Tevion LCD 6722 sizzling from speakers

[Davy]

Have Tevion 6722  LCD fitted with CV106LT V3.0 main board slight sizzling from speakers.

This set uses a TDA1517 audio o/p chip, I suspect decoupling capacitors since the noise sounds like switch mode type ripple from one of the  dc-dc on-board converters.

Can anyone throw light? Thought I ask before 'going on safari'. This is a 12V telly..... seems to run OK, I did swap the inverter because one of the transformers was rattling... the protection plastic looked 'cooked' but yet the set worked OK, nope, not the power supply I tried another.

Dave

[Davy]

Sorted...!

Sizzling noise or amnesia (losing channels) Scope 3.3V rail, there are three voltage test points just above the keyboard connector socket just behind the card slot connector these are marked 12V, 5V and 3.3V..... be very careful, the test point behind the 3.3V carries a higher voltage, the 5V middle one is linked across.

A dirty big ugly waveform appeared on the 3.3V DC rail.

Change C10, 100u 16V and C84 right next door a 470u 16V, use low ESR electrolytic capacitors, these are situated near the toroidal core inductor and you'll cure the low level sizzling from the speakers.... and cure channel loss.

Edit:
I forgot to mention, the two caps. in question looked alright no signs of distress.

Dave