Hello,
Until recently, the light emitted by the GR150DA of my Funke W19 was stable with a nice rose tinted glow whatever tube was tested in whateverer position of the cursor. But since a couple of days, when testing a power pentode such as a 6550 or an EL84, the light emitted by the GR150DA decreases strongly (only a very small lightning is visible in the small window) when the rotactor is in position 12. When the rotactor is switched to position 13, after a few seconds ( 10 to 15 seconds), the full light reappears and is emitted normally. In position 13, I note also that the current decreases when the light reappears : for instance, when testing a strong EL84, I measure 50mA in position 12 (light almost invisible), then 28mA in position 13 (light almost invisible) dropping to 24mA allways in position 13 when the light reappears. Note also that I checked the Va during the test : the voltage does not change when the light reappears. I measure 185V in position 12 and 197V in position 13, with a fluctuation of +-2V, whatever the light of the GR150DA.
Any explanation / advice would be welcome !!!
Vincent