Arduino Nano PI Main Discussion

[MATT]

You say it looks good until you plug in the '5534. Have you tried a different opamp?

Thanks, yes that was one of the first things I tried before my original post.

[Qiaozhi]

You say it looks good until you plug in the '5534. Have you tried a different opamp?

I thought Matt had already tried a different NE5534, but now when I look back over the thread I can see that may not be the case.
However, the -5V supply doesn't drop when the 7660 is free-running.
It would definitely be worth trying a different opamp though.

[Carl-NC]

You say it looks good until you plug in the '5534. Have you tried a different opamp?

[MATT]

Sounds like a loading problem. Wrong cap values?

Thanks, I have double-checked all my caps but I will go through them again, I am a novice at this so your help is appreciated.

[MATT]

That would be my next step.
In the meantime you could continue building the rest of the detector with the 7660 in free-running mode.

Ok thanks for your help so far, I'll report back findings.

[Carl-NC]

Sounds like a loading problem. Wrong cap values?

[Qiaozhi]

Tried a 1k resistor at R1 and no change I'm afraid. Probably best to source some different manufacturers 7660's, do you think?

That would be my next step.
In the meantime you could continue building the rest of the detector with the 7660 in free-running mode.

[MATT]

It's must be a problem with the 7660 because your scope image (with R1 in-circuit) is the same as I see here.
Referring to the datasheet for the 7660, on page 8 it shows a series resistor of 1k, but I've never had a problem using 10K. It might be worth a try to reduce the value of R1 and see what happens.
Certainly no-one else has ever reported seeing this problem.

Tried a 1k resistor at R1 and no change I'm afraid. Probably best to source some different manufacturers 7660's, do you think?

[Qiaozhi]

Here is U2 Pin7 with R1 removed [ATTACH]57752[/ATTACH].
Here is U2 Pin7 with R1 in-circuit [ATTACH]57753[/ATTACH]

Thanks again for you continued help with this.

It's must be a problem with the 7660 because your scope image (with R1 in-circuit) is the same as I see here.
Referring to the datasheet for the 7660, on page 8 it shows a series resistor of 1k, but I've never had a problem using 10K. It might be worth a try to reduce the value of R1 and see what happens.
Certainly no-one else has ever reported seeing this problem.

[MATT]

This is very strange. I have double-checked the sync signal at TP2 on my own ANPI, and it looks exactly the same as your scope image.
The voltage at TP3 measures as -4.7V.
There still seems to be something amiss with the 7660, as it should be working with the sync signal applied.
Can you post a scope image of the signal on pin 7 of U2 (7660) with R1 in-circuit?

The detector will work if the voltage converter is free-running, but (as it says on page 10): "If the voltage converter was allowed to free-run (that is, use its own internal oscillator) switching transients could potentially affect the receive signal".

Here is U2 Pin7 with R1 removed .
Here is U2 Pin7 with R1 in-circuit

Thanks again for you continued help with this.

[Qiaozhi]

Thankyou, here are my results:
I bought the 7660 from RS Components. https://docs.rs-online.com/8c75/0900766b814f3c41.pdf
1. With the circuit on and before plugging in the NE5534 I get -4.63V, as I plug it in it drops to -2.38V
2. I've removed R1 and all now seems to be working and I get -4.79V

I've run all the other tests up to and including Main Sample, EFE Sample and Audio Chopper and all looks great Thanks very much for all your help so far. Should I keep building and testing without R1?

This is very strange. I have double-checked the sync signal at TP2 on my own ANPI, and it looks exactly the same as your scope image.
The voltage at TP3 measures as -4.7V.
There still seems to be something amiss with the 7660, as it should be working with the sync signal applied.
Can you post a scope image of the signal on pin 7 of U2 (7660) with R1 in-circuit?

The detector will work if the voltage converter is free-running, but (as it says on page 10): "If the voltage converter was allowed to free-run (that is, use its own internal oscillator) switching transients could potentially affect the receive signal".

[MATT]

Thanks for posting the details.
I cannot see anything wrong with the scope image or the PCB.
Where did you buy the 7660 ICs from? The symptoms still point to the voltage converter being a problem.

Here's a couple more things to try:
1. Plug the NE5534 into the socket with the circuit running, and see if the power supply still drops to -2.5V.
2. Remove R1 and see if the 7660 will free-run.

Thankyou, here are my results:
I bought the 7660 from RS Components. https://docs.rs-online.com/8c75/0900766b814f3c41.pdf
1. With the circuit on and before plugging in the NE5534 I get -4.63V, as I plug it in it drops to -2.38V
2. I've removed R1 and all now seems to be working and I get -4.79V

I've run all the other tests up to and including Main Sample, EFE Sample and Audio Chopper and all looks great Thanks very much for all your help so far. Should I keep building and testing without R1?

[Qiaozhi]

Hi, thanks for coming back to me:
1. Yes I have examined with an oscilloscope, output here [ATTACH]57751[/ATTACH]
2. [ATTACH]57750[/ATTACH]

Thanks for posting the details.
I cannot see anything wrong with the scope image or the PCB.
Where did you buy the 7660 ICs from? The symptoms still point to the voltage converter being a problem.

Here's a couple more things to try:
1. Plug the NE5534 into the socket with the circuit running, and see if the power supply still drops to -2.5V.
2. Remove R1 and see if the 7660 will free-run.

[MATT]

Two things:
1. Have you examined the signal at TP2 with an oscilloscope?
2. Can you post a clear photo of the PCB?

Hi, thanks for coming back to me:
1. Yes I have examined with an oscilloscope, output here
2.

[Qiaozhi]

Thanks for your guidance. I have swapped out the 7660 and no change I'm afraid. I've also checked TP2 and pin 7 on the 7660 and both are 1.01Khz. Any further thoughts?

Two things:
1. Have you examined the signal at TP2 with an oscilloscope?
2. Can you post a clear photo of the PCB?