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I have a NAD C272 amp which died recently and I’m trying to test it to determine what needs to be replaced for it to work again but I’m a bit of electronics beginner so bear with me! I’ve read a lot about problems with this model, mostly with the main capacitors and transistor Q712. Most of these issues are discussed or mentioned in this thread:

https://www.diyaudio.com/forums/soli…refresh-5.html

However, my unit has the upgraded 100v capacitors and also the same updates as MaxMartin lists in the thread regarding his unit:

“I have myself a C272 of the newest batch from 2009. They’ve made some changes regarding transistors. Q710, 711 is 2240 and q712 is a970. On left and right boards there is now also 1220 and 2690 (input stage) like down in the +68v regulator. The 2240 pair and the 970 goes very hot still.. “
—MaxMartin

Apparently, NAD updated the later units with these modifications in response to problems the 272/372 series were having.

Ok, with that preface out of the way, the problem I have is the unit simply stopped working. No noise or other problems; it just has no output. The unit will power up meaning that the LED comes on when the power switch is pressed and it still clicks as it always did but there is no sound. I assume this points to the power board. I’ve looked closely at all parts inside the unit and have found no obvious problems or evidence of high temps. Everything looks normal.
So I tested the main power supply on the power board and it checked out fine. +68.7v and -68.6v in the appropriate places. However, there are also 2 more sets of test poles, one labeled “CB716, M- Test” and the other “CB717, M+ Test.” I could not get a reading from either of these. And what does the CB716 signify? Every test site has a unique CB number.
Here are some pics in case I’m not describing in appropriate ways:

Attachment 974166
Here is the overview with the power board towards the top and the large 4 capacitors.

By the way, my power board is labeled as Version 5.0 as I guess there are different versions that NAD used to combat the capacitor and transistor issues.

Attachment 974167

At the top left is the site where I measured +68v and -68v so the board is getting the correct power. However, the other test site M- in the photo measured 0 as well as the M+ site in the following photo. I assume these should be -68v and +68v respectively but hopefully someone out there can help me in measuring the test sites properly.

Attachment 974168

Attachment 974169

I also measured the 18v (CB723) test site but again, readings were 0. The other site I did not measure as I’m not sure what it is. What is a “P Test?”

Oh, and here is the factory service info for the 272:

Attachment 974172

Thanks in advance for any help you can give regarding this amp.