If you have a new pair from Spencer just replace the blown ones with the new pair.
L to R channel Jfet Idss doesn't need to be matched, the bias pots take care of that. What does matter is a good match between the N and P channel Jfet, on that channel's board.
Easy way to figure what each resistor should drop is to divide rail voltage by total resistance. This wil give you your total current through that leg. Take that amount and multiply it times the resistors and you wil haev the Vdrop you shuld see. Your configuration should yield slightly less than 15V, i believe.
I am not going to say that it is 100% that your Jfets are dead, but it seems like all you are getting is the Vbe drop of the bjt's. Perhaps others will confirm. IN theory, a biased Jfet shoudl provide resistance of some kind. This is how the voltage is formed at the drain. It appears yours are a dead short.
hmm I wonder how that happened. other than the first turn on and the voltages I kept seeing it was never powered before?
How would I test to see if the jfets are dead? I never saw any magic smoke
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I'm lost without link to ref. schematic , considering all iterations (of everything) floating around
well it should be NP's F5TV3 schematic. However, the board was purchased on DIYaudio's site its V2.0. (toecutter board) hopefully there wasn't any major changes between that one and the one currently selling now.
I'm back , after some time
pull all semis out , and test them
for Jfets - search for JFets matching - all you need is 9V battery and DMM
for mosfets - something more , but you'll manage
though , even if that seems complicated and over the top for one "simple repair" , you'll learn something and use these procedures later
pull all semis out , and test them
for Jfets - search for JFets matching - all you need is 9V battery and DMM
for mosfets - something more , but you'll manage
though , even if that seems complicated and over the top for one "simple repair" , you'll learn something and use these procedures later