Nakamichi CA-5 hum/buzz and does anyone have the schematics/service manual?
My Nak preamp has had a hum that goes up with volume control for quite some time. Frequency seems to be at 60Hz.
I checked the ±24V rails and no superimposed AC is left on them, nice flat DC, so I ruled out the smoothing caps as a problem.
What ticked me off was a couple of actual grounding issues that I fixed, but that did NOT fix my hum.
I found out that if I ground the selected input pin, the hum goes away. I check with my scope and my input pins seem to pick up a light 60Hz. I guess I could check for cracks and such in pcb traces as all components seem well connected and in good shape.
Any suggestions of where to look?
I always manage to dig up a copy of schematics or service manual of most gear I own or work on, but this one, nothing! I'd really appreciate if someone with a copy could help me out
Thanks in advance!
Here is the service manual for CA-5:
Better use "save as" and download the file.
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