Home › Forums › Help/Technical Questions › Vintage Small Stone Oscillation With Color Switch Up

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  • January 6, 2016 at 8:19 pm #84221
    Gristlepig
    Member

    Hey folks,

    I’ve got here a 1980 Small Stone which is giving me some grief…

    It works fine and sounds great, EXCEPT when the color switch is in the UP position. Then it makes a hella loud whistle as the phase reaches the the top of it’s sweep. I can’t locate a schematic, because I can’t determine which version this is… And on top of that, none of the part numbers are labelled on the PCB.

    I apparently can’t post pics as it is telling me they are too large, and I don’t have a way to shrink them on my ipad…

    The board is brown and has 5 OTA’s labelled EH1048
    The solder side of the board is marked with TCI-A4H 94HB and EH-4800 further down.

    Any help you guys might be able to offer would be greatly appreciated!!!

    January 9, 2016 at 1:04 am #121159
    Gristlepig
    Member

    Wow…

    Pretty useless posting this here I guess…

    January 12, 2016 at 4:24 pm #121164
    Scruffie
    Member

    Don’t get snippy, it’s off putting.

    Here’s your schematic http://www.freeinfosociety.com/electronics/schematics/audio/pictures/smallstonephasereffect.jpg

    The colour switch does two things, increases the sweep width and introduces feedback to the input of the circuit.

    Is this a problem the unit always had or one that developed over time? It sounds like it’s just too much feedback causing the issue but if it’s something that developed then that points to a part going bad rather than an issue of your particular unit.

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