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Thread: Acoustic 370 troubleshooting.

  1. #1
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    Acoustic 370 troubleshooting.

    i recently acquired an old 370 head in an alley and assumed it would be pretty bad off, but it sounds alright, just much quieter than it should. i love 370s and would like to get this freebie running, but need some pointers in the right direction.

    the 300 hz fader does nothing, but i think that the problem is in the output. tone and dynamics sound alright untill the volume pot is at about 10 oclock (but the amp still should be louder from the get go). once at 12 oclock and higher, the output "ducks" down when a loud note is played. it sounds like there could be a bad connection somewhere because the sound changes once in a while, but still it should be alot louder. i resoldered a few things, and didnt see anything obviously wrong.

    glad to answer any questions. any help would be greatly appreciated!

  2. #2
    Senior Member Enzo's Avatar
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    Clean the cutout contacts on all the jacks, in particular the patch jacks - send and return jacks - on the rear.

    Dead EQ slider? Probably the slider itself.

    See all those little 1uf electrolytic coupling caps throughout the circuit? Replace them.

    Your ducking sounds to me like a DC problem. See if it remains after recapping.
    Education is what you're left with after you have forgotten what you have learned.

  3. #3
    Member johnk_10's Avatar
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    i can practically guarantee that the eq slider is fine but the 1.5H inductor on the 300hz eq section is dead (reading open).they have a very common habit of going bad. i've been repairing a bunch of old acoustics lately and whenever a band isn't working, the inductor is the first thing i check and every single time it was the problem. their original eq inductors have been unobtanium for years but you can use a Mesa boggie 1H inductor and replace the .15 capacitor in series with it with a .22 cap and it'll be almost the exact same frequency (now 339hz as opposed to the original 335hz). and the mesa inductor fits the pcb perfectly.

    as for you volume issue, that's another problem altogether.

  4. #4
    Senior Member Enzo's Avatar
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    Well, there you go, two contrasting views. Either one easy to test for.
    Education is what you're left with after you have forgotten what you have learned.

  5. #5
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    ... and quite possibly both are right. Never decide that there's only one problem until you prove it.

  6. #6
    Supporting Member Jazz P Bass's Avatar
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    I had an EQ band on an Acoustic where the capacitor was not even there.
    Fell out, removed, not stuffed at the factory.
    Who knows?

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