I just completed a Ceriatone C-lator build, which is a Dumbleator clone. I think the schematic is almost identical to this:
The layout for the C-lator is here:
The strange thing is that the unit actually still functions even if the standby switch is in the off position. I'd like to know why this is and how I can fix it.
It seems that the C-lator employs a voltage doubler. The standby switch comes in between the two caps that are doubling the voltage and the 0v tap of the 135v winding on the power transformer, which is the return path for the transformer. I don't know how there could still be voltage flowing if the return path of the signal to the PT is cut off.
Last edited by itsgiusto on Mon Jan 04, 2021 5:01 am, edited 1 time in total.
As I recall those filter caps don't have bleeders. It may be functioning because of residual voltage left in the caps. It shouldn't function for long if that is the case.
CW
Charlie Wilson wrote: ↑Mon Jan 04, 2021 6:28 am
As I recall those filter caps don't have bleeders. It may be functioning because of residual voltage left in the caps. It shouldn't function for long if that is the case.
CW
Yeah, I think that's the "issue" as well. Guess it's a non-issue, really. The weird thing is that when I put it into standby, the volume drops and keeps dropping, but never actually hits silence.
But basically, I just wanted to make sure the build is okay and that this is not indicative of some greater problem. If it's not, then I don't really mind the non-silence on standby. I probably won't even use the standby switch anyway.
Charlie Wilson wrote: ↑Mon Jan 04, 2021 6:28 am
As I recall those filter caps don't have bleeders. It may be functioning because of residual voltage left in the caps. It shouldn't function for long if that is the case.
CW
You are right Charlie, it is a flaw in the circuit. The caps only discharge over the tube. When switching to standy, the voltage drops but the tube will keep working. When the voltage drops, the current drops so the caps will unload slower. This proces continues for a long time since a tube can still work at a low voltage, while the current flow gets very small. The tube will eventualy distort the signal more and more and after a very long time die out.
Charlie Wilson wrote: ↑Mon Jan 04, 2021 6:28 am
As I recall those filter caps don't have bleeders. It may be functioning because of residual voltage left in the caps. It shouldn't function for long if that is the case.
CW
You are right Charlie, it is a flaw in the circuit. The caps only discharge over the tube. When switching to standy, the voltage drops but the tube will keep working. When the voltage drops, the current drops so the caps will unload slower. This proces continues for a long time since a tube can still work at a low voltage, while the current flow gets very small. The tube will eventualy distort the signal more and more and after a very long time die out.
I had one of my dumblelators in a storage, after 6 months(!) still had over 100v on the PS.
Charlie Wilson wrote: ↑Mon Jan 04, 2021 6:28 am
As I recall those filter caps don't have bleeders. It may be functioning because of residual voltage left in the caps. It shouldn't function for long if that is the case.
CW
You are right Charlie, it is a flaw in the circuit. The caps only discharge over the tube. When switching to standy, the voltage drops but the tube will keep working. When the voltage drops, the current drops so the caps will unload slower. This proces continues for a long time since a tube can still work at a low voltage, while the current flow gets very small. The tube will eventualy distort the signal more and more and after a very long time die out.
I had one of my dumblelators in a storage, after 6 months(!) still had over 100v on the PS.
Haha, that's hilarious!
PicknStrum wrote: ↑Mon Jan 04, 2021 5:05 pm
I'm curious if adding bleeder resistors to the caps in the doubler circuit would help...this is me just spit-balling - I have no idea.
It probably would help, but as mentioned above, if the circuit is working correctly, I don't actually care if the standby mutes the sound or not. I was just worried that this was indicative of a larger issue or something, wanted to find out if this was normal.
drew wrote: ↑Tue Jan 05, 2021 1:19 am
Why does a Dumbleator need a standby switch?
IMO, it 100% does not. The only reason I built it with one was because there was already a hole drilled for it.
People talk about tubes "cathode stripping" shortening tube-lifespan if you don't use a standby switch, and that would apply to a Dumbleator as well if true. However, I've never encountered such issues, and from what I hear the concept does not apply to guitar amp tubes. But to each his own, I'm sure using the standby switch makes some people more comfortable.
Put in a few bleeder resistors in and call it. I have never heard of cathode stripping occurring on pre amp tubes the voltage is too low..AFAIK the only time you really have to worry about it is in like say high powered transmitters/Amplifiers with exceptionally high plate voltages that run constantly or long periods of time.
I rarely if ever use my stby on mine..
Tony
" The psychics on my bench is the same as Dumble'"
) from this site.
