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10-22-2023, 12:01 PM
Hi Guys
Using the $33 eyelets (1/8" dia) and appropriate wire gauges for the circuit, there is usually no problem having quite a dense number of lead outs.
Most component leads are around 0.032" or so, maybe 0.047" for a filer cap lead, and the bus wire is usually #24 (solid-wire that is tinned). All of our kits and projects specify #22 hookup wire and shielded calbe is #22 or #24. I use #24 coax and 2-conductor shielded wire.
For some reason, a lot of hobbyists think that they need fat wire for high-voltage, and then buy #16 or larger wire. This is the wrong way around. High-voltage needs better insulation NOT a thicker conductor. Current in a tube circuits is a few milliamps or less, wgich is easily carried by very thin wire that is actually more difficult to work with and does not come with high-voltage insulation. There is a common very-thin wire that is solid-core and Teflon-insulated used for wire-wrapping - an old way to prototype and to construct low-voltage circuits.
TUT3 gives a list of wire gauges and their current capacities. These ratings are conservative and assume an insignificant temperature rise inside the wire caused by heating by that current. So, #22 is rated at 2A, which is high enough to feed the heater of an EL-34 or 6550 PROVIDED that is the only current being carried by this wire. TUT3 shows wiring solutions that allow all wiring in an amp to be small-gauge. You can find ratings charts where #22 can carry 90A - but this is with a temperature rise in the wire of nearly 100C !!! We do not want this in our builds.
The other thing to do is to tin the wire ends. I use stranded wire only, except for bus wire and links made from cutoff resistor leads. I twist the strands and tin it before making the connection to switch lugs, or for insertion into PCB pads or component solder lugs. The tinning should be "light" inasmuch as the solder should flow evenly over the wire and not obscure the individual strands. There should not be any "globs" or thick parts of excess solder. This tinning step helps keep each wire unitised and they will be easier to poke into an eyelet, especially if there are already many things there already.
Many hobbyists use hookup wire for the ground bus between eyelets. This is more expensive than using bus wire, and will fill the space more quickly since the insulation will occupy space above the eyelet and (maybe moire psychologically than practically) make the eyelet seem full before its time. However, hookup wire may be all you have and you just want to get the amp built. Digikey and Mouser offer bus wire in many sizes, both by thickness and length.
In the Portaflex project, there is no eyelet that has more than five wires. I can see that if you combined the three eyelets feeding the splitter ground that you would have quite a junction.
Using the $33 eyelets (1/8" dia) and appropriate wire gauges for the circuit, there is usually no problem having quite a dense number of lead outs.
Most component leads are around 0.032" or so, maybe 0.047" for a filer cap lead, and the bus wire is usually #24 (solid-wire that is tinned). All of our kits and projects specify #22 hookup wire and shielded calbe is #22 or #24. I use #24 coax and 2-conductor shielded wire.
For some reason, a lot of hobbyists think that they need fat wire for high-voltage, and then buy #16 or larger wire. This is the wrong way around. High-voltage needs better insulation NOT a thicker conductor. Current in a tube circuits is a few milliamps or less, wgich is easily carried by very thin wire that is actually more difficult to work with and does not come with high-voltage insulation. There is a common very-thin wire that is solid-core and Teflon-insulated used for wire-wrapping - an old way to prototype and to construct low-voltage circuits.
TUT3 gives a list of wire gauges and their current capacities. These ratings are conservative and assume an insignificant temperature rise inside the wire caused by heating by that current. So, #22 is rated at 2A, which is high enough to feed the heater of an EL-34 or 6550 PROVIDED that is the only current being carried by this wire. TUT3 shows wiring solutions that allow all wiring in an amp to be small-gauge. You can find ratings charts where #22 can carry 90A - but this is with a temperature rise in the wire of nearly 100C !!! We do not want this in our builds.
The other thing to do is to tin the wire ends. I use stranded wire only, except for bus wire and links made from cutoff resistor leads. I twist the strands and tin it before making the connection to switch lugs, or for insertion into PCB pads or component solder lugs. The tinning should be "light" inasmuch as the solder should flow evenly over the wire and not obscure the individual strands. There should not be any "globs" or thick parts of excess solder. This tinning step helps keep each wire unitised and they will be easier to poke into an eyelet, especially if there are already many things there already.
Many hobbyists use hookup wire for the ground bus between eyelets. This is more expensive than using bus wire, and will fill the space more quickly since the insulation will occupy space above the eyelet and (maybe moire psychologically than practically) make the eyelet seem full before its time. However, hookup wire may be all you have and you just want to get the amp built. Digikey and Mouser offer bus wire in many sizes, both by thickness and length.
In the Portaflex project, there is no eyelet that has more than five wires. I can see that if you combined the three eyelets feeding the splitter ground that you would have quite a junction.
