I've been given this amp, along with 3 others, which i've already fixed and found that all of the supply mosfets were spectacularly exploded (pics included).
so i ordered replacements and with my new bench supply i can easily limit the current and voltage so the big components wont go boom instantly. (yay)
i've replaced the supply irfz44n's, checked the output transistors, speaker outputs, regulated supply output, rectifiers, and supply drive transistors. the amp will go into protect and draw as much current as i give it. while illuminating the protect light.
if you notice the wires soldered on the caps, i had my supply hooked up to see if it could get sound from the amp side, or if it would still pull all it can take. the power light comes on and sound comes through drawing little current. i had it probably at 10v/10v (since i dont know what it should put out)
i saw a few other forum threads with similar incident and one had shown the 494 to be bad. so i bring out my oscope and probe pins 9 and 10. dc coupled at various rates, i find that pins 9 and 10 show a steady 3.5v. (in reference to ground). at the gate of the transistors, both sets show a steady 2v at 500ma supply and steady 4v at 2A supply. i've only applied voltage for less than a second as not to burn out the precious irfz44n's as they get hot rather quickly at 2A (about 20w?).
so i ordered replacements and with my new bench supply i can easily limit the current and voltage so the big components wont go boom instantly. (yay)
i've replaced the supply irfz44n's, checked the output transistors, speaker outputs, regulated supply output, rectifiers, and supply drive transistors. the amp will go into protect and draw as much current as i give it. while illuminating the protect light.
if you notice the wires soldered on the caps, i had my supply hooked up to see if it could get sound from the amp side, or if it would still pull all it can take. the power light comes on and sound comes through drawing little current. i had it probably at 10v/10v (since i dont know what it should put out)
i saw a few other forum threads with similar incident and one had shown the 494 to be bad. so i bring out my oscope and probe pins 9 and 10. dc coupled at various rates, i find that pins 9 and 10 show a steady 3.5v. (in reference to ground). at the gate of the transistors, both sets show a steady 2v at 500ma supply and steady 4v at 2A supply. i've only applied voltage for less than a second as not to burn out the precious irfz44n's as they get hot rather quickly at 2A (about 20w?).
Attached Files