Cpartipilo
Active member
Hi guys,
I'm back to ask for help!
I purchased a "broken" Isa428 which was blowing the fuse. Checked and the power transformer was overheating and drawing more current than it should which was the main problem. I ordered an original tranny from ThermalRelief and got the unit going.
So far so good, i'm testing channels until i got to channel 3. The channel has so much gain that without a mic connected i can still hear environment noise in my headphones. It's like if the box becomes a microphone, if i tap the case it sounds like if there was a mic inside of it.
If i plug a mic into that channel then it overloads wildly so i'm guessing is something in the gain control circuit (if there is such a thing in a preamp)
Schematics are not available but maybe someone can guide me in some general way as to what i should look for. I have 3 good channels so i could try to compare test points from the other channels.
Thanks!
I'm back to ask for help!
I purchased a "broken" Isa428 which was blowing the fuse. Checked and the power transformer was overheating and drawing more current than it should which was the main problem. I ordered an original tranny from ThermalRelief and got the unit going.
So far so good, i'm testing channels until i got to channel 3. The channel has so much gain that without a mic connected i can still hear environment noise in my headphones. It's like if the box becomes a microphone, if i tap the case it sounds like if there was a mic inside of it.
If i plug a mic into that channel then it overloads wildly so i'm guessing is something in the gain control circuit (if there is such a thing in a preamp)
Schematics are not available but maybe someone can guide me in some general way as to what i should look for. I have 3 good channels so i could try to compare test points from the other channels.
Thanks!