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I read somewhere that the stock fly wires that go from the power tube sockets to the PCB on the Fender Red Knob Twin are 22 gauge solid core 600v. Is this correct? Or is it another rating and gauge? 600V, 22 AWG, 19 strand wire???
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OMG, it doesn't matter. Use what you have that fits. Solid wire is easier to bend into a shape and stay there, but stranded wire is easy enough to deal with, so take your pick.Education is what you're left with after you have forgotten what you have learned. -
i have 22 gauge solid radio shack hook up wire but 300v. Should i get 600v?Comment
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300v would be too low for my liking, especially since the plate voltages are something like 480v. Depends what you run it next to - the rating is for the insulation and is what the manufacturer has tested it to. A wire will handle excessively high voltages just fine if it's hanging in the air, but as soon as you bring it close to a grounded chassis, or wire/component/body that's at a lower potential difference, that's where the insulation rating comes in.
Either get some rated at 600v, or use stranded with the correct rating if you have some.Comment
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Really??? 22 gauge eh, ain't that kind of small for high voltage work? Shouldn't it really be something like 18 gauge or like that? 22 gauge, mmmm, that's like 9V battery wire or there about's, not really suited for the plate voltage on a 6L6 I would think.Originally posted by jalexquijano View Post... That's $1.00 for the chalk mark and $49,999.00 for knowing where to put it!Comment
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wire info per our friends over on the AX84 site. For wiring inside chassis
gage current capacity
18 16 amps
20 11 amps
22 7 amps
24 2.2 amps
All data from 1978 ARRL Radio Amateur's Handbook or computed from data there.
The wire does not care about the voltage, just the current...The wire insulation worries about the voltage.Comment
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Wire size is not about voltage, it is about current. The high voltage of B+ is only a few milliamps - thousandths of an amp. It will not stress #22 wire in the slightest.
And as mac's numbers point out, it won't be bothered by even heater current.Education is what you're left with after you have forgotten what you have learned.Comment
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Yeah, you're right of course and I certainly can be an idiot sometimes but for argument's sake let's assume that 6 amps of B+ are flowing and not just a few milliamps. Would a 7 amp capacity #22 wire be able to handle that much energy? Wouldn't that be welding machine levels of voltage and current? I just think you can't separate voltage and current like that, you need to take both into consideration when determining how big a wire you use.Originally posted by Enzo View Post... That's $1.00 for the chalk mark and $49,999.00 for knowing where to put it!Comment
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The limitation in the HT circuit is the transformer secondary. A sudden short could pull a momentary high current from the charged filter caps and after that you're down to the current capability of the wire used to wind the secondary, and that's way finer than #22.
Think about the wiring inside a vintage Orange amp and how that holds up. They even used #22 on the primary.
Interesting that you mention welding levels of voltage - welders use comparatively low voltage - my stick uses 45/70v, my MIG about 26v, and my old spot welder used less than 2v.Comment
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But we can't assume 6 amps of B+, to do that, the mains draw would be 3-4 times that amount. Unless we have a tin foil fuse... That sort of current just isn't available in the HV winding.Yeah, you're right of course and I certainly can be an idiot sometimes but for argument's sake let's assume that 6 amps of B+ are flowing and not just a few milliamps. Would a 7 amp capacity #22 wire be able to handle that much energy? Wouldn't that be welding machine levels of voltage and current? I just think you can't separate voltage and current like that, you need to take both into consideration when determining how big a wire you use.
And as Mick points out, the HV winding resistance will limit current as well. As soon as you try to haul such current out, the voltage in the winding will plummet.
But to answer your point, yes the 7A rated wire will handle 6A just fine.Education is what you're left with after you have forgotten what you have learned.Comment
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isnt there a big derating factor for twisted wire ie heater wire becaues the two wires must share the same space and the two wires heat each other?Originally posted by mac dillard View Post
There was a really good explanation about this by Gingertube on a thread about six months to a year ago but I cant find it. he posted a chart that had ratings for solid and stranded core wiring at different gauges and I think by individual wire, two wires twisted, 3 wires, etcLast edited by nsubulysses; 09-02-2017, 05:25 PM.Comment
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OK, but how much heating will there even be? It is one thing to twist together giant power cables, but the wires down to three 12AX7s carries less than an amp.Education is what you're left with after you have forgotten what you have learned.Comment
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The equation for wire resistance is R=a(l/d) where a is the coefficient of resistance for the wire material..l is the length and d is the diameter. For copper a is 1.72 x 10-8. (10 to the minus 8). Resistance will change with temp. but for short runs in a chassis you are not talking much. If you are really concerned with this add up your tubes heater requirements, double it and see what amperage is required. As for two wires twisted together I would be more concerned with insulation breakdown than anything else but at 6.3 volts it is not a problem...If you really want to get into something tricky take a look at resistor voltage rating. I'm not talking about voltage drop across the resistor but the voltage applied to the resistor. Most are about 350 volt. and we use them in 400 volt systems all the time.Comment
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Just a word of caution when using solid core wire.
Be very careful when removing the insulation.
Any small 'nick' in the wire will set it up to break there.Comment
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