I wonder if anyone could be so good as to HELP
I built the Korg Nutube preamp last year. Everything went well, readings and bias all good - I used it, it sounded great!
I didn't then use it for a while as i was working on a power amp I intend to pair with it (Quad 405-2 with Snook mods). Thats finished, I went back to hook up the pre amp to find only one side of the Nutube is lighting up. It looks like the very thin filament is broken. I'm reading 9v on T6, its 0.7v on T7. T8 is 20v rather than the 9.5 the bias was set up at. I figure I will need to troubleshoot before replacing the expensive Nutube could anyone suggest a likely cause?
I built the Korg Nutube preamp last year. Everything went well, readings and bias all good - I used it, it sounded great!
I didn't then use it for a while as i was working on a power amp I intend to pair with it (Quad 405-2 with Snook mods). Thats finished, I went back to hook up the pre amp to find only one side of the Nutube is lighting up. It looks like the very thin filament is broken. I'm reading 9v on T6, its 0.7v on T7. T8 is 20v rather than the 9.5 the bias was set up at. I figure I will need to troubleshoot before replacing the expensive Nutube could anyone suggest a likely cause?
Attachments
regarding heater , T6 OK reading
if you have all F points in range of 24V, everything is good and "only" tube is whacked Dodo
if tube is Dodo, expect whatever gibberish values for T7 and T8
though, alive side/channel should stay in biased range ... but no use of fussing too much - everything is directly related to 9V1 figure, and if that is OK, you can blame tube for any mishap
all ref. to pdf in post #1, B1 with Korg Triode
if you have all F points in range of 24V, everything is good and "only" tube is whacked Dodo
if tube is Dodo, expect whatever gibberish values for T7 and T8
though, alive side/channel should stay in biased range ... but no use of fussing too much - everything is directly related to 9V1 figure, and if that is OK, you can blame tube for any mishap
all ref. to pdf in post #1, B1 with Korg Triode