I was blessed by someone and was given a beautiful 1590A Phase 90 PCB. The Q2-Q5 FETs were SMD MMBF5458. This is my first Phase 90.
I got it all soldered up and started trying to bias by ear, and there's only about a 0.0000000001 spot where I get much of a sweep. I DO get a sweep, but it's not very intense like I'd expect.
I was told that I don't have to match the SMD JFETs because the tolerances are much tighter.
I also have a Rigol Digital O'Scope, but I have no idea how to use it to bias. (I would LOVE it if someone had a tutorial on how to do this.)
Am I completely missing something here? Maybe I really DO have to match the JFETs? Maybe I just have to find a sweeter spot that's more like 0.000000000000000000001?
(I've had too many boards not work lately. I hate being in a rut.)
I got it all soldered up and started trying to bias by ear, and there's only about a 0.0000000001 spot where I get much of a sweep. I DO get a sweep, but it's not very intense like I'd expect.
I was told that I don't have to match the SMD JFETs because the tolerances are much tighter.
I also have a Rigol Digital O'Scope, but I have no idea how to use it to bias. (I would LOVE it if someone had a tutorial on how to do this.)
Am I completely missing something here? Maybe I really DO have to match the JFETs? Maybe I just have to find a sweeter spot that's more like 0.000000000000000000001?
(I've had too many boards not work lately. I hate being in a rut.)