I can’t see another path for pin 6. It just ends there. The ”arc” is from my soldering/ solder wick.
It can not work as it is 🙂 Try and trace the Zener and see where that goes. Does it go to that empty pad?
Check and try and confirm/prove everything I say because I'm not infallible 🙂 Without the connection to pin 6 I do not see any way the relay transistor can be driven.
Check and try and confirm/prove everything I say because I'm not infallible 🙂 Without the connection to pin 6 I do not see any way the relay transistor can be driven.
It's not easy working from pictures I'm afraid. I can't easily decipher much from that tbh.
That looks a different board anyway... is that just off the web? I can see pin 6 is isolated on that one as well which if so I agree is very very odd indeed.
I know my theory is good on this 🙂 and that as drawn in the circuit diagram the line marked PT-OUT must go low. Pin 6 performs that function.
If pin 6 is left open then all that circuitry does nothing. The DC offset inputs, the overcurrent inputs, AC detection and so on. All these feed into the module and the module operates the two relays in response to the correct conditions being met. Does that make some kind of sense?
I can't really suggest anything else to you at this stage because I have to work from the published circuit.
That looks a different board anyway... is that just off the web? I can see pin 6 is isolated on that one as well which if so I agree is very very odd indeed.
I know my theory is good on this 🙂 and that as drawn in the circuit diagram the line marked PT-OUT must go low. Pin 6 performs that function.
If pin 6 is left open then all that circuitry does nothing. The DC offset inputs, the overcurrent inputs, AC detection and so on. All these feed into the module and the module operates the two relays in response to the correct conditions being met. Does that make some kind of sense?
I can't really suggest anything else to you at this stage because I have to work from the published circuit.
Attachments
Yes it is D718, thats ”Z” i made in the upper picture. An now those pics i’ve taken myself
I can check for continuity tomorrow. (Should have done that already but been busy with other things)
I can check for continuity tomorrow. (Should have done that already but been busy with other things)
Old pic but only i had to show the jumper... found a jumper to that pad (i think) will check more soon! That connects non ring side with a 5.6k (R767) but in between the jumper goes down to pin 6 but really the other side on the pad it looks kinda flat.. hmm have to check that really closely
Attachments
Yes, prove by continuity checks and visual inspection and see where the junction of the Zener and the 5k6 go.
The circuit clearly shows they go to pin 6. I looked at the chip data sheet (the manufactures sheet, not NAD's) as well and the pin outs match for the chip and discrete module match as they should.
The circuit clearly shows they go to pin 6. I looked at the chip data sheet (the manufactures sheet, not NAD's) as well and the pin outs match for the chip and discrete module match as they should.
Yes there is a jumper going from that ”pad” over to junction 5.6k and 10v zener. Just checked it
So does pin 6 of the module have direct continuity to the Zener? That's what I need to know.
Yes or no 🙂 Everything hinges on that.
Yes or no 🙂 Everything hinges on that.
Good 🙂
So next step is to see exactly what the speaker relays are doing.
If you connect your meter across diode D713 (that is the diode across the relay coils) we can look at the voltage and get an idea of what is going on.
(There might be some other small signal muting of the audio buried within the circuit but lets get the basics sorted first)
So as you power the amp up I would expect to see the voltage across the relay coils come up to say 25 to 30 volts or so after a delay of 2 to 3 seconds.
Exact voltage depends on the resistance of the coils and the current they draw which in turn will cause a volt drop across R766. The relay voltage may well be marked on the relay itself.
So get an idea of the voltage and the time delay and then try switching off and on and see what the delay in coil voltage appearing is then. I would expect it to be a constant delay but lets see and put some numbers in.
So next step is to see exactly what the speaker relays are doing.
If you connect your meter across diode D713 (that is the diode across the relay coils) we can look at the voltage and get an idea of what is going on.
(There might be some other small signal muting of the audio buried within the circuit but lets get the basics sorted first)
So as you power the amp up I would expect to see the voltage across the relay coils come up to say 25 to 30 volts or so after a delay of 2 to 3 seconds.
Exact voltage depends on the resistance of the coils and the current they draw which in turn will cause a volt drop across R766. The relay voltage may well be marked on the relay itself.
So get an idea of the voltage and the time delay and then try switching off and on and see what the delay in coil voltage appearing is then. I would expect it to be a constant delay but lets see and put some numbers in.
The old relays had a res of 3.2k while the new ones are 2.4k. Voltage of relays are 36v it says (2x Omron Gr2-1Ae 36vdc)
Originals was chinese and one of them worked poorly.
First things i threw in and it worked good so i didn’t bother to adjust anything. Voltage i measured before. Relays see 32.75v i think
Will check voltade over that D713 too. But i don’t have 2-3 sec delay?��
Originals was chinese and one of them worked poorly.
First things i threw in and it worked good so i didn’t bother to adjust anything. Voltage i measured before. Relays see 32.75v i think
Will check voltade over that D713 too. But i don’t have 2-3 sec delay?��
The relays should see around 28 volts (very approx) if they have 2k4 coils and the main supply is +34V. The 6 volt drop is down to the relay current causing a drop across the 220 ohm limiter resistor R766.
Anyhow... just like with pin 6 we need to be 100% sure what is happening and that means measuring the coil voltage and in particular looking at the delay you see.
There a couple of possibilities for the way all this works and so we need measurements to clarify how it all operates as one unit.
1/ When you power up from a cold start (all off, everything discharged) what delay do see by measuring the voltage across the relay coils?
2/ If you remove power (unplug from mains) for a few seconds and then repeat the above step what delay do you now see?
What we are going to look at here (if there is a difference) is what has changed around the module. The delay should be repeatable.
Now look at the circuit and find D701 which is across the power standby relay coil.
When you initially plug the unit in to the mains does this coil get 5V across it or does it not energise until you take it out of standby.
What we are trying to determine here is whether the standby function switches this relay on and off correctly and how that relates to the modules delay time. The module is fed from a 34V rail that is derived from a supply off the large transformer and so the module should give a repeatable delay each time the power relay is cycled on and off.
(a random thought... is it possible you blobbed any solder onto the module during the recap?)
Anyhow... just like with pin 6 we need to be 100% sure what is happening and that means measuring the coil voltage and in particular looking at the delay you see.
There a couple of possibilities for the way all this works and so we need measurements to clarify how it all operates as one unit.
1/ When you power up from a cold start (all off, everything discharged) what delay do see by measuring the voltage across the relay coils?
2/ If you remove power (unplug from mains) for a few seconds and then repeat the above step what delay do you now see?
What we are going to look at here (if there is a difference) is what has changed around the module. The delay should be repeatable.
Now look at the circuit and find D701 which is across the power standby relay coil.
When you initially plug the unit in to the mains does this coil get 5V across it or does it not energise until you take it out of standby.
What we are trying to determine here is whether the standby function switches this relay on and off correctly and how that relates to the modules delay time. The module is fed from a 34V rail that is derived from a supply off the large transformer and so the module should give a repeatable delay each time the power relay is cycled on and off.
(a random thought... is it possible you blobbed any solder onto the module during the recap?)
I checked when its in standby the D718 have contantly 1.5v over it and i have -1.5v at pin 4
Edit: When in standby also main filtercaps have 1.9v constantly over them.
And the now famous 47uf has 1.19v across it.
As soon as i pull the power it discharges in a min or two.
Hmmm this can’t be normal
Edit: When in standby also main filtercaps have 1.9v constantly over them.
And the now famous 47uf has 1.19v across it.
As soon as i pull the power it discharges in a min or two.
Hmmm this can’t be normal
Last edited:
The residual voltages are probably normal tbh. Once the power is cut and the rails fall, a point will be reached where the circuitry suddenly starts drawing very little current and so so the reservoir caps seem to stop discharging at that point.
Have a read at post #74, the things I mentioned to check there might help give a clue.
Just for curiosity... and this is very interesting... I tried the simulation beginning with the rail voltage at 2V and and then switching it to 34V. The initial charge that the 47uF gains while the rail has a small residual voltage absolutely kills the delay time to about 0.7 seconds.
Here are the two charts. On the first the rail starts at zero and then comes up to 34 volts. On the second it starts at 2 volts before coming up to 34v.
You can see the difference in delay time very clearly.
The big big question though has to be WHY the recap has altered the behaviour. Did you stick to the original capacitance values?
Have a read at post #74, the things I mentioned to check there might help give a clue.
Just for curiosity... and this is very interesting... I tried the simulation beginning with the rail voltage at 2V and and then switching it to 34V. The initial charge that the 47uF gains while the rail has a small residual voltage absolutely kills the delay time to about 0.7 seconds.
Here are the two charts. On the first the rail starts at zero and then comes up to 34 volts. On the second it starts at 2 volts before coming up to 34v.
You can see the difference in delay time very clearly.
The big big question though has to be WHY the recap has altered the behaviour. Did you stick to the original capacitance values?
Attachments
Btw, R768 in curcuit says 10k but according to colourcode (and measuring) it is 3.9K.
Was thinking your simulation.
Anyway, yes i will measure more of what you said.
And yes i did use same values but some of them are higher voltage rating. Like some that was 25V is now, 35, 50 or 100V.
But i recall that some 10uf that was good measured 14-16uF.. while the bad ones was down.
The 330uf cap in that protection curcuit measured 365uf. So that one was ok i guess but i still thought while recapping rest should i really leave just one old? Asthetics i guess for me.
Was thinking your simulation.
Anyway, yes i will measure more of what you said.
And yes i did use same values but some of them are higher voltage rating. Like some that was 25V is now, 35, 50 or 100V.
But i recall that some 10uf that was good measured 14-16uF.. while the bad ones was down.
The 330uf cap in that protection curcuit measured 365uf. So that one was ok i guess but i still thought while recapping rest should i really leave just one old? Asthetics i guess for me.
Last edited:
Well spotted 🙂
That was something I was playing around with earlier to try and get a handle on why it wasn't working in simulation and never changed back.
This bit actually from post #60:
It is a current limiter for the Zener stabilised supply... now back at 10k. The sim result is unchanged because the Zener clamps the voltage.
Different voltage ratings won't make any difference, I was thinking more of values being increased in the belief bigger is better (as many do with reservoir and smoothing caps), however here the values are critical to ensure the rails all sequence correctly and have the correct rise and fall characteristics.
That was something I was playing around with earlier to try and get a handle on why it wasn't working in simulation and never changed back.
This bit actually from post #60:
It is a current limiter for the Zener stabilised supply... now back at 10k. The sim result is unchanged because the Zener clamps the voltage.
Different voltage ratings won't make any difference, I was thinking more of values being increased in the belief bigger is better (as many do with reservoir and smoothing caps), however here the values are critical to ensure the rails all sequence correctly and have the correct rise and fall characteristics.
All values are spot on regarding caps except main filter caps that are 6x8200uf.
Thinking (what i didn’t actually know) that electrolytic caps doesn’t behave good if full or nearly full voltage is’nt applied like some caps that been 16v rating are now maybe 35, 50
Or even 100v so ”worried” they’re not giving their full capacitance.
Something i should worry about?
I have problem to hold probes at the same time pushing power button and on top of that and now my delay is very consistent. My wife haveto help me i guess.. 🙂
Also discovered something else regarding that main power switch (or vacation Nad likes to refer to)
I attach a pic to show what i did. Back in my head somehow i think this relates to that Ato board and how it interacts with the process.
If i pull the cables circled with blu and then attach the powercord without touching anything else the amp will start up and relays will click on. Also the ”sense” led in front will shine. �� how the heck is that possible.
Tried to measure voltage from standby board but only reading i could get was +2.5v. Went through it and replaced the regulator, (7805) zener, well everything actually. Carefully checked everything. Same thing, same voltage. This is when connected to ato board.
On the ato board i saw a resistor that was wrong value, suppose to be 10k but it was 1k. (my mistake) This was R819. Now the delay is somewhat shorter. Perhaps0.3- 0.5 sec slower.
I have rechecked everything along this but nothing. Can somehow this big ic (74hc14?) be damaged from esd?) or the other 2 big ic’s?
On the older Nad c270 there is no ato or sense board but everything is thr same and there the 5v supply from standby board will go directly to main psu baord (aka protection curcuit) thinking trying to hook that 4-pin directly there but afraid i will screw something up.
Update: If i pull only the cable to sense board the standby relay will click. Also weird.
Will try to do more checking today and measuring.
Attachments
Last edited: