t_munz10
New Member
Hey Guys!
Some of you may remember, I was taking apart a CA-800 for cleaning to see if that would fix the very scratchy output.
I've cleaned all the pots and switches with Deoxit and have semi reassembled everything (enough to test). Looks like the cleaning helped a little, but I may still be in for a full recap and transistor replacements.
Now when I play music it is way clearer, almost static free. BUT it's waaaaaay to quiet and only one channel is working. Even at full volume it's not even near normal talking volume. I've check the biases on the main amp boards... and it doesn't look good.
I can set the differential and mid-point potentials correctly (15V and 0V respectively).
But when setting the idling currents using VR603 and VR604, while measuring on TP3 and TP4, the manual specs .047V for ClassAB and .8V for ClassA. I can adjust to a maximum of about .003V on the right (working) channel and I'm reading 0V regardless of adjustment on the left.
I didn't mess with the amp boards at all so I am a little confused as to what could have happened. Any ideas on what to troubleshoot here?
(EDIT: I should mention that I didn't measure the bias before cleaning, but the amp was much louder ... and noisier.)
Some of you may remember, I was taking apart a CA-800 for cleaning to see if that would fix the very scratchy output.
I've cleaned all the pots and switches with Deoxit and have semi reassembled everything (enough to test). Looks like the cleaning helped a little, but I may still be in for a full recap and transistor replacements.
Now when I play music it is way clearer, almost static free. BUT it's waaaaaay to quiet and only one channel is working. Even at full volume it's not even near normal talking volume. I've check the biases on the main amp boards... and it doesn't look good.
I can set the differential and mid-point potentials correctly (15V and 0V respectively).
But when setting the idling currents using VR603 and VR604, while measuring on TP3 and TP4, the manual specs .047V for ClassAB and .8V for ClassA. I can adjust to a maximum of about .003V on the right (working) channel and I'm reading 0V regardless of adjustment on the left.
I didn't mess with the amp boards at all so I am a little confused as to what could have happened. Any ideas on what to troubleshoot here?
(EDIT: I should mention that I didn't measure the bias before cleaning, but the amp was much louder ... and noisier.)