Timbergetter
New Member
I had been suffering the erratic performance of my NAD C352 amp for about a year until it died, so I finally decided to open it up recently to see what I might be able to do to improve things. What I found was very similar to the discoveries in this post:
https://audiokarma.org/forums/index...ng-protection-mode-on-volume-increase.954805/
The overheating area was as bad if not worse than that depicted there. The overheating had badly damaged the bonding of circuit tracks to the board and there were a great many cracked solder joints including the anchor points for the main heat sinks.
I painstakingly re-glued or replaced all the circuit board tracks that had lifted using JB Weld. I then replaced every last JH capacitor with a mix of Panasonic and Nichicon caps. The only 22,000 mf caps in the power supply I could find that would actually fit in the space available were of uncertain origin (JCCON) but they came up ok when tested. I used JB Weld again to bond wobbly heat sinks to the PCB and did a solder reflow on all suspect joints.
After all this effort the amp would not come to life when powered on. I tracked this down to a blown diode in the standby power regulator circuit (D401) which I replaced. At this stage the amp would intermittently start to power up but not to an operating state. Further investigation found a cracked solder joint on the P101B connector on the main board. Fixing this resulted in the C352 bouncing back to life as good as new.
There is still more heat present in the area that suffered previously. I measured the following:
Q155 66ºC
R281 100ºC
R245 88ºC
Does anyone have any suggestions for cooling this area down?
The schematics in the service manual were invaluable in support of this exercise. Nevertheless the diagrams do suffer from missing connections, labelling and subtle differences when compared to what was actually installed. All in all it was a worthwhile undertaking and I look forward a few more years of service from this amp that I have had since new in about 2005.
https://audiokarma.org/forums/index...ng-protection-mode-on-volume-increase.954805/
The overheating area was as bad if not worse than that depicted there. The overheating had badly damaged the bonding of circuit tracks to the board and there were a great many cracked solder joints including the anchor points for the main heat sinks.
I painstakingly re-glued or replaced all the circuit board tracks that had lifted using JB Weld. I then replaced every last JH capacitor with a mix of Panasonic and Nichicon caps. The only 22,000 mf caps in the power supply I could find that would actually fit in the space available were of uncertain origin (JCCON) but they came up ok when tested. I used JB Weld again to bond wobbly heat sinks to the PCB and did a solder reflow on all suspect joints.
After all this effort the amp would not come to life when powered on. I tracked this down to a blown diode in the standby power regulator circuit (D401) which I replaced. At this stage the amp would intermittently start to power up but not to an operating state. Further investigation found a cracked solder joint on the P101B connector on the main board. Fixing this resulted in the C352 bouncing back to life as good as new.
There is still more heat present in the area that suffered previously. I measured the following:
Q155 66ºC
R281 100ºC
R245 88ºC
Does anyone have any suggestions for cooling this area down?
The schematics in the service manual were invaluable in support of this exercise. Nevertheless the diagrams do suffer from missing connections, labelling and subtle differences when compared to what was actually installed. All in all it was a worthwhile undertaking and I look forward a few more years of service from this amp that I have had since new in about 2005.
