I just wanted to quickly share how I repaired my NAD C160 preamp.
The issue is that regardless of the selected input, the sound still comes through from one of the others. In my case, even when other inputs were selected the sound from the CD input would continue to feed through to the power amp.
It took me a fair while to figure out what was going on, because at first I assumed the switching relay must be worn out. No it wasn't. To cut a long story short it was an issue with a small 10nF ceramic capacitor on the bottom left of the PCB which is part of the relay switching control circuit. There is one capacitor for each input.
When the capacitor fails, it goes low resistance and so partially pulls that relay on. Replace the capacitor, all better.
At the points marked in Blue, there should be about 3.2V for the selected input and 0V for the others. The input with an issue was giving 1.5V even when it was supposed to be off.
The issue is that regardless of the selected input, the sound still comes through from one of the others. In my case, even when other inputs were selected the sound from the CD input would continue to feed through to the power amp.
It took me a fair while to figure out what was going on, because at first I assumed the switching relay must be worn out. No it wasn't. To cut a long story short it was an issue with a small 10nF ceramic capacitor on the bottom left of the PCB which is part of the relay switching control circuit. There is one capacitor for each input.
When the capacitor fails, it goes low resistance and so partially pulls that relay on. Replace the capacitor, all better.
At the points marked in Blue, there should be about 3.2V for the selected input and 0V for the others. The input with an issue was giving 1.5V even when it was supposed to be off.
Attachments
I didn't expect it either. I was looking at them thinking the path was leading there... but there was also some bad looking electrolytics so I changed those before trying the ceramics. Turns out the bad looking electrolytics were actually fine (tested on my ESR meter afterwards) and the ceramic was duff! Particularly uncommon for non SMD ceramics isolated from board stress by the leads.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.