22 gauge in heater wiring..?

[überfuzz]

I received a shipment with, amongst other things, wire. I ordered 18 gages push-back wire to use in heaters. Tiered as I was I checked it hasty and started to solder. Now when I had a look, not blurred by sleepy eyes, I see that it is 22 gages.

Do I need to rewire it or is it safe to use the wired shipped to me..? (I'll mail the company to, asking.)

[Wilder Amplification]

I received a shipment with, amongst other things, wire. I ordered 18 gages push-back wire to use in heaters. Tiered as I was I checked it hasty and started to solder. Now when I had a look, not blurred by sleepy eyes, I see that it is 22 gages.

Do I need to rewire it or is it safe to use the wired shipped to me..? (I'll mail the company to, asking.)

It depends on what tube types you're running but in a typical Marshall 22 gauge is fine for heater wiring. It's rated to carry 5-7 amps and you're using it in very short lengths. Only the wires direct off the transformer are carrying the full heater current and the current that each pair of the string has to carry drops progressively as it passes each tube socket.

[macdillard]

From our friends over at AX84




18 16 amps
20 11 amps
22 7 amps
24 3.5 amps
26 2.2 amps

[Chuck H]

No problem with current but there is an appreciable voltage drop. At a glance it's easy to ignore thinking 'well there's only a few short runs between the sockets' but when you consider that they are twisted and routed it can end up being a couple or even a few feet of wire. I just did an amp with 22ga but I used a Hammond PT with the 115V primary. So the small voltage drop was insignificant and perhaps even helpful. But if your heaters were already low, for example, it could be a problem. Just mentioning it.

Chuck

[Chuck H]

Just an update...

Using an on line calculator the voltage drop for three feet of 22ga (one lead of the twisted pair) used for a pair of 6L6's and three 12ax7's is .299 volts.

Four feet of 22ga for 4xEL34 and three 12ax7's (which is pushing max for current capacity for 22ga) would be a drop of .93 volts.

And all points in between. So IF you already had a low heater voltage, like 6.1 volts, a half a volt starts to matter as that would exceed the 10% tolerance.

Chuck

[überfuzz]

Chuck - Thank you for the info. When the time comes I'll measure the voltage drop. If there's no problem I'll do it to ease my curiosity.

The retailer said that it shouldn't be a problem...

[loudthud]

If you find the voltage drop is too much, you don't need to replace all the wire. In many amps the transformer leads go to the pilot light, then to first power tube, next the second power tube, then on to the preamp tubes. You would only need to replace the wire between the pilot light and the two power tubes. The preamp tubes don't draw much current so #22 is fine there.

[Chuck H]

+++
I failed to mention that.