Static noise on Audio channel

[VICtor64]

I recently installed these RF bypass board on two different C64 mainboards

Both are causing a kind of static noise on the audio channel, even when no sound is playing.
Can anyone provide some guidance on what could possibly be wrong?

Additional information:
– Board revision 250425
– The problem persists even with the SID removed.
– The problem does not exist with the original RF modulator installed.
– I have already checked for shorts on the RF bypass
– GND1 is connected to ground

suggestions welcome

• This topic was modified 1 year, 9 months ago by VICtor64.
• This topic was modified 1 year, 9 months ago by VICtor64.

[BuckoA51]

Very strange, we’ve never had issues with audio reported before in over 100 boards sold.

Would it be possible for you to try a different AV cable?

[Anonymous]

Bumping an old thread. In looking at your picture closer, it seems you may have excess solder on the ground pin. This, itself, isn’t an issue. But if you also have excess solder on the Audio Pin, which is the 1st pin on the second (right side) pin header, then you could be bridging audio to ground. This will cause a buzz even if the SID is removed. I would check continuity from pin 5 audio to ground. There should be none. If it’s shorted, then there’s your problem. You can also check it at C13. There should be no contact to ground.

[Author]

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