At present I am rebuilding an 1990 Elektor powersupply with a triac controlled preregulator able to handle inductive loads. My intention is to modernise the design but first I want it to be operational. The preregulator does not work as intented resulting in an hot transformer.
With the DUT connected to a safety transformer 1500W I hooked up a resistive load in the form of a 230V 250W halogen lamp. I was able to look at the some signals and found that the triggering in the quadrants 1 and 2 look ok. Triggering in the quadrants 3 and 4 behave differently.
Accros R33 the quadrant 1 and 2 pulse train is visible but appart from a few blibs no action in the quadrants 3 and 4.
Looking at the discharge slope of C1 I have have the feeling that Tri2 is not firing well in quadrant 3 and 4 . But I can not find the reason.
The information from the datasheets for the BTA41-800 the TIC206D and the DB3 did not gave me any clue.
The Elektor design appears to have originated from an SGS THOMSON design found in http://www.datelec.fr/secteur/ST%20AN308.pdf
The image on the ocilloscope is measured accros C1 ( in the bridge)