wiring heaters...ugh

[amplifiednation]

My vision isn't the best as I am blind in one eye, but to me it looks like you miswired the heaters on all of your preamp tubes. Pins 4 and 5 should be wired together and the other heater wire going to pin 9 as you have them.

Ah, I think you are correct. Should I just jumper from PIN 5 to pin 4?

[amplifiednation]

I don't know how I'm gonna fit a third wire in that socket lug.

[mcrracer]

Actually the technique I use is to strip one of the wires about twice as long. Feed it thru pin 4 and hook it around into pin 5 and then fold over for a good solid connection then solder. Still only two wires. What wire gauge are you using for the heaters?

[amplifiednation]

Actually the technique I use is to strip one of the wires about twice as long. Feed it thru pin 4 and hook it around into pin 5 and then fold over for a good solid connection then solder. Still only two wires. What wire gauge are you using for the heaters?

Yeah I was just thinking that was probably the way to do it!! I'm using 20 gauge solid. I tried 18g stranded and it was just a mess.

[rp]

Take a needle nose and gently twist the pins on 4&5 so that the slots face each other, then strip one wire a bit longer and feed it thru both slots. That is the standard way. From pre to power I read somewhere that it goes 4/5 to 2, 9 to 7. Though I don't think that matters so much. I suggest using 2 diff colors so you can keep track easier. I don't like red for heaters - red suggests B+ to me, but to each his own and this is a 'wreck clone.

You should think ahead when you do heaters, it's not your heater wiring itself that will cause hum if done right, it's the relation of your signal wires and parts to them that causes problems. I like to run them out of the way marshall style, but not really applicable here.

Just an other tip, stick an old cheap tube in the socket when you solder. Mark the tube with some e-tape. Solder can suck all the way through the socket and clog the tube pin hole, rare but it happens. You'll find it when you're all done and ready to go and you'll have to pull the socket. Lotsa serious cursing.

[Structo]

I had some solder trickle into a pin holder on a preamp socket.

I just about couldn't get a tube to go in, then it went in. Whew!

Trouble is, I know that trick about having junk tubes in the sockets when soldering to them and I pretty much do it all the time.

But this time I didn't bother and it bit me.

Kind of like having an alarm on your car and the one time you don't set it, that night you get ripped off.

[mcrracer]

Solder in the pin holders is a good sign that you are putting way too much solder on your connections. Go ahead, ask me how I know this.

[Structo]

Yeah, that became quite obvious when I tried plugging a good tube in!
@)@*%*)%@

The sockets I got from a known source must of had a oil or some other contaminant because the solder would not wet properly so of course I went full guns on it.
Lesson learned.
I usually try to learn from others mistakes......

[Travst]

After using stranded wire on my first project, I figured out why my innards didn't look as good as most of the posted pics. I have since laid in a stock of solid core wire in the hopes of improving my skillz.

John

[amplifiednation]

redid my heaters thanks to everyones help and suggestions. Thank you!

Connected 4 and 5 on the preamp tubes, switched to lazy loop, color coded wire, and left more room around power amp tubes to allow for other components.

Thanks again for all the help.

[Super_Reverb]

The wires should be tightly twisted only when the two heater wires are together, but when they separate and go to the tube pins, they shouldn't be twisted.

I've even read that twisting two wires carrying the same signal reinforces the hum (actually makes it worse)

Since the heater wires are theoretically same voltage magnitude, BUT opposite in phase, the EM fields will tend to cancel out. Remember , the right hand rule says, if fingers of the right hand are placed around wire so thumb points in direction of current flow, the fingers will be pointing in the direction of the magnetic field produced by the wire. Based on this, at any point in time, the two wires will be generating EM fields of opposite polarity, tending to cancel each other out.

IMO, the parallel heater buss approach only works in one dimension, where the EM field cancellation of twisted wires works in more of a 3-dimensional way. If heater buss wires run toward the outside of each tube socket, then it seems the fields immediately over the tube socket would be cancelled. Based on the results, it sounds as if the buss approach works, but with a proper twist, it seems to me that a twisted heater wire approach would result in overall lower stray EM fields --> less induced 60Hz current in signal path. Maybe the buss approach cancels the EM field in the area immediately over the tube sockets more effectively than twisted approach?

cheers,

rob

[iknowjohnny]

I just got a look inside one of the new PRS amps....heaters wired straight to each other with no twisting.

[Ian444]

Since everyone else has had a go, here's my 2c...

There's no doubt that twisted pairs reduce interference with other wires, they have been used on aircraft and other systems for years. I'm not so keen on twisting wires together in a drill, as it forces rotation of each individual wire. I prefer to twist by hand, by hanging the pair vertically and taped firmly at the top. Then grab each wire and do one half twist and gently pull the wires out at 45 degrees to form an upside-down Y. Then do another twist and do the Y thing and so on. The 45 degrees on each wire (90 degrees between them) ensures a uniform twist. When finished, the twisted pair will only try to unravel a very small amount compared to twisting with a drill, because will be no rotation within each wire of the pair using this method. You can even put in a counter-rotation as you twist them.

[Structo]

I just got a look inside one of the new PRS amps....heaters wired straight to each other with no twisting.

Maybe they are DC heaters?

[iknowjohnny]

I suppose, but i didn't even think of that. But there are so may examples of non twisted A/C heated amps i still can't help but wonder. Some of the 18 watt guys when i was starting my first amp long ago were doing it with good results. I suppose it's more about insurance than a definate need. Like a grid resistor at the input. Most use them to insure no RF interference but some don't because i guess it's just not so common to get interference that it's real necassary.