K4020

Kits Audio Hi Fi Projects
1

Some years ago I assempled the K4020. It works fine, but there’s one problem which has been there now for about 2 years:

The “click” sound, normally occurring a few seconds after I switch the unit on, occasionally keeps comes back, in one of the channels, at irregular intervals (sometime infrequent, sometimes a number of clicks). The problem is there also if I swap the loudspeakers (and also at very low volumes - no CD being played), so I do believe that this is due to a K4020 component.

I guess that the problem is related to the automatic protection system. RY1 coming on and off, but why? Could somebody please advice me on how to solve this problem?

2

Hard to tell without actually being able to examine the amp. Furthermore, if it happens occasionally, it will be difficult to troubleshoot.
If I remember well, we’ve changed zener diodes ZD5 & ZD7 from 39V to 43V, it had something to do with unwanted tripping of the DC protection. You might want to give this a try.