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NAD C326BEE Recap

rolleiman

rolleiman

Active Member
Hi All,
I just purchased a NAD C326BEE that has never been used but has been stored in a closet for several years. I should be getting the unit tomorrow and was wondering the value of recapping the unit. From photos, they look like low grade caps and being several years old, not sure of the reliability.
I have done several vintage units and of course the sound improvements have been very good but was not sure about what the impact would be on a newer unit.
Anyone actually recapped one of these?
Thought?
 
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Compared my C326BEE with a C325BEE this week. Not too happy with my newer unit but will give it some time before modifying it.
 
It would be nice to be able to chat with the designer to see what parts he/she would have used if cost was not the driving factor. It seems to be opening up a bit after several hours of play but will see how she sounds in a few more weeks before I get the chainsaw (or perhaps my solder sucker) out and go to work.
What Caps are you partial to for power supply and audio path circuitry?
It looks like the designer bypassed the electrolytic caps in the audio path with small poly caps which is a good thing.
 
When I recap , I usually use kemets or chemicons for large psu then pana fc/fm or nichicon pw/he for most else, apart from low leakage use nichicon kl here and signal path I use elna rfs.
 
E78486D7-B63E-4DAE-BDA1-2B46B01588A2.jpeg 8C202B72-045D-48EA-B923-CC176684E910.jpeg

I have included a schematic of the PSU board and a zoomed in view of a pair of capacitors.
Questions:
1) why are C605 and C606 not the same value on the plus and minus 37V voltage rails?
2) will increasing the capacitance of C601 and C602 improve the bass response?
3) if any of these cap values are increased, is there a danger of too much inrush current?
 
C605 and c606 supply the low voltage parts of this amplifier +/-18v and +/-12v etc the reason why c605 is higher in value is that it also supplys +5v to the IC'S as well so the current demand is higher on that rail. Going up 1 increment in value won't matter for inrush current but physical size of the caps might and no these won't affect bass response.
 
Now that the amp has been burned in with lots of listening time it sounds very good thru my large Advent speakers so may not upgrade the caps at this time. Amazing what a little patience will do.
:-)
 
Well I am doing this recapping as we speak, power supply is already done, made a huge difference! - I may use the Silmics on the two pre-amp boards. You can call me crazy, but I just can't have 100% Chinese crap caps in a nice amp, every damn cap in the amp is Chinese no-name, so this is about to be 0% Chinese! and 100% audio-grade Japanese electrolytics. Also, you probably want to do several factory updates/mods, depending on your serial number, while you are in there. Several of them have to do with it going into protection for no reason. Fortunately, NAD provides nice underneath access door on bottom of amp for recapping.
 
Recapping this amp, I purchased caps based on the parts list from the NAD 326BEE Service Manual. It happens that some of the factory caps differ in voltage specs.

I purchased high quality Nichicon Gold Tune LKG 15000uf 50V caps. The factory installed KSC 15000uf 63V.

Should I, or is it safe to just install the new 50V caps or should I get 63V replacements?
 
kcidgib said:
Should I, or is it safe to just install the new 50V caps or should I get 63V replacements?
Click to expand...
Welcome aboard AK.. Should have asked this question before purchasing the Nichicons.;) Rule of thumb. Can go higher in voltage. Don't go lower..Looks like the supply is running right around +/- 46 vdc.. 50v is not much cushion room.
 
Last edited:
Thanks for the reply :) I guess I already knew the answer, I was so excited about starting and then so disappointed when I saw the caps on the board.

Lesson is don't forget to reference the caps on the board and not just the service manual before making an order.

Cheers!
 
So, the recapping sounds great as the caps have settled in with about 20 hours of play time. Now, trying to adjust the amp. When testing the voltage across TP1 & TP2 the trim pot adjusts as expected and can set a reading of 3.2mV for the L channel, but the voltage across TP3 & TP4 no matter how far I turn the trim pot the voltage is too low at idle to get a reading. It sounds okay still but just concerned there is a problem I'm not able to detect with just my ears or a voltage meter. Maybe a bad trim pot and my R channel is getting a zero idle adjustment?
 
Update: replaced the trim pot and now able to set voltage to spec. Also, careful to avoid cooling the unit unintentionally by having a fan nearby as that affects the voltage readings.
 
reddish75 said:
I haven't recapped but repaired one of these, I remember poor quality caps being used from oem.
Click to expand...

Hello,
My NAD C326BEE has an issue that is apparently common : It regularly falls into protection mode, ether at power on, or randomly.
The power LED then blinks RED, then after some time it goes back to working mode ... Some time it happens so often the amplifier is simply unusable.
I got the service manual, as well as three service bulletins about power cycling issue, but after checking all mods are already applied.
My amp SN is K24C326G38359
I am a bit stuck. I checked bias, I checked all signals input to the CPU that could trigger the decision to go into protection mode... may be the issue is around PSU as I see that one of the two main 15KuF caps is slightly inflated on the top.
As you say you have already an experience repairing this amp, I dare to ask you if you have an idea.
If I had to recap partially, what caps should I change ?
Thks and sorry to disturb
Philippe / France
 
LETOILE said:
Hello,
My NAD C326BEE has an issue that is apparently common : It regularly falls into protection mode, ether at power on, or randomly.
The power LED then blinks RED, then after some time it goes back to working mode ... Some time it happens so often the amplifier is simply unusable.
I got the service manual, as well as three service bulletins about power cycling issue, but after checking all mods are already applied.
My amp SN is K24C326G38359
I am a bit stuck. I checked bias, I checked all signals input to the CPU that could trigger the decision to go into protection mode... may be the issue is around PSU as I see that one of the two main 15KuF caps is slightly inflated on the top.
As you say you have already an experience repairing this amp, I dare to ask you if you have an idea.
If I had to recap partially, what caps should I change ?
Thks and sorry to disturb
Philippe / France
Click to expand...

Does the top of the cap press down when you press on it? Unplugged and voltage drained before this of course
 
Just for general information on this unit, the C326BEE was retired in about 2016 or so. I've owned two of them. Since this Nad model is at the most 10 or 11 years old, it does not need to be recapped, unless the caps have failed. My units ran just fine and I never heard any talk of substandard caps on this version. The earlier models did have some issues, the C372 had an early run with cap issues that was resolved. The C326BEE was a great little unit that sounded better than the price point for sure.

If you have ANY amp in storage for a few years, like the OP(now a couple of years ago), yes it will probably sound off at first. That's because you need to gently run it in for several hours before using it. Storage is not great for electronics, or caps anyway.
 
LETOILE said:
Hello,
My NAD C326BEE has an issue that is apparently common : It regularly falls into protection mode, ether at power on, or randomly.
The power LED then blinks RED, then after some time it goes back to working mode ... Some time it happens so often the amplifier is simply unusable.
I got the service manual, as well as three service bulletins about power cycling issue, but after checking all mods are already applied.
My amp SN is K24C326G38359
I am a bit stuck. I checked bias, I checked all signals input to the CPU that could trigger the decision to go into protection mode... may be the issue is around PSU as I see that one of the two main 15KuF caps is slightly inflated on the top.
As you say you have already an experience repairing this amp, I dare to ask you if you have an idea.
If I had to recap partially, what caps should I change ?
Thks and sorry to disturb
Philippe / France
Click to expand...

Did you ever solve this?
 
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