NAD C320BEE - Bad capacitors?

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Hello dear forum members!

I have a need for your assistance!

I have a NAD 320BEE (with the infamous JH capacitors). I have read about them on Badcaps.net and read threads on this forum (1 and 2) regarding similar issues.

I am now facing the orange/amber light not turning green. I powered it off with the remote and I thought it sounded a bit louder than usual. And the next morning when powering on, the orange light stayed fixed - indicating something was wrong. Pulled the cord, waited and reinserted the plug and powered on with no luck. Still orange light. Unscrewed the lid. At first I thought the caps in the power supply / filter area had leaked but learned that this is just glue. I do think one of the 15000uF cap is swollen. Maybe some other ones are discoloured on the "mainboard". Could you please advise on what I might be seeing/not seeing? Should I just try to replace the 15000uF 50V capacitors or should I try to recap all electrolytics (with the possibility of shortening something). Previous during the last few years I have been hearing the 50hz hum but thought this was from the potentiometer since raising or lowering the volume made it disappear for a while.

I have a DMM and a soldering station and some basic knowledges but I do need some help in understanding how to think in approaching this type of issue. Where to begin? I feel quite lost.

Thank you for your time and effort!


Best regards,
Holm422
 

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Hello,
The big capacitors seem to have a plastic black foil to cover the aluminium can. You could try removing that by carefully cuttting it into pieces with a small stanley knife to check if the capacitor is really swollen. Maybe you could check with infra red thermometer is the one that looks bad has a higher temperature? Greetings, Eduard
 
Check for DC on the output firstly. If it has had regular use then the capacitors are probably not at fault, like a car battery not being used. L11 and L21 is a good place to measure from.

Thank you for your reply and advice!

I checked the L11 and L21 with my DMM to DC, red on the coil and black on the chassi as ground. 0V on both, but when I put my probe on the L11 coil the black relay-looking thing produce a small jitter. Is this the way you inteded me to test? The 4 power supply fuses look good. What does this 0 V reading tell us, no power to the DC-side?

Hello,
The big capacitors seem to have a plastic black foil to cover the aluminium can. You could try removing that by carefully cuttting it into pieces with a small stanley knife to check if the capacitor is really swollen. Maybe you could check with infra red thermometer is the one that looks bad has a higher temperature? Greetings, Eduard

Thank you for your reply and effort to try to help me! I do have a IR-temperature meter but sadly no battery. Read about the plastic top, but do I dare to cut in to them?
 
Hi,just tell us between V+ and Gnd is how much and between V- and Gnd is how much.Dont worry about the polarity if you are using a Digital Multimeter.

Schematic is here :
https://3.bp.blogspot.com/-SShCymnrPYQ/V39T4-fWUjI/AAAAAAABXPM/2gejJGv8yrQni_-NfJ7H-7wztc_LJm2YACLcB/s1600/power%2Bamp.jpg

I used to own the later version,C325BEE which the muting fet was dead.....so far no problem after sold to my friend.

Thank you for the schematics, I've been looking at the Reptips.dk C320BEE Service manual and this was a bit more easy to read for beginners.

No need to. If the plastic cover alone is is bulged (as it often is) it will readily depress and return when you remove your finger. It the aluminium cap itself is bulged, you won't be able to depress the plastic cover, or not without considerable force, that is.

The plastic cover is not depressable, a fraction of a mm is all I could get it to depress with use of some (but not extensive) force.

I did do a bit of measurements, could someone help guide me in what to make of it?

The orange light means "security". I read on this french blog regarding issues with the security module (google translate) and this gave me some insight.

I measured CB47 (value specified in schematics)
Pin 1 -> Gnd
Pin 2 -> 5.6 V (5.6V)
Pin 3 -> -38.5 V (-37)
Pin 4 -> 38.5 V (37)
Pin 5 -> 0.13 V
Pin 6 -> 1.75 V --> C421 --> IC 44 PIN 4 [1.75V] (2.0V)
Pin 7 -> 0V

CB49
Pin 1 -> -38.5V (-46V)
Pin 2 -> -38.5V (46V)

IC44
Pin 4 -> 1.75V (2.0V)
Pin 8 -> 3,23V (3.25V)

C420 -> 1.98 (2.16V)


There seems to be a substantial difference on the CB49 (7.5V difference), could this voltage drop be the culprit? Also when investigating the security part of the board on the underside (around Q41, C420, C421 and the resistorbank sourrounding these the board looks a bit discolored (yellow/brownish). Could not wash this of with IPA.

Thank you for any input!
 
Thank you for the schematics, I've been looking at the Reptips.dk C320BEE Service manual and this was a bit more easy to read for beginners.



The plastic cover is not depressable, a fraction of a mm is all I could get it to depress with use of some (but not extensive) force.

I did do a bit of measurements, could someone help guide me in what to make of it?

The orange light means "security". I read on this french blog regarding issues with the security module (google translate) and this gave me some insight.

I measured CB47 (value specified in schematics)
Pin 1 -> Gnd
Pin 2 -> 5.6 V (5.6V)
Pin 3 -> -38.5 V (-37)
Pin 4 -> 38.5 V (37)
Pin 5 -> 0.13 V
Pin 6 -> 1.75 V --> C421 --> IC 44 PIN 4 [1.75V] (2.0V)
Pin 7 -> 0V

CB49
Pin 1 -> -38.5V (-46V)
Pin 2 -> -38.5V (46V)

IC44
Pin 4 -> 1.75V (2.0V)
Pin 8 -> 3,23V (3.25V)

C420 -> 1.98 (2.16V)


There seems to be a substantial difference on the CB49 (7.5V difference), could this voltage drop be the culprit? Also when investigating the security part of the board on the underside (around Q41, C420, C421 and the resistorbank sourrounding these the board looks a bit discolored (yellow/brownish). Could not wash this of with IPA.

Thank you for any input!

It's "Protection",although didn't know why google would translate it to "security".

Anyway,this amp is powered by dual voltage level,i.e. when lower power it's running at lower supply voltage,if needed,it will switch to higher voltage.As far as i can see,it's that currently the supply is symmetrical in both plus and minus.

Try measure L11 and L21(doesn't matter which pin since it's almost zero ohm for DC) voltage respective to ground ,we need to check the is there any significant offset voltage at output.
 
It's "Protection",although didn't know why google would translate it to "security".

Anyway,this amp is powered by dual voltage level,i.e. when lower power it's running at lower supply voltage,if needed,it will switch to higher voltage.As far as i can see,it's that currently the supply is symmetrical in both plus and minus.

Try measure L11 and L21(doesn't matter which pin since it's almost zero ohm for DC) voltage respective to ground ,we need to check the is there any significant offset voltage at output.

Thank you for helping me analyse the data!

As stated previously, the voltage on L11 and L21 is 0. Will test again tomorrow. What does this mean?
 
It's "Protection",although didn't know why google would translate it to "security".

Anyway,this amp is powered by dual voltage level,i.e. when lower power it's running at lower supply voltage,if needed,it will switch to higher voltage.As far as i can see,it's that currently the supply is symmetrical in both plus and minus.

Try measure L11 and L21(doesn't matter which pin since it's almost zero ohm for DC) voltage respective to ground ,we need to check the is there any significant offset voltage at output.

There is 0V at L11 and L21.

What further investigations/measurements can be done in order to narrowing down the issue? Do you see any good places to measure the 18V lines?

The relay never clicks, the amp is in stand-by/protection mode. Pressing the buttons on the front or pressing the remote changes nothing. What else could cause this?

All voltages to the IC44 seem to be within specification. See earlier post.

Thank you for taking your time!
 
There is 0V at L11 and L21.

What further investigations/measurements can be done in order to narrowing down the issue? Do you see any good places to measure the 18V lines?

The relay never clicks, the amp is in stand-by/protection mode. Pressing the buttons on the front or pressing the remote changes nothing. What else could cause this?

All voltages to the IC44 seem to be within specification. See earlier post.

Thank you for taking your time!

Well,we can say at least the power amp section is intact.Possibly the protection circuit itself or the supply voltage switching section is having issue.

Anyway,I'll try to take a look again on the full service manual and get back to you.
 
Try measure AC voltage BETWEEN C41's pin and AC voltage (respective to ground) before D413.

C41 pin, hard to reach with the power supply board hooked up (short cables). I am not sure I managed to squeeze in between the fuses, since I only read 0V. The F41 and F42 read 28V AC. F43 and F44 read 36V AC. I managed to short F41 and F42 when trying to get to C41. It seems as if nothing blew up. Phew. Will have to check C41 with board out of the case.

D413 reads 3 V on one side (SILVER) and 2.2V on other side (BLACK). Low?

On the transistors Q41 and Q42 the emitter sides doesn't have 18V.
 
C41 pin, hard to reach with the power supply board hooked up (short cables). I am not sure I managed to squeeze in between the fuses, since I only read 0V. The F41 and F42 read 28V AC. F43 and F44 read 36V AC. I managed to short F41 and F42 when trying to get to C41. It seems as if nothing blew up. Phew. Will have to check C41 with board out of the case.

D413 reads 3 V on one side (SILVER) and 2.2V on other side (BLACK). Low?

On the transistors Q41 and Q42 the emitter sides doesn't have 18V.

Ok,seems like all AC rail is functioning well,so we can move on the AC DET ,try remove only that particular pin,check if the (D413)voltage will go up or not,who knows might be only simply a faulty UPC1237,but of course we need to confirm.

Try measure those pin voltages on UPC1237 too.

And you won't get any output from Q41 and Q42 as both will shutdown during standby/protection mode.
 
Ok,seems like all AC rail is functioning well,so we can move on the AC DET ,try remove only that particular pin,check if the (D413)voltage will go up or not,who knows might be only simply a faulty UPC1237,but of course we need to confirm.

Try measure those pin voltages on UPC1237 too.

And you won't get any output from Q41 and Q42 as both will shutdown during standby/protection mode.

First off: Thank you for taking your time and trying to help me. I am learning as well.

Removed the AC-DET pin from CB47.
D413 voltage 27.9V AC (black side) and 27.5V AC (silver side)

IC44 (UPC1237)
Pin1 0V
Pin2 80mV
Pin3 0V
Pin4 1,75V (specified 2.0V)
Pin5 0V
Pin6 0,5V (output)
Pin7 2,0V (specified 2.16V)
Pin8 3,25V (specified 3,25V

(UPC1237 associated capacitors)
C420 - 2.0V
C421 - 1,75V
C422 - 80mV

The voltages on the UPC1237 seem to be right. But looking on the underside of the board checking the voltages I see an area that is discolored (see attached image). I do not own an Atlas DCA or Mega328 so I can't really check the capacitors in any more formal way. Otherwise the voltages of the UPC1237 (IC44) seem pretty correct? But is 0,5V output correct?

Removed the rectifier board, to mesaure C41, but removing the grounding (closing) screw and lifting it from the case it is not allowing power to flow. And I do not have those small insulated alligator clamp-style probes (I am trying to find some one here that sells them) so the C41-readings cannot be considered as definitive.

What do you think? Any next steps?
 
First off: Thank you for taking your time and trying to help me. I am learning as well.

Removed the AC-DET pin from CB47.
D413 voltage 27.9V AC (black side) and 27.5V AC (silver side)

IC44 (UPC1237)
Pin1 0V
Pin2 80mV
Pin3 0V
Pin4 1,75V (specified 2.0V)
Pin5 0V
Pin6 0,5V (output)
Pin7 2,0V (specified 2.16V)
Pin8 3,25V (specified 3,25V

(UPC1237 associated capacitors)
C420 - 2.0V
C421 - 1,75V
C422 - 80mV

The voltages on the UPC1237 seem to be right. But looking on the underside of the board checking the voltages I see an area that is discolored (see attached image). I do not own an Atlas DCA or Mega328 so I can't really check the capacitors in any more formal way. Otherwise the voltages of the UPC1237 (IC44) seem pretty correct? But is 0,5V output correct?

Removed the rectifier board, to mesaure C41, but removing the grounding (closing) screw and lifting it from the case it is not allowing power to flow. And I do not have those small insulated alligator clamp-style probes (I am trying to find some one here that sells them) so the C41-readings cannot be considered as definitive.

What do you think? Any next steps?

Don't worry about the C41 voltage reading anymore since u already measure those near at the fuse area.The AC-DET reading is normal too,we can move further.

The colored PCB track on the +/-18V power supply section is consider normal, since the input is around +/-37V,meaning there will be a 19V drop across those transistor,lots of heat will be generated under normal operation.

Now try measure DC voltage respective to ground on pin 1 and pin 2 of CB45.
 
Don't worry about the C41 voltage reading anymore since u already measure those near at the fuse area.The AC-DET reading is normal too,we can move further.

The colored PCB track on the +/-18V power supply section is consider normal, since the input is around +/-37V,meaning there will be a 19V drop across those transistor,lots of heat will be generated under normal operation.

Now try measure DC voltage respective to ground on pin 1 and pin 2 of CB45.

Hi!

Good not needing to worry about the heatassociated discoloring.

CB45
Pin 1 0,49V (also labelled JDD)
Pin 2 0,49V (also labelled JDK)

So CB45 pin 1 is from IC44 pin 6, since the datasheet for UPC1237 says pin 6 is output pin of relay driver.

Tried to trace Pin 2 from CB45 and it is going to L21 and relay?

Is it the relay thats not switching? Or is it the UPC1237, read it closes the relay in order to prevent speaker disconnect shock. And the night I turned it off the last time, I though it sounded more agressive. Pin 3 is also stated to be the reset pin of the UPC1237, any ways to feed a reset signal and see if it works?

This is way more complicated, and interesting, but does it seem we can make her chooch again?

Thank you for spending time and effort in order to help me! Much appreciated!
 
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