Well, I'm bored in isolation, so I'm going through my projects. I have an HK ca260 that exhibits very strange behavior. At very low volume (and I mean just a couple clicks up on a head unit.) The audio is very choppy, and weak. If you turn it up a bit, the audio comes through, but it's not right. I discovered that if you touch the can of the coupling capacitors the audio clears right up even at very low volume. (I was bending one over to put my scope probe on it) but of course it adds 60 cycle noise like crazy. I've replaced the coupling caps, and it may have helped a little, but not enough to brag about. These have a very strange power supply in them. Anyone have any thoughts? It's both channels, which screams power supply to me, but all the voltages are there and stable.
yes, and the source is on the same ground as the amp. I've tried 2 different head units and no change, I've even fed it straight 500hz signal from a generator. does the same thing.
If touching the caps clears it up, that should make it easier to see where the signal changes in the circuit.
What is the circuit board designation of the caps that you can touch to make a difference?
What is the circuit board designation of the caps that you can touch to make a difference?
If you touch them with an insulated probe does it make a difference?
If you touch either (one at a time) does it affect the other channel?
If you touch either (one at a time) does it affect the other channel?
touching them only affects the channel you're touching. I forgot to mention, that if you power it up with the remote already connected. Meaning just remove the main B+ in, and then Connect it, so it sees turn on at the same time, the audio is clear for about 1.5 seconds. and then drops off to it's choppy state.
At what point in the circuit do you see the change in audio when the caps are touched?
Does the position of any of the switches make a difference?
Does the position of any of the switches make a difference?
the switch positions make no change, aside from the volume level it takes to break the choppy/ static audio.
Oh, and the lower the frequency, the choppier it is. I'll look at the point where it changes again.
Oh, and the lower the frequency, the choppier it is. I'll look at the point where it changes again.
The signal changes glabally...all the way back to the input. Touching the can makes no difference with the scope probe.
It sounds like you have an open ground somewhere.
Is the change when touching the caps making a difference at the RCA signal input or shield ground?
Is the change when touching the caps making a difference at the RCA signal input or shield ground?