No issues
Hey all,
Just wanted to touch back in and let you know this NAD is still in place and running. No further issues have ever come up.
Thanks everyone for the help!
- C
Hey all,
Just wanted to touch back in and let you know this NAD is still in place and running. No further issues have ever come up.
Thanks everyone for the help!
- C
That's bad planning from NAD.
Stabilize from +/- 55 volt to +/- 26 volt: this is bulls...t!
Of course i'ts gonna be hot.
My C556BEE the same.
Especially with DAC module the result is dramatic.
( DAC module powered also from +/- 26 volts! )
Very hot Q41, Q42 heatsinks, very hot D110,D111 Zeners, browned PCB, etc, etc.
Answer from NAD: this is normal...
Oh shure!😀 😀 😀
Stabilize from +/- 55 volt to +/- 26 volt: this is bulls...t!
Of course i'ts gonna be hot.
My C556BEE the same.
Especially with DAC module the result is dramatic.
( DAC module powered also from +/- 26 volts! )
Very hot Q41, Q42 heatsinks, very hot D110,D111 Zeners, browned PCB, etc, etc.
Answer from NAD: this is normal...
Oh shure!😀 😀 😀
Well, NAD isn't known for high grade, top shelf products and it would be dreaming to expect it at their budget price levels. Hence power management is done the cheapest, reliable way that meets warranty and reasonable product lifetime requirements. The browning of the PCBs by the way, is actually the discolouring of the type of the heat-sensitive dyestuffs used to colour them green, blue or shades between. That does not necessarily mean that the epoxy resin in the PCB is damaged.
If you're interested in the aesthetics of the insides of consumer electronics, I'd go upmarket.
If you're interested in the aesthetics of the insides of consumer electronics, I'd go upmarket.
This is my C356BEE.
You see on the pictures, the PCB is blistered, which means that the epoxy carrier is also damaged by excessive heat.
If you think this indicates normal warming and just discoloration, then i would ask where did you learn this profession?
An idiot who send 30 volts different to an linear power supply input! (Efficiency?)
Would it have been too expensive to make another transformer coil with lower voltage?
In C375BEE is good solution. Input voltage +/-36 volts. (attached schematic)
Why wasn't that good?
By the way, I've seen some amplifiers inside for the past 15 years.
This is an Ecler PA amplifier in my workshop for repair.
(Sorry for my bad english!)
Attachments
Blistered and charred boards are obviously damaged, not just discoloured, which is all I referred to. For a thermosetting plastic substrate like FR4 Epoxy/fibreglass to blister, it suggests extreme temperature conditions rather than a protracted overheating problem. I've not seen it here in local or imported audio gear - only in cheap industrial power supplies. One consistent blistering fault I witnessed was actually due to substandard PCB materials (uncured resin) and all the traceable units were replaced under warranty.
If you're unhappy with NAD's design philosophy, then take the matter up with them. I'm no apologist for their manufacturing philosophy and I have never liked working on the products from the days of the first 3020 model. I don't like it either but strong sales drive business - especially low price, high sales volume business.
Its not surprising that C356, C375 & 3020 designs are all credited to the same lead designer, B-E Edvardsen. So, if some of the relevant models seem OK and others not, then the problem is matter of deliberate budget compromises - perhaps bigger ones than anticipated.
If you're unhappy with NAD's design philosophy, then take the matter up with them. I'm no apologist for their manufacturing philosophy and I have never liked working on the products from the days of the first 3020 model. I don't like it either but strong sales drive business - especially low price, high sales volume business.
Its not surprising that C356, C375 & 3020 designs are all credited to the same lead designer, B-E Edvardsen. So, if some of the relevant models seem OK and others not, then the problem is matter of deliberate budget compromises - perhaps bigger ones than anticipated.
It’s consumer gear. That’s why they use single-sided PCBs. That’s why they cut corners absolutely everywhere. Putting 36V into a 15V reg is completely par for the course. It resulted in a saving of a couple of dollars per unit in parts. If it means the amp fails after five years, then all the better.
Don’t pretend it’s just NAD though. Every consumer electronic item I’ve ever worked on has been pretty-much the same. They’re all selling to the same market and that market cares only for price and loudness.
Don’t pretend it’s just NAD though. Every consumer electronic item I’ve ever worked on has been pretty-much the same. They’re all selling to the same market and that market cares only for price and loudness.
I just got a 'not working' NAD 356 (same amp as in this discussion)....a project for passing the time in COVID-19 precautionary 'stay at home' isolation. First time I've felt the need to wipe down and disinfect an amp I've gotten. (the seller was wiping down the amp and my money also, so we're both being careful.
The +/- 55v supply seems to be OK but the -26 and -18 rails are not - just reading a few tenths of a volt.
The same area of the PCB is burnt in my amp.
I've got some parts on order and I'll probably start a new thread/discussion once I have more ideas. I'm looking around Q44 and Q42 but I don't understand much about SS devices, so it should be fun to learn something new. (Tube amp troubleshooting is a lot simpler...).
Some work has already been done on the amp, but nothing very obvious is wrong from that.
Stay tuned!
The +/- 55v supply seems to be OK but the -26 and -18 rails are not - just reading a few tenths of a volt.
The same area of the PCB is burnt in my amp.
I've got some parts on order and I'll probably start a new thread/discussion once I have more ideas. I'm looking around Q44 and Q42 but I don't understand much about SS devices, so it should be fun to learn something new. (Tube amp troubleshooting is a lot simpler...).
Some work has already been done on the amp, but nothing very obvious is wrong from that.
Stay tuned!
Maybe start with a fresh R46, 51 ohm, maybe 2 Watt, fusible if you can get it -- in case I miss catching up with you on 'the other / your new' thread.
Both the -26V and -18V rails are supplied by R46, and if yours is like CraigP's, its popped open.
Cheers
Both the -26V and -18V rails are supplied by R46, and if yours is like CraigP's, its popped open.
Cheers
Thanks, Rick.
In mine it was the regulator transistor that was the problem.
I'm trying to figure out how to adjust the idle next.
I started a new thread:
https://www.diyaudio.com/forums/solid-state/351747-nad-c356bee-repair-adjustment-question.html#post6135966
In mine it was the regulator transistor that was the problem.
I'm trying to figure out how to adjust the idle next.
I started a new thread:
https://www.diyaudio.com/forums/solid-state/351747-nad-c356bee-repair-adjustment-question.html#post6135966