Hello.
Integrated amplifier NAD C352.
In Protect mode.
All 4 fuses are OK
Where I need control please.
SM
NAD C 352 Service Manual
Integrated amplifier NAD C352.
In Protect mode.
All 4 fuses are OK
Where I need control please.
SM
NAD C 352 Service Manual
check the values of R153, R155, R154, R156, they should be 82 ohm, 1W.
check R113, R115, R114, R116. 10ohm.
check the values of C119. C121, c120, C122, they should be 220u/63v, its better change all of them.
also check C107, C109, C108, C120. 10u/50v. better change them all.
VR101, VR102, 100ohm, look like that can help fine tune the output to 0v.
As its been a long time, resistors could change their values overtime sometimes even open,
capacitors dry up or lost their functions. Its best to check them one by one.
It takes time but worthy.
check the diodes, check all other components on the board, dry joints, bad joints, damaged pads etc.
There's no short way to fix it, you have to take time and patience.
check R113, R115, R114, R116. 10ohm.
check the values of C119. C121, c120, C122, they should be 220u/63v, its better change all of them.
also check C107, C109, C108, C120. 10u/50v. better change them all.
VR101, VR102, 100ohm, look like that can help fine tune the output to 0v.
As its been a long time, resistors could change their values overtime sometimes even open,
capacitors dry up or lost their functions. Its best to check them one by one.
It takes time but worthy.
check the diodes, check all other components on the board, dry joints, bad joints, damaged pads etc.
There's no short way to fix it, you have to take time and patience.
1 "with phone jack in, no protect mode" so you can hear music with the phone, right?
If there were no protect mode, that means speakers are connected to the amps and
music should be heard then, can you hear the music with the speakers?
2 with phone jack in, can you hear the speaker relay click ?
( from the schematic I see a switch built in the jack when phone inserted in, it will cut the power of the relay. so the relay shouldn't click- is this right )
3 0.5v at output should trigger protection mode. check all voltages.
4 check the supply rail of the op amps TL082.
5 sorry for the VRs. I have amps use it to adjust the output to 0v. this amp use op amp.
6 You work very fast, Sometimes after fixing the amps, find it only a silly problem.
just like fixing the dry joints now lower the output voltages to 0.5v
7 It needs a thorough check, good luck.
If there were no protect mode, that means speakers are connected to the amps and
music should be heard then, can you hear the music with the speakers?
2 with phone jack in, can you hear the speaker relay click ?
( from the schematic I see a switch built in the jack when phone inserted in, it will cut the power of the relay. so the relay shouldn't click- is this right )
3 0.5v at output should trigger protection mode. check all voltages.
4 check the supply rail of the op amps TL082.
5 sorry for the VRs. I have amps use it to adjust the output to 0v. this amp use op amp.
6 You work very fast, Sometimes after fixing the amps, find it only a silly problem.
just like fixing the dry joints now lower the output voltages to 0.5v
7 It needs a thorough check, good luck.
it takes a long time for me to check the components.
do you mind telling me how you did it.
please in details how you check resistors, capacitors, transistors etc,.it matters.
this amp needs a thorough check on every part.
all voltages must be same value as the schematic stated so are the quality of the components..
do you mind telling me how you did it.
please in details how you check resistors, capacitors, transistors etc,.it matters.
this amp needs a thorough check on every part.
all voltages must be same value as the schematic stated so are the quality of the components..
VR101 and VR102 set the bias current in the input stage. They don't control offset.
The offset is set by a DC servo (IC107A, IC108A). Measure the DC output voltage of those servos. That'd be pin 1 of the TL082 ICs. They should be reasonably low. A few volt maybe. If they're close to the supply rail (measure pins 4, 8) either a) you have excessive DC offset on the input of the power amp section or b) the IC is toast.
Measure the DC voltage at each end of R111 and R112. They should be pretty close to zero. Certainly below 1 V would be my expectation.
Tom
Excellent!
again from your brief answer I can't figure out how you did it.
do you mind up load the photos of the inside of the amp and your 'parts checker'.
when all components are checked in good condition and properly soldered together, the amp should work perfectly. but there is 0.5v at the output. what caused it then?
here's a ref with the same issue, may be helpful to you.
Last month I bought a vintage Pioneer A70 which use op amp like yours.
the output offset was higher than 3v.
after a thorough check I found the power rail for that IC was abnormal.
it was the resistors in the rails had changed their values, one can't tell from their outside look that's defective. So I changed them to 1w instead of 1/2w. and changed the bypass capacitors too. it went back to normal.
again from your brief answer I can't figure out how you did it.
do you mind up load the photos of the inside of the amp and your 'parts checker'.
when all components are checked in good condition and properly soldered together, the amp should work perfectly. but there is 0.5v at the output. what caused it then?
here's a ref with the same issue, may be helpful to you.
Last month I bought a vintage Pioneer A70 which use op amp like yours.
the output offset was higher than 3v.
after a thorough check I found the power rail for that IC was abnormal.
it was the resistors in the rails had changed their values, one can't tell from their outside look that's defective. So I changed them to 1w instead of 1/2w. and changed the bypass capacitors too. it went back to normal.
Read the schematic and follow it carefully
I found on page 2, I was right.
the output offset is control by VR101 Left channel, VR102 R channel.
ALIGNMENT PROCEDURE (C352)
I. INITIAL ADJUSTMENT (No load connected)
A. OUTPUT OFFSET VOLTAGE
1. Connect a DC Millivoltmeter to L Channel speaker output terminals.
2. Turn unit “ON” and adjust VR101 (100ohms) to get a reading on IC107 Pin 1,
which must be <100mV.
3. Connect the DC Millivoltmeter to R Channel speaker output terminals and adjust
VR102 (100ohms) to get a reading on IC108 Pin 1, which must be <100mV.
now you know the voltages on pin1 of IC107 and IC108.
B. IDLING CURRENT
1. Leave power “ON” for a minimum of 5 minutes.
2. Connect a DC Millivoltmeter to TP101 and TP102, then adjust VR103 (300ohms)
for 5-6.5mV reading on meter.
3. Connect a DC Millivoltmeter to TP103 and TP104, then adjust VR104 (300ohms)
for 5-6.5mV reading on meter.
You may fix the problem after you go through the schematic with heart.
compare the voltages with the schematic.
sorry can't help cause don't understand your brief questions.
I found on page 2, I was right.
the output offset is control by VR101 Left channel, VR102 R channel.
ALIGNMENT PROCEDURE (C352)
I. INITIAL ADJUSTMENT (No load connected)
A. OUTPUT OFFSET VOLTAGE
1. Connect a DC Millivoltmeter to L Channel speaker output terminals.
2. Turn unit “ON” and adjust VR101 (100ohms) to get a reading on IC107 Pin 1,
which must be <100mV.
3. Connect the DC Millivoltmeter to R Channel speaker output terminals and adjust
VR102 (100ohms) to get a reading on IC108 Pin 1, which must be <100mV.
now you know the voltages on pin1 of IC107 and IC108.
B. IDLING CURRENT
1. Leave power “ON” for a minimum of 5 minutes.
2. Connect a DC Millivoltmeter to TP101 and TP102, then adjust VR103 (300ohms)
for 5-6.5mV reading on meter.
3. Connect a DC Millivoltmeter to TP103 and TP104, then adjust VR104 (300ohms)
for 5-6.5mV reading on meter.
You may fix the problem after you go through the schematic with heart.
compare the voltages with the schematic.
sorry can't help cause don't understand your brief questions.