Nad c 355 bee integrated amplifier light?

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kuer

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Joined 2014
Hi, a NAD 355bee amplifier, the small blue led light for the tuner selection on the face plate was burnt out, but works good, other lights are good. Contacted the nad, they are really expensive.

Wondering if anybody will kindly provide the model of the led? I can't upload the whole service manual, please download from the following link and check out.

NAD C355BEE Manual - Stereo Integrated Amplifier - HiFi Engine

I read the service manual, should be somewhere, but didn't find out the model, maybe I am not familiar with the diagram.

Thank you very much.
 
Bill_P

Bill_P

Member
Joined 2009
From service manual pages 18a and 18b there was a change to blue LEDs in later production. The parts list only shows the older green LEDs. Have you measured the voltage across the Tuner LED when that input is selected? If 3 volts or more is present then the LED is bad or has a bad solder joint. It looks like the LED normally runs on 7.5 mA forward current. You can measure the voltage across R727 to determine the current.
 
K

kuer

Member
Joined 2014
Bill_P said:
From service manual pages 18a and 18b there was a change to blue LEDs in later production. The parts list only shows the older green LEDs. Have you measured the voltage across the Tuner LED when that input is selected? If 3 volts or more is present then the LED is bad or has a bad solder joint. It looks like the LED normally runs on 7.5 mA forward current. You can measure the voltage across R727 to determine the current.
Click to expand...

Not even opened. will measure later. Thank you.
 
K

kuer

Member
Joined 2014
Bill_P said:
From service manual pages 18a and 18b there was a change to blue LEDs in later production. The parts list only shows the older green LEDs. Have you measured the voltage across the Tuner LED when that input is selected? If 3 volts or more is present then the LED is bad or has a bad solder joint. It looks like the LED normally runs on 7.5 mA forward current. You can measure the voltage across R727 to determine the current.
Click to expand...

A little weird, checked them. this non-working led is at 9v 10ma when off, while it is 12v 10ma when on (selected), 3v difference.

but all other working lights are 3v 10ma when on, 0v when off, 3v difference. All lights look the same model, no difference.
 
Bill_P

Bill_P

Member
Joined 2009
R727 feeds six LEDs so there can be some interaction in the measurement. Are you measuring to ground or across the LED? If the CD, Aux, Video etc. LEDs work normally then R727 is working normally. Only two components can affect the Tuner light then - the LED itself and transistor Q712 along with its base resistors. When you select Tuner, does Q712 turn on? Measure base to emitter and collector to emitter voltages. If Q712 doesn't turn on when Tuner is activated then the LED might be good and the transistor bad.
 
K

kuer

Member
Joined 2014
Bill_P said:
R727 feeds six LEDs so there can be some interaction in the measurement. Are you measuring to ground or across the LED? If the CD, Aux, Video etc. LEDs work normally then R727 is working normally. Only two components can affect the Tuner light then - the LED itself and transistor Q712 along with its base resistors. When you select Tuner, does Q712 turn on? Measure base to emitter and collector to emitter voltages. If Q712 doesn't turn on when Tuner is activated then the LED might be good and the transistor bad.
Click to expand...

Everything works good, not measure the ground. I will get a led to tried it out, if good, good. Thanks.
 
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