Hi
I think I'm going crazy. I cannot figure out how I can make my amp get out of protection mode. I have attached the schematics for the psu. I hope someone will be able to help me (my girlfriend would be happy too, because a NAD319 can take up a lot of space, when disassembled)
To my understanding, the TA7317 chip drags PIN 6 to ground (PIN 4), when PIN 1 is less than 0.7V, PIN 2-3 are 0V and PIN 8 are >~ 2*0.7. Is that correct?
In the schematics NAD states that the voltages around the TA7317 should be:
P1: 0.3
P2-4: 0
P5: -0.77
P6: 0 (relay turned on)
P8: 1.3
P9: 3.13
When I measure the voltages in my amp I get:
P1: 0.120
P2-4: ~0 (0.x mV)
P5: -0.77
P6: 64 (relay turned off)
P8: 50mV
P9: 3.13
I have tried to replace most of the capacitors and I have not been able to find shorts or opens or anything like that. When I remove the cap (C224) on PIN8 the relay starts oscillating (switching on and off), but with a frequency greater than 1Hz. If I remove cap C223 on PIN 7, the frequency gets even higher. If I re-insert C224, the oscillations stops, but it stays in protect mode.
I have tried to replace the TA7317, but that didn't help.
Does anyone have an idea on how to fix this? Or just some hints on what I should investigate further.
Not sure if the attach worked:
Nad 319 psu schematics
/Christian
I think I'm going crazy. I cannot figure out how I can make my amp get out of protection mode. I have attached the schematics for the psu. I hope someone will be able to help me (my girlfriend would be happy too, because a NAD319 can take up a lot of space, when disassembled)
To my understanding, the TA7317 chip drags PIN 6 to ground (PIN 4), when PIN 1 is less than 0.7V, PIN 2-3 are 0V and PIN 8 are >~ 2*0.7. Is that correct?
In the schematics NAD states that the voltages around the TA7317 should be:
P1: 0.3
P2-4: 0
P5: -0.77
P6: 0 (relay turned on)
P8: 1.3
P9: 3.13
When I measure the voltages in my amp I get:
P1: 0.120
P2-4: ~0 (0.x mV)
P5: -0.77
P6: 64 (relay turned off)
P8: 50mV
P9: 3.13
I have tried to replace most of the capacitors and I have not been able to find shorts or opens or anything like that. When I remove the cap (C224) on PIN8 the relay starts oscillating (switching on and off), but with a frequency greater than 1Hz. If I remove cap C223 on PIN 7, the frequency gets even higher. If I re-insert C224, the oscillations stops, but it stays in protect mode.
I have tried to replace the TA7317, but that didn't help.
Does anyone have an idea on how to fix this? Or just some hints on what I should investigate further.
Not sure if the attach worked:
Nad 319 psu schematics
/Christian
I have the datasheet already.
TA7317P datasheet
I have tried to simulate it in spice, but it worked nicely and I couldn't make it oscillate. I'm beginning to think that the low voltage on PIN 8 is not the problem itself, but rather a consequence of another failure in the circuit.
TA7317P datasheet
I have tried to simulate it in spice, but it worked nicely and I couldn't make it oscillate. I'm beginning to think that the low voltage on PIN 8 is not the problem itself, but rather a consequence of another failure in the circuit.
The circuit is being externally muted because pin 8 of the IC is not being pulled up. Check R233 (open) and C224 (shorted or leaky).
You may try to inject a very small current into pin 8 by connecting a very high value resistor (500k to 1 Meg) to one of the positive 60V rails. If C224 is not shorted, this should cause the relay to turn on (you may cause damage if the current is too high).
You may try to inject a very small current into pin 8 by connecting a very high value resistor (500k to 1 Meg) to one of the positive 60V rails. If C224 is not shorted, this should cause the relay to turn on (you may cause damage if the current is too high).
Progress
Thanks eva! It wasn't the problem, but just some fresh thinking made me approach the problem differently.
I think I'm quite close to the solution now. I have discovered that it's the voltage on p1 that mutes the system. I have tried to short it to ground (through my meter) several times, but then I suddenly realized that the time constant of the muting circuit is much larger than just a simple touch, so I was patient and after 2-3 seconds, the amp went out of protect. Now I just have to figure out why pin 1 is not tied to ground.
Thanks eva! It wasn't the problem, but just some fresh thinking made me approach the problem differently.
I think I'm quite close to the solution now. I have discovered that it's the voltage on p1 that mutes the system. I have tried to short it to ground (through my meter) several times, but then I suddenly realized that the time constant of the muting circuit is much larger than just a simple touch, so I was patient and after 2-3 seconds, the amp went out of protect. Now I just have to figure out why pin 1 is not tied to ground.
Problem solved!!!!
I finally found the broken component. It was a simple 1N4148 diode (D211) that was shorted. I'm not sure what I will do with that diode, but it'll have to suffer somehow. Maybe I should smash it with a big hammer. >
I have spend so much time on this amp that I could have made a complete diy power amp. I even made a new pcb for the psu - no silk screen, but I bet the quality is better than the original.
I finally found the broken component. It was a simple 1N4148 diode (D211) that was shorted. I'm not sure what I will do with that diode, but it'll have to suffer somehow. Maybe I should smash it with a big hammer. >
I have spend so much time on this amp that I could have made a complete diy power amp. I even made a new pcb for the psu - no silk screen, but I bet the quality is better than the original.
Idle current
Now that its working and disasembled, I might as well adjust the idle current. The output is four pairs of 2SC3519/2SA1386 connected through 0.22 Ohm resistors to the speaker. The two measure pins are connected between the transistor and resistor on one of the pairs.
I can adjust the voltage from 0V to approx 10mV. What should it be?
I have the schematics, but it doesn't say what it should be adjusted to. Is it a tradeof between power consumption and crossover distortion?
Now that its working and disasembled, I might as well adjust the idle current. The output is four pairs of 2SC3519/2SA1386 connected through 0.22 Ohm resistors to the speaker. The two measure pins are connected between the transistor and resistor on one of the pairs.
I can adjust the voltage from 0V to approx 10mV. What should it be?
I have the schematics, but it doesn't say what it should be adjusted to. Is it a tradeof between power consumption and crossover distortion?
My NAD 319 voltages
Hi Cviller,
Here are my TA 7317 voltages:
1. 0.3
2. 0
3. 0
4. 0
5 -0.7
6. 0
7. 0
8. 1.3
9. 3
Around my D211 diode I am reading around -29V rather than the supposed around 60V.
Can you also answer the following:
1.What does the relay of teh protection circuit actually control? (does it control teh speaker outputs or does it prevent an input into the main power amp boards?)
2.From th eoutput of Pin 6 of TA7317, where does that signal go (it goes to J107 but what next?)
3.Where does the J108 pin 2 connect to? It is connected to the Thermal Resistor (?) THR1?
Hi Cviller,
Here are my TA 7317 voltages:
1. 0.3
2. 0
3. 0
4. 0
5 -0.7
6. 0
7. 0
8. 1.3
9. 3
Around my D211 diode I am reading around -29V rather than the supposed around 60V.
Can you also answer the following:
1.What does the relay of teh protection circuit actually control? (does it control teh speaker outputs or does it prevent an input into the main power amp boards?)
2.From th eoutput of Pin 6 of TA7317, where does that signal go (it goes to J107 but what next?)
3.Where does the J108 pin 2 connect to? It is connected to the Thermal Resistor (?) THR1?
Re: My NAD 319 voltages
Protection relays typically provide a way to decouple the output of the amp from the speakers at power up and power down to prevent transients from reaching the speakers, and also a way to disconnect the speakers in the event the circuitry detects a fault with the amplifier.twofake said:
Thanks EchoWars. I suspected that once I get the protection relay to close that the amp will work again. Currently it remains open (with no clicking after the set protection time elapses).
I tested the power amp section to the best of my ability and think that that section (right and left channels) is fine.
I tested the power amp section to the best of my ability and think that that section (right and left channels) is fine.
Re: My NAD 319 voltages
Replace it. If I remember correctly, this was actually the damn component which prevented me from getting the circuit to work.
it goes through the supply boards and some thermal protections - you should measure if there is a correct low ohm path from ic202 p6 to j108 p2 or the point between r228 and r228.
yes
twofake said:
Replace it. If I remember correctly, this was actually the damn component which prevented me from getting the circuit to work.
it goes through the supply boards and some thermal protections - you should measure if there is a correct low ohm path from ic202 p6 to j108 p2 or the point between r228 and r228.
[/B][/QUOTE]
yes
Replace it. If I remember correctly, this was actually the damn component which prevented me from getting the circuit to work."
Thanks again Cviller,
Not knowing a lot about how this diode affects the circuit, can you tell me what could cause this same component (as your amp) to fail and if its failure could affect the voltage so much?
From your advice, I will desolder it and test the component and replace it. I will let you know the result when I have completed the tasks.
Thanks again Cviller,
Not knowing a lot about how this diode affects the circuit, can you tell me what could cause this same component (as your amp) to fail and if its failure could affect the voltage so much?
From your advice, I will desolder it and test the component and replace it. I will let you know the result when I have completed the tasks.
Diode 211 replaced
I have removed and tested the D211 which was in short circuit. The protection is still on. Voltage either side of R252 is still around -29 volts. Voltage either side of R210 is Zero. Voltage between D206 and C206 is 51V and btween R203 to D206 is 101.7V.
If D211 goes short curcuit, which component along the line is likely to blow next?
I have removed and tested the D211 which was in short circuit. The protection is still on. Voltage either side of R252 is still around -29 volts. Voltage either side of R210 is Zero. Voltage between D206 and C206 is 51V and btween R203 to D206 is 101.7V.
If D211 goes short curcuit, which component along the line is likely to blow next?
Have you checked the connection from p6 on the ta7317 chip all the way to the relay coil?
Your main capacitors may have dried out - do you have a scope?
I don't think the d211 will take anything along with it, it is a normal small diode - although you could check c226.
Btw: do you have everything connected or are you only testing the psu board?
Your main capacitors may have dried out - do you have a scope?
I don't think the d211 will take anything along with it, it is a normal small diode - although you could check c226.
Btw: do you have everything connected or are you only testing the psu board?
Have you checked the connection from p6 on the ta7317 chip all the way to the relay coil?
Yes I just checked it and it is all fine
Your main capacitors may have dried out - do you have a scope?
I do have a scope.Let me know what tests you wnat me to do. I have a function generator and I also have an ESR meter that I made to check capacitors and I think that C226 is OK.
I don't think the d211 will take anything along with it, it is a normal small diode - although you could check c226.
[Thanks.That makes me feel better.
Btw: do you have everything connected or are you only testing the psu board?
My engineer friend suggested I remove the power amp boards for safety but also I was having a lot of problems getting underneath the main board because of the way they are all aired together. I now realise that the thermal resistors which I assume have zero (or close to it) resistance when not overheated, would not have been connected and may have affected the ta7317 chip. Tnight, I have replaced the absolutely terrible (matches the absolutely terrible PCB!!) audio wires joining the main PSU boards to the seperate power amp boars. I have wired in connectors (obtained from old VCR) so that I can palce the boards and then clip them together. the connectors also have the advantage that I can quickly check that there are no short circuits where the solder joints are. Tomorrow I'll see if I can find lareg connectors to wire the 4 power wires onto each board and thenI'll do soem more tests. Stay posted.
Yes I just checked it and it is all fine
Your main capacitors may have dried out - do you have a scope?
I do have a scope.Let me know what tests you wnat me to do. I have a function generator and I also have an ESR meter that I made to check capacitors and I think that C226 is OK.
I don't think the d211 will take anything along with it, it is a normal small diode - although you could check c226.
[Thanks.That makes me feel better.
Btw: do you have everything connected or are you only testing the psu board?
My engineer friend suggested I remove the power amp boards for safety but also I was having a lot of problems getting underneath the main board because of the way they are all aired together. I now realise that the thermal resistors which I assume have zero (or close to it) resistance when not overheated, would not have been connected and may have affected the ta7317 chip. Tnight, I have replaced the absolutely terrible (matches the absolutely terrible PCB!!) audio wires joining the main PSU boards to the seperate power amp boars. I have wired in connectors (obtained from old VCR) so that I can palce the boards and then clip them together. the connectors also have the advantage that I can quickly check that there are no short circuits where the solder joints are. Tomorrow I'll see if I can find lareg connectors to wire the 4 power wires onto each board and thenI'll do soem more tests. Stay posted.
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