Everything seems fine with the valve, it gets warm when it’s been on. I have noticed that the 27R does get really quite hot however further up the thread seems to suggest whilst this isn’t ideal it’s not awful.
Unfortunately I do not have a scope no, I really should grab one because it would make debugging things like this a lot easier, something to add to the list!
Think we’re on checking the circuit and components and continuity. It is very odd that it was working fine a few days ago but has decided now is the time to shit the bed!
Two 47 ohm resistors in parallel would give you 12/(47/2+12.6/0.15) = 112 mA through the circuit, and each resistor sees half of that or 0.056×0.056×47 = 0.15 watt which is well within spec for a 1/4 watt resistor. See the graph here for how using more resistors lower the power dissipation for each individual resistor.
If you’re still concerned, you could try shorting the resistor. The valve can handle the full 12 V just fine.
@CTorp torp did you manage to solve this? im a little bit stumped to be honest. the status led on the front panel is wired straight to 12v via the switch im not sure why it would be doing such a thing apart from solder joints. which valves are you both us9ing??? maybe they are the same? and we could go from there?
It works when you touch the tube leads? My tiny imagination can only think of 2 reasons for this:
Something bad happened when you soldered to the tube leads (like something came loose inside and you’re wiggling it to touch
(In the laser cutting world when you go to replace a CO2 laser tube they have all kinds of warnings about not soldering to the tube lead)
Is it a grounding issue?
12AX7/ECC83 is just supposed to be a US/Rest of the World name thing.
thats rather odd. so in order for it to work you have to boost the signal of the oscillators etc? as in if you plugged in an oscillator straight in it would not work?
rather odd im trying to figure out why this might be the case, in normal function you plug in anything from a contact mic up to an oscillator it will make it louder, I dont think there would be an instance it would make it quieter as the boost circuit way beyond the headroom of the synth so im trying to work out why yours is not doing that
Yes, my external synths like microbrute, ms-20 have noticeable distortion and the led behind the tube lights up. With my kosmo stuff there is no distortion and the led doesn’t light, until I boost the signal. My diy valve distorting vca also doesn’t have this problem.