. See MUTE there? I suspect your MUTE circuit is causing this. One question first. Are you using a bulb limiter? And if the amp is stable and not blowing fuses, why? Get it off the bub and see if it wakes up OK.

      Watch C47, is it charging right tup?
      Education is what you're left with after you have forgotten what you have learned.

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      • #4
        There was a thread about this issue. Has to do with the mute circuit. A fix you can try here: https://music-electronics-forum.com/...305#post588305
        Originally posted by Enzo
        I have a sign in my shop that says, "Never think up reasons not to check something."


        ​
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        • #5
          Originally posted by Enzo View Post
          I bet if you plug into the power amp in jack, it will also go away, just like the input jacks. Note that all three of those jacks have a break contact when plugged into and see upper left, it controles MUTE. Now look lower right at the input to the power amp. See MUTE there? I suspect your MUTE circuit is causing this. One question first. Are you using a bulb limiter? And if the amp is stable and not blowing fuses, why? Get it off the bub and see if it wakes up OK.

          Watch C47, is it charging right tup?
          not using a bulb limiter....I'll check it out again....

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          • #6
            Originally posted by g1 View Post
            There was a thread about this issue. Has to do with the mute circuit. A fix you can try here: https://music-electronics-forum.com/...305#post588305
            thanks g1

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