Dumbleator Cap Voltage Ratings

[TheHandsomeOrk]

I'm going to try my hand at building the series/parallel dumbleator but only have 0.47uF/100v caps. What voltage does these caps need to be for that circuit. Thanks

[bluesfendermanblues]

I'm going to try my hand at building the series/parallel dumbleator but only have 0.47uF/100v caps. What voltage does these caps need to be for that circuit. Thanks

No problem at all.

The 0.47 uF at the V1 cathode is only 'seing' about 32 volts DC. Way below the 100 volt safety margin. Same applies for the 0.47 uF at the V2 grid.

Also the 0.22 uF in the V2 LNFB, only has 40 volt DC across its pins (not measured to ground, but across its pins), so you can use a 100 volt version with no problem.

Disclamer: Take care with the lethal high level voltages in tube amps in general. If you are uncertains about anything, take it to a tech for approval prior to connecting the apparatus to high voltage.

[angelodp]

Sounds like a plan. Please post some gut shots as there a few of us, less adventurous, that are eager to see one.

best A

[TheHandsomeOrk]

Thanks bluesfendermanblues.
Is the bypass cap 47uf or 4.7uF? 47uF seems large on a 12ax7.

Yes I will post gut shots as soon as it's completed. They won't be pretty
as I'm trying to keep the cost under $20. I'm using parts that have been given to me over the years and spare parts from the junk draw.

[Pete]

Is the bypass cap 47uf or 4.7uF? 47uF seems large on a 12ax7.

47 is correct, there are some schems around with errors, this recent thread shows a good schematic I believe:http://ampgarage.com/forum/viewtopic.php?p=46373#46373

[Structo]

Sorry wrong thread.

[TheHandsomeOrk]

Thanks Pete

Is the bypass cap 47uf or 4.7uF? 47uF seems large on a 12ax7.

47 is correct, there are some schems around with errors, this recent thread shows a good schematic I believe:http://ampgarage.com/forum/viewtopic.php?p=46373#46373

[angelodp]

Are you referring to the 47uf 50v which is parallel to the 1.3k resistor.

[TheHandsomeOrk]

angelodp, Yes that's the one.

[TheHandsomeOrk]

After sorting parts here's what I've come up with. In order to keep the cost under $20 and to fit a transformer inside a single rack space ,
I will try back-back small xformers. I found a choke (working pull) from a blues deville which may be suitable (140R), a mixture of caps (Acushnet(usa) and panasonic polyprops), mixture of resistors (CFs,CCs,MFs).
Power supply will be something like this (see attach). Will have to juggle drop string and plate resistor to get correct voltages which may be a deal breaker. I could always buy an xformer i guess if it can't be done.

[Structo]

That should work.
I would leave the plate resistor at 100K for the gain factor, but just adjust the dropping string.

I used the Fender Reverb PT and made my power supply from the bridge rectifier onward about how you have yours.

[TheHandsomeOrk]

Thanks structo.