Arduino Nano PI Main Discussion

[MATT]

Hi I have built ANPI to the preamp stage but now I'm not getting -5v from TP3, I get circa -2.5v instead. When I remove the NE5534 I get -5v again. Could someone point me in the right direction? - I am a novice at this so any help would be appreciated?

[Qiaozhi]

Hi I have built ANPI to the preamp stage but now I'm not getting -5v from TP3, I get circa -2.5v instead. When I remove the NE5534 I get -5v again. Could someone point me in the right direction? - I am a novice at this so any help would be appreciated?

Are you building the ANPI on a PCB manufactured using the supplied Gerber files, or are you breadboarding the design?

[MATT]

I'm using the manufactured PCB I bought it from DiyDetector (used to be SilverDog I think)

[Qiaozhi]

I'm using the manufactured PCB I bought it from DiyDetector (used to be SilverDog I think)

That's good, as it eliminates possible wiring errors.
Have you tried swapping out the 7660?
Also, I presume the 7660 is being clocked properly by the Nano?

[MATT]

That's good, as it eliminates possible wiring errors.
Have you tried swapping out the 7660?
Also, I presume the 7660 is being clocked properly by the Nano?

Thankyou, I will try both and get report back.

[MATT]

Thankyou, I will try both and get report back.

Swapped out the 7660 and still the same. Also checked TP2 and pin 7 on the 7660 and both are 1.01Khz

[MATT]

That's good, as it eliminates possible wiring errors.
Have you tried swapping out the 7660?
Also, I presume the 7660 is being clocked properly by the Nano?

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?

[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?

[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]

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]

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]

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]

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]

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]

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?