Triac light control : flickering

[tynnor]

Hello,
I have always used the following schematic to control my lighting in my application :

I have changed the lights for a 100W sodium-vapor lamp and a 39W tube lamp. Both have an integrated electronic ballast. And now, even when optotriac is off (I assume it from the input led command I checked with a scope), the tube lamp is blinking ! If the 100W lamp is the only one plugged, there is no blink, but the light is slightly on.
What I tried:
- Open the snubber to identify a possible leakage
- Change R_snubber to 360 Ohm
- Put an R2-C1 filter like the following one (39 Ohm - 100n and 39 Ohm - 10n) to dump any oscillation. It was even worst

- Add 10kOhm load across the triac terminals to dissipate a possible leakage

Nothing improved the situation.
Unfortunately, I don't have the stuff to make scope measurements in this part of the board, so I am working like Gilbert Montagné is playling piano

Do you have any idea from where the problem can come from ?
Thank you

 

[Easy peasy]

Really your snubber cap is too small - ideally at least 47nF 375Vac and 100 ohms - but the leakage of this size snubber may power your load slightly

but to avoid false turn ons - place a 47nF or 100nF cap across the RGK.

 

[tynnor]

I added a 100nF across Rgk, it's a bit better but I don't think it is a good idea for gate inrush current (that's why R2 is here)
I don't have a lot of X2 cap and suitable resistors with me. I tried a snubber 39R-110n, 330R-10n.
Increase C1 seems to worsen the situation whereas I thought it was the key component in my problem

 

[Easy peasy]

I added a 100nF across Rgk, it's a bit better but I don't think it is a good idea for gate inrush current (that's why R2 is here)

- bollox - there is no mechanism to increase gate inrush current by adding this cap

- Remove C1 ( this is the cap supplying gate current )

- Just use a standard snubber ACROSS MT1 - MT2, AND the drive in the 1st pic ....

- bump up the gate capacitance to 220nF .... do not add RGK.