Pegasus Astro Forum

Hi,

I have my astro camera connected to one of the 12v output on my PPM. I have two dew heater bands connected to the dew control RCA outlets. When dew control is switched on in the Pegasus Astro software, it creates a buzzing noise coming from the camera. The sound intensity varies accordding to the power I set in Pegasus Astro software (in auto mode or set to certain values is when it is most audible).

I have read in another post that another user had a similar issue and it was caused by the dew heater itself. I'm not really keen on replacing my dew heaters since they are brand new. Is there some sort of modification that I could do on the PPM (soldering a capacitor on the board or something) to solve this? Adding ferrite chokes on the dew heater cable ends doesn't help.

I'm also wondering if changing the dew heater's cables and plugs to better ones (shielded cable, thicker gauge, gold plated plugs...) could fix that, but 'm skeptical and don't wish to modify them if it makes no difference.

Thank you.

A capacitor will not help there. The PWM modulation in Dew Outputs should work without capacitors.
As there is a different circuit between heatets (pwm duty cycle %) and 12V Outputs there must be something else.
What kind of PSU do you have?

The PPM is drawing power from a portable Lithium power station (DC 12V cigarette lighter socket).

Maybe the inverter of the LiPo battery tank causes this issue.

Negative. I tested a separate power supply to the PPM and the problem is still there.

On either power sources, when the dew control is set to full power (255), the buzzing is no longer audible.

We have never experienced this issue. The only I can think of is a ceramic capacitor which resonates in audible frequency. It should not be a problem (only audible noise)

https://www.murata.com/en-sg/support/fa ... /char/0020