Merci Jean-Paul
Probing the TGA signal from pin 18 of U500, the triggering waveform there is as I see it on the screen i.e. intermittent. So it looks like U500 or circuitry before it in the trigger path is faulty.Time to read the theory of operation of the trigger circuitry I guess.
Something is borderline as triggering is OK at slow sweep speeds but not at < 1ms/cm.
Keith
