Henry,Good news, I moved the sockets back onto the board as George suggested a the distortion is gone. I guess there was oscillation due to moving the sockets off the board. I am not sure why the radio test didn’t pick it up. It sound better then when I started so I seem to have fixed the other weak signal/distortion issue along the way. I am still worried that the sockets are too tight and am thinking of how to stabilise that area of the board - perhaps adding a post.
I'm so glad that you fixed it.
Regarding a post, I'm thinking about using fiberglass posts or stakes that are normally used to support plants as shown in the link. I'm not sure this is something that would be available in Britain but it might give you some ideas. I like the fiberglass solution because it's stiff and has a higher temperature capability than most plastics. They are probably made with polyester resin instead of epoxy like the fr4 material used in pcb material, but it should be more than high enough temperature for our use. With a solid post you can drill the end and mount it with a screw from your top or bottom plate.
https://www.walmart.com/ip/Eco-Frie...nch-Dia-by-N-LOVA/301283862?classType=VARIANT
Jac
Other than jumping the IC3 and going AC fils directly is it possible to get regulated 6.3v fil voltage with 6.3v AC secondaries?
Looking at the LDO V-reg. datasheet it looks like that is not possible. I want to run a 6B4G on an adapter…..
George,OK, why did a box containing 5 50L6 tubes, 10 50FE5's, 10 12AU6's and 10 12AW6's show up at my house today, and another pair of Ebay scored 50FE5's show up yesterday? No, they are not for old radios, or any old stuff. There is another box full of stuff that I fetched from the storage trailer destined for the same place. To me, the real question is what did the US military do with 50L6 tubes in 1987? That bar code is an FSN (Federal Stock Number).
This old unfinished breadboard might provide a clue or two.
That looks like the makings of a great design. Keep it up and thank your for your work for all of us!