Replaced q-1 & q-2, no improvement.
On a bright note, I bought a Hakko FR-300 and used it to remove the SK369BlLs. It's a joy go use . The old FETs slid out easily and will fight another day.
So, what do you suggest for the next move?
Thanks
I'm using a 1.0 uf, 400 vdc Clatrity at c3. I've got two pairs of 0.22 uf film caps (Mundorf & Cardas) that I could use to test. (Single or parallel.) Would that be sufficient?
If so, I'd probably do that before pulling the remaining fets.
0.1uF is the recommended max for C3. But for distortion source finding purposes, not for permanent use, a 0.22uF will show if C3 was the problem. You wrote you show it around there with some probe. Although if without any info more than it got connected to a work in progress tube pre and then acted up I would first be suspicious of the output stage.
Already did that successfully in the past... just be sure to not overheat the legs of the 170.... I use miniature alligator clips that i put in each fet leg before soldering
Not a bad addition in general since you got some chokes lying around I presume. But LC maybe will drop more volts than aspiring to? OK, then a higher secondary Tx you may say. Anyway there is Duncan Sim before drilling the box or perform some measurements when still all that stuff is loose.
I have some different filament chokes to test with, generally with lower DCR. Ideally I would prefer a common mode like http://www.lundahl.se/wp-content/uploads/datasheets/2733.pdf. Maybe I can special order one with lesser gap for more inductance. Then I can level off with RD/link. I have some selectors on back order so the boxing will not be ready until end of summer anyway.
