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NAD C320BEE - Bad capacitors?
NAD C320BEE - Bad capacitors?
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Old 11th June 2019, 08:04 AM   #11
Holm422 is offline Holm422
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Quote:
Originally Posted by Holm422 View Post
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?
Rechecked today. 0V on L21 and L11.
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Old 12th June 2019, 08:14 AM   #12
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Originally Posted by Leolabs View Post
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!
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Old 12th June 2019, 10:04 AM   #13
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Quote:
Originally Posted by Holm422 View Post
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.
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Old 12th June 2019, 10:15 AM   #14
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Try measure AC voltage BETWEEN C41's pin and AC voltage (respective to ground) before D413.
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Old 12th June 2019, 11:09 AM   #15
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Originally Posted by Leolabs View Post
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.
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Old 12th June 2019, 05:30 PM   #16
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Quote:
Originally Posted by Holm422 View Post
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.
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Old 13th June 2019, 09:13 AM   #17
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Originally Posted by Leolabs View Post
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?
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Old 13th June 2019, 09:25 AM   #18
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Default Images

Images of the area to the front of UPC1237 and the left (towards transformer) of Q41 and Q42.
Attached Images
File Type: jpg krets00000003-text.jpg (374.2 KB, 90 views)
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Old 13th June 2019, 12:06 PM   #19
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Quote:
Originally Posted by Holm422 View Post
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.
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Old 14th June 2019, 11:19 AM   #20
Holm422 is offline Holm422
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Originally Posted by Leolabs View Post
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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