Hi Guys,
Having a bit of an issue with an amplifier I'm trying to troubleshoot. It has a reading of 0.300v on the right hand channel and I believe this is causing the amplifier to not turn on. Its just orange light.
Here what I know and what I have done:
The bias seems to increase on both channels just fine
The DC on left channel measures around 60mv at L21
The DC on right channel measures around 0.3v at L11
Q16,17,18,19 was swapped with working (?) channel
Emitter Q19 to Collector Q17 measures -28. other channel -38
R123 measure 0.3v
R115-116 where they meet also measure 0.3v
Not a single bad resistor! (I measured personally
)
Already been fully recapped but problem persists..
Thats as far as mine and my friends (owner of Nad) ability goes to troubleshoot this..
Any help appreciated..
Having a bit of an issue with an amplifier I'm trying to troubleshoot. It has a reading of 0.300v on the right hand channel and I believe this is causing the amplifier to not turn on. Its just orange light.
Here what I know and what I have done:
The bias seems to increase on both channels just fine
The DC on left channel measures around 60mv at L21
The DC on right channel measures around 0.3v at L11
Q16,17,18,19 was swapped with working (?) channel
Emitter Q19 to Collector Q17 measures -28. other channel -38
R123 measure 0.3v
R115-116 where they meet also measure 0.3v
Not a single bad resistor! (I measured personally
)Already been fully recapped but problem persists..
Thats as far as mine and my friends (owner of Nad) ability goes to troubleshoot this..
Any help appreciated..
Attachments
The amber led at power up corresponds to the standby state, I assume nothing happens when you press the power button. If the amp was in protect the led would be red. Also need to be careful where you are checking dc offset, relay is not engagued so can't measure at spkr posts. Do you hear a relay click at "power on". Appears you have made comparisons with the other channel and found a difference and "assumed" this is the cause for protection. Check for excessive dc voltage by measuring at R150 (either side) or between R134, R135.
That 0.3V will be set by voltage/current at Q110 emitter
That 0.3V will be set by voltage/current at Q110 emitter
Hi, it doesn't power up. No relay clicks.
I did measure at R150 and found the probable cause which is high dc.
You think Q110 and or Q111 might be faulty? If so replacements will have to be ordered and they don't cheap cheap! 🙄
I did measure at R150 and found the probable cause which is high dc.
You think Q110 and or Q111 might be faulty? If so replacements will have to be ordered and they don't cheap cheap! 🙄
Check particularly the +/-18V rails
NAD C320BEE distortion
and then lots of small ish value electrolytic caps will need replacing near heat sources
NAD C320BEE distortion
and then lots of small ish value electrolytic caps will need replacing near heat sources
I will check rails but I believe they are OK.
I will have access after 7pm so I can do some tests.. Will report back findings. Thanks
I will have access after 7pm so I can do some tests.. Will report back findings. Thanks
"You mean I told you where the problem was" 
I laughed my head off thanks for that.
ALSO thank you because.......I had the exact same problem hahahaha
You just can't make this stuff up!!
Do you think it fried because of old caps?? I got sent a video of it measuring 40 mega ohms!!
I laughed my head off thanks for that.
ALSO thank you because.......I had the exact same problem hahahaha
You just can't make this stuff up!!
Do you think it fried because of old caps?? I got sent a video of it measuring 40 mega ohms!!
lol - well done 😉
Various small value caps will be fried 10uf, 22uf 47, 100 etc, check the colour for an indicator, most started out as the same colour
Various small value caps will be fried 10uf, 22uf 47, 100 etc, check the colour for an indicator, most started out as the same colour
Now you tell me LOL....
My mate just ordered 50 from China for £2 hahaha
And now the waiting game....🙁
My mate just ordered 50 from China for £2 hahaha
And now the waiting game....🙁
Well I fitted a carbon 0.5w 33r resistor and puff of smoke 🙁
I turned it off immediately, no fuses blown and it appears no other damage.
I had to leave it there and report what happened. We got the resistors on order but there clearly is some other issue.
I only had a chance to check for short around the resistor and nothing was shorted, I checked the adjacent transistors..
Any suggestions please?
MikePP you were right the amplifier was not even on! Orange was standby and as soon as I pressed CD, it went red and started the resistor smoked immediately..
I turned it off immediately, no fuses blown and it appears no other damage.
I had to leave it there and report what happened. We got the resistors on order but there clearly is some other issue.
I only had a chance to check for short around the resistor and nothing was shorted, I checked the adjacent transistors..
Any suggestions please?
MikePP you were right the amplifier was not even on! Orange was standby and as soon as I pressed CD, it went red and started the resistor smoked immediately..
In the other thread I did say the associated series pass transistor can fail , or the two smaller ones
It might not show up as short unless you monitor either the psu in or 18v out
Just get the transistor out of the board and check it Q41, Q42 (depending which rail ) or Q44/43 and don't forget the 47uf caps, I've had the 680r's fail too in other NAD's
It might not show up as short unless you monitor either the psu in or 18v out
Just get the transistor out of the board and check it Q41, Q42 (depending which rail ) or Q44/43 and don't forget the 47uf caps, I've had the 680r's fail too in other NAD's
Attachments
Fusible resistors a lot powerfull than normal ones. I don't know this is really true. But, I used taking risk 2watts for 1/2 watt.
Second, zener diot D49 may be wrong. Test or change it.
Second, zener diot D49 may be wrong. Test or change it.
Funny you mentioned that. Thats the only one that gave me values in both direction...
normal was 0.7 and revered was 1.0...I actually pulled that one diode out from one leg and measured and it measured 0.7 and only in the correct direction. I assumed it was fine!
normal was 0.7 and revered was 1.0...I actually pulled that one diode out from one leg and measured and it measured 0.7 and only in the correct direction. I assumed it was fine!