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NAD C320BEE - Bad capacitors?
NAD C320BEE - Bad capacitors?
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Old 14th June 2019, 12:07 PM   #21
Leolabs is offline Leolabs  Malaysia
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Quote:
Originally Posted by Holm422 View Post
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!
Alright,we can proceed further to +/-18V section,as the relay is supply by +18V.Try measure each pin voltage of Q41 and Q43 respective to ground.

Hopefully the real issue is not the MCU on the front panel.

Last edited by Leolabs; 14th June 2019 at 12:12 PM.
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Old 15th June 2019, 08:15 AM   #22
Holm422 is offline Holm422
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Quote:
Originally Posted by Leolabs View Post
Alright,we can proceed further to +/-18V section,as the relay is supply by +18V.Try measure each pin voltage of Q41 and Q43 respective to ground.

Hopefully the real issue is not the MCU on the front panel.
Q41
E 0.64V
C 0V
B 0V

Q43
E 0V
C 39V
B 0.50V

This, seems a bit wierd in my eyes. Any clues?
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Old 15th June 2019, 08:53 AM   #23
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Quote:
Originally Posted by Holm422 View Post
Q41
E 0.64V
C 0V
B 0V

Q43
E 0V
C 39V
B 0.50V

This, seems a bit wierd in my eyes. Any clues?
Try de-solder R45 and measure the ohms.
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Old 15th June 2019, 09:13 AM   #24
iaaeap is offline iaaeap  United Kingdom
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Quote:
Originally Posted by Holm422 View Post
Images of the area to the front of UPC1237 and the left (towards transformer) of Q41 and Q42.
I donít know much about the amp circuit but doesnít one of those soldered connections show signs of deterioration, possibly overheating? Maybe worth a closer look.
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File Type: jpg 464A3890-571A-42B8-A9AF-4C1A89F635B1.jpg (236.1 KB, 67 views)
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Old 15th June 2019, 03:44 PM   #25
Holm422 is offline Holm422
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Quote:
Originally Posted by Leolabs View Post
Try de-solder R45 and measure the ohms.
R45 desoldered
33,4 Ω, seems to be in spec (33R/0.5W 5% FS)


Quote:
Originally Posted by iaaeap View Post
I donít know much about the amp circuit but doesnít one of those soldered connections show signs of deterioration, possibly overheating? Maybe worth a closer look.
Could I just heat it and resolder, or would any component check of use?
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Old 15th June 2019, 03:54 PM   #26
Holm422 is offline Holm422
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It tested out okay, which means it is okay. But it looked a bit burned in the middle. Couldn't get the white balance exact, but this is a close up of R45.
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File Type: png R45.png (959.4 KB, 59 views)
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Old 16th June 2019, 07:28 AM   #27
Ian Finch is offline Ian Finch  Australia
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Quote:
Originally Posted by iaaeap View Post
..... doesnít one of those soldered connections show signs of deterioration, possibly overheating?....
That and several other solder joints there just appear to have excess flux and solder. They've probably been re-soldered a little too much, to ensure they were good.
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Old 16th June 2019, 07:40 AM   #28
Holm422 is offline Holm422
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Quote:
Originally Posted by Ian Finch View Post
That and several other solder joints there just appear to have excess flux and solder. They've probably been re-soldered a little too much, to ensure they were good.
Early (around 2006-07) the transformer was exchanged, through a servicecenter. Those days I was (very) young and had no real ambition to do DIY-repairs. If they de-soldered and re-soldered in the makes of fault finding or if it is factory - I do not know.

I've tried to measure different components throughout the mainboard, and the only thing that strikes me is that I can't really find any +/- 18V.

If any one has any suggestions where to continue the search for the bad component(s) I would be thrilled to measure, de-solder or swap parts.

Thank you!
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Old 16th June 2019, 08:43 AM   #29
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Quote:
Originally Posted by Holm422 View Post
R45 desoldered
33,4 Ω, seems to be in spec (33R/0.5W 5% FS)




Could I just heat it and resolder, or would any component check of use?
Now that's weird...if the resistor is ok,then the C pin of Q41 should have some voltages instead of zero.

Disconnect power and make sure all caps are discharged,measure the ohm from +18v to ground....u may get some low ohm reading initially (due to charging action the caps) but it will slowly rise up to higher ohm value.....If the ohm reading remain very low ohm all the time, then something is shorting the +18V rail.
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Old 16th June 2019, 09:24 AM   #30
Ian Finch is offline Ian Finch  Australia
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If you haven't already referred to the service manual schematic, it's here: NAD C320BEE - Manual - Stereo Integrated Amplifier - HiFi Engine
On the main board schematic diagram, the +/-18V power supply is in the lower L/H corner.
The supply is derived from the main power rails of +/- 37VDC and regulator transistors Q41,42 (TO126 size power transistors 2SD669/649) are the regulator transistors and the rest of the circuit controls them. The input at the collectors should be about +/-37VDC and the output at the emitters should be about +/- 18N respectively for Q41/42. Simple as that. Assuming that is the case, you then trace where they lead by their reference points, according to the schematic.

If you don't find those voltages anywhere else (such as the protection board and ISC circuit), then the standby control circuit probably prevents them being activated and the amplifier wont start up. It's complicated yes, but that's why there are trained service people.

If you are tracing voltages, it's wise to secure the common probe to ground properly with a hook probe, clip lead or terminal and only use one probe with the other hand clear of the works - not only for personal safety but its all too easy to slip and take out many semis in a flash when juggling two probes as well as set and read the meter whilst checking voltages. Take care - you may only get one chance with either type of risk.
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