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trsomian · 13th Feb 2018, 1:14 pm

Firstly, I don't normally dabble with TVs very much, but I have one of the above which largely works, but has audio hum when the picture is bright (not when the picture is dark. Seems like an electrolytic drying out to me; do others agree? The picture doesn't misbehave though.

I have downloaded the service manual, and it seems the audio is all in a TDA8191, which runs from a 20V supply off the main SMPS Obviously the smoothing capacitor for that output is a likely villain. I assume that the main DC link capacitor after the mains rectifier is good because the picture is OK.
Why would the hum change with picture brightness though?

All guidance and ideas welcome

13th Feb 2018, 1:14 pm	#1
trsomian Hexode Join Date: Oct 2010 Location: Box End, Beds. UK. Posts: 271	Philips SG90AE hum Firstly, I don't normally dabble with TVs very much, but I have one of the above which largely works, but has audio hum when the picture is bright (not when the picture is dark. Seems like an electrolytic drying out to me; do others agree? The picture doesn't misbehave though. I have downloaded the service manual, and it seems the audio is all in a TDA8191, which runs from a 20V supply off the main SMPS Obviously the smoothing capacitor for that output is a likely villain. I assume that the main DC link capacitor after the mains rectifier is good because the picture is OK. Why would the hum change with picture brightness though? All guidance and ideas welcome