Connect with us

Quad 405 amp - output protection ?

Discussion in 'Electronic Repair' started by N Cook, Jun 24, 2004.

Scroll to continue with content
  1. N Cook

    N Cook Guest

    Straight across the output of each channel of this 1985 amp
    is a diac and triac, what and how do they protect anything ?

    electronic hints and repair briefs , schematics/manuals list on
  2. Mike Diack

    Mike Diack Guest

    You forgot to mention the resistor and capacitor.
    The R and C form a low pass filter - any DC that appears on the output
    (either polarity) passes through the LPF, and if above the trigger
    voltage of the"diac" (SBS actually) (around +/- 8 volts IIRC) triggers
    the triac and crowbars the output, at which point (hopefully) the rail
    fuses expire and your wooffer voice coil is saved from becoming toast.
    Clever circuit - saved my bacon on more than one occasion.
  3. N Cook

    N Cook Guest

    It makes sense now - i wasn't thinking about speaker protection.
    In internal failure as passing high level DC already we can assume that at
    one output tranny has failed or seriously biased-on so crowbarring
    more to fail a fuse or 2 makes sense
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day