So I'm building this amp, and in spite of all advice, I don't know a great deal about how they work. But I have guys who do know on hand to help me go over everything very thoroughly before any voltage is involved.
I've gotten a little bit stuck though, The two leads coming from the pilot light are labelled "To all fils" then there are pins labelled "fil" on all of the tubes. Now how do i go about joining all fils to the pilot light?
Interesting question, I don't reckon I know, though...
Just with wire. Traditionally you use green for filaments. Its wired in parallel so that there are actually two sides to your filament feed, each feeding one side of the tubes. You'll want to keep the power tubes in phase (ie. pin 2 on one tube connected to pin 2 on the other). With preamp tubes it doesn't matter so much but I always try to keep them like that for neatness.
Fils should be as far away from other wires as possible and either should fly half an inch above the tube socket or should be tucked under the edge of the chassis.
I'll try and find some pictures.
Best, Tommy.
Here's a picture showing the filament wiring on my latest blackface build.
Tommy.
And another.
Good luck! Tommy.
And, just to fill your head with needless pictures of amps, here's a narrow-panel Bassman's filaments.
I find that each option is quiet in a Fender but I imagine that in an 18watter you might want to suspend them above the tubes to keep it as quiet as possible.
Tommy.
Another thing you might consider is using two separate colors (like green and white) for the filament wires, that way you can have each preamp tube wired identically. That's what I normally do. It's supposed to reduce heater noise.
Yup, you can do that. I just check which wire is which with my meter before soldering.
The two 'fils' (or heater) leads come straight off the transformer, and supply either side of the bulb directly. The heater leads then go to the filament terminals on the valve sockets. On my Plexi rebuild, I also connected each one to ground via 100 ohm resistors.
When wiring the heaters I used single-core wire (18 gauge, I believe) and twisted it quite tightly. If you leave them loose, you'll get AC hum through the speakers. The reason for using single core was to make the wires as rigid as possible so that they arch about 1.5" above the circuit board without dropping down. (Not sure exactly HOW effective all this is, but suffice to say that my amp is 100w and at full volume, there is NO buzz and precious little hiss through the speakers...)
Hope that helps...
My method is to take a piece of green wire and fold it into two even portions. I use a pen and make a line down the length of one of the folds and then I twist them together tightly.
I clamp mine in a vise and twist the other end with a drill.
Hey Tommy, is that a picture of my amp?!
