Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: goldteethkeith on October 09, 2022, 10:41:02 am
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I know this is a really beginner question, but I'm planning a 5e3 build and I want to do it from scratch instead of a kit. I'm using part lists from premade kits to figure out what I need, but when it comes to wire they usually describe the amount as "plenty" or "more than you need". I'm thinking 15ft 20awg for hookups and 15ft 18awg for the filament line
https://imgur.com/a/A4n0SBU (https://imgur.com/a/A4n0SBU)
This is the diagram I made that I'm going to work off, too. I'd appreciate anyone taking the time to give it a look and let me know if it's alright! Anything different than a stock 5e3 comes from Rob Robinettes page, but since I put it all together myself theres a chance I did something wrong.
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You WANT multiple colors. That usually leads you to having more wire in hand than any one amplifier can need.
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... I'd appreciate anyone taking the time to give it a look and let me know if it's alright! ...
See the 4.7kΩ resistor in the power supply? You might want to order a 10kΩ, 15kΩ as well.
You might not need to resistors, but if your PT voltage winds up being too high, they can help you tame 6V6 plate current by knocking down the screens volts some.
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So, couple of points:
If this is your first build, consider using Doug Hoffman's 5E3 "kit." It is not a complete kit, so yeah, you're going to be doing some sourcing, but it really helps to have some of the basics taken care of. His turret boards are simply the best you can get.
Don't use 18AWG wire for your heaters. It is not necessary -- your heater circuit is going to carry about 2A for all four tubes. The ampacity of 22AWG wire is 7A for chassis wiring (ie, way more than enough), and 16A for 18AWG (eg, massive overkill) . . . 22AWG wire is far easier to use than 18. Even 20AWG is a big improvement over 18. Your fingers will tell you.
Yes, I used 18AWG heater wire in my first build. Never again.
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You want some heater filament wire (about 4 feet) - , some High-Tension connection wire (about 3 feet), some signal wire (about 3 feet). I prefer single strand solid core wire for all these because it stays where you put it (YMMV). Warning - too much flexing/re-bending of single strand solid core wire is bad.
And some stranded shielded cable ('single strand') (about 18") for the sensitive signal wire.
Also handy to also get some solid-core 12-16 gauge steel wire (about 10' length max) for a ground buss.
You also want an IEC jug cord socket if you're planning a head build (or, if you're going to run a power cable straight through the chassis - a chassis cable strain relief clamp), as well as a handful of ring terminals (the crimping type) and some bolts and matching nyloc nuts for various direct-to-chassis connections.
You'll also want some rubber grommets for 1/4" or 1/2" diameter holes (for running transformer leads through the back of the chassis
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...get some solid-core 12-16 gauge steel wire (about 10' length max) for a ground buss....
Whoah? Steel is hard to solder with rosin flux. (Acid or borax may cut it but is hell on copper.)
I've always just taken scraps of house-wire and peeled-out the copper.
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Doug has a BOM for his 5E3 kit on this site. It has wire lengths & all the components. It lists 18 gauge green for the heaters - but I agree that its overkill and hard to work with. I like the waxed cloth covered 22 solid core wire. But others like other wire - go figure.
I also often use 14 awg bare copper scraps for bus wire - but also have followed Sluckey's suggestion and used galvy electric fence wire - seems to solder up well.
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> galvy electric fence wire -
Unless you already keep goats.... what is the difference #11 iron or #18 copper?
(Steel is ~about~ 7 times the resistance of copper, so copper 0.38 the diameter has about the same resistance as steel.)
You may be right about Zinc being solderable. (I rarely try because Metal fume fever (https://en.wikipedia.org/wiki/Metal_fume_fever), tho this is more about welders and may not be acute in a quick solder.)
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Long time ago I used 14AWG copper for ground buss. I would pre-tin a 6' length to make it take solder faster. About 10 years ago I switched over to 17AWG steel electric fence wire because it is stiffer, looks better IMO, solders easily when using flux, and I have a 1/4 mile spool in my shop.
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I have a 1/4 mile spool in my shop.
Time to buy PRR's goats.
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You don't need 18AWG wire for the filament string - it's overkill in that amp. 20AWG is more than sufficient. Use 22AWG for the rest of the wiring.
--Pete