Twincaster troubles and dumb questions

[Luke51411]

I wired up a Twincaster and it is not working as it should. When on it sounds farty and it gets disproportionately loud when I strum hard. I did it on vero using the layout here: http://miaudio.com/wordpress/wp-content/uploads/2013/11/12AU7-6111_Valve_Caster_Summary_Rev002.pdf
I did a simple continuity check between the tracks. With nothing plugged in I get about 6 ohms between the power and ground tracks. Would this be normal or is it indicating I have a short somewhere?

[GibsonGM]

Can you post your voltages at each tube pin, by number?   That would help.    Just with power on, not playing.

The 6 ohms seems off.   I'd understand about 35 ohms due to heaters, but that is way low. I suspect you have a low-resistance short, so keep on looking...with power applied (use a battery for this, not an adapter), you should see the voltage dropping if there is a short.  It will eat your battery, or even make it red hot, so be watchful.   If you really have 6 ohms, you'll pull 1.5A out of the battery so it will croak rather fast!   So go over everything really well first.   Especially pins 4+5, your heaters....if you're shorting there, you'll get the issue you are reporting.

[Luke51411]

Thanks. I finished it late last night and didn't have time/energy to do in depth debugging but this seemed off to me. I will post pin voltages tonight when I get a chance.

[Luke51411]

Voltage as follows
Supply 9.08

Dashes are not negative unless there are 2
A
1-7.19
2-0
3-.365
4- 0
5-9.08
6-4.47
7- -.1
8- 0

B
1_ 8.84
2- -.04 going toward 0 initially started near -1
3- .466
4-0
5-9.08
6-5.23
7- -.12
8-0

[zambo]

Look for a cold solder somewhere. that can cause farty and disproportionatly loud when strumming type of malfunctions. also make sure you cut the vero everywhere you are supposed to.

[PRR]

9V plate supply is sad. 9V heat is also sad. Both together is double-sad.

I'm always amazed these plans have fans.

Try a different tube (brand, era, age). Working at like 1/20th of what these tubes were made for, "minor" differences in cathode-stuff and playe-alloy can be major differences.

Try 12V power, at least the heat will be right.

[Luke51411]

I'm planning on running it at 12v just plugged it into 9 for troubleshooting. It's probabably a cold solder... Accidentally ordered solid core wire...

[GibsonGM]

9V plate supply is sad. 9V heat is also sad. Both together is double-sad.

I'm always amazed these plans have fans.

Try a different tube (brand, era, age). Working at like 1/20th of what these tubes were made for, "minor" differences in cathode-stuff and playe-alloy can be major differences.

Try 12V power, at least the heat will be right.

+1    I've done a few at low voltages and none of them were made permanent.  Just didn't have any character, IMO...no headroom and onset of clipping was on the molecular level!  Very sudden, like Si.

Nothing is wrong with solid core wire in a non-moving part of a circuit.  I use it all the time.

This could be a good learning process, Luke, so don't give up.  I'd try audio probing your circuit, just for grins.  Listen to the output at C2 and C3 with a tone or guitar being played into the circuit.  Look up "audio probe" if you don't know what that is, and only use it on LOW VOLTAGE circuits such as this one.     You might find that one side is OK, and the other is farty, and you can mess with it to make it less so.

Mess with the gain pot, too, and see what happens...I'm curious if that is hooked up right. 

[Luke51411]

Solid core just seems a bit more prone to cold joints in my experience is all. I built an original VC and I enjoy it quite a bit so I figured I'd try out the dual version. I will break out the trusty audio probe when I get a chance. This was my first Vero project and I set it up on the wrong side of the perf so I had to install the parts mirrored. With that being said, I'm not highly confident that everything is in the right place. I will have to check through everything again. Also, I found that I have one set of 2 12AU7 tubes and another set of 2 12AU7A tubes would that make a difference? I tried the 12AU7 tubes and they seemed to sound marginally better but still pretty bad. They all look like used tubes while the tube I used for my first VC I'm pretty certain is NOS so maybe the difference is there? Lots of things to try out I guess to see if I can coax a bit of tone out of this beast... Haha

[PRR]

You *need* flux to solder. Otherwise you are just blobbing solder onto the tarnish/oxide that coats any metal.

Flux-core is convenient.

If you got no-core, you need some other flux. You can get liquid and other forms.

But flux-core is usually best.

[Luke51411]

I have rosin core solder and solid wire instead of stranded. I can see where what I said was kind of ambiguous.