What is happening in those wires?

Thread Starter

Gerry Rzeppa

Joined Jun 17, 2015
170
This looks like an amazing toy for a 12yr old...
Right you are! Well, except for the "toy" part; like Coca-Cola, this is the Real Thing. The folks at the Kendrick "Build Your Own Amp Camp" have been helping kids of all ages (12 to 84) build tube guitar amps for many years:

kendrick amp camp.jpg

The Lion VII kit, in case you're wondering, is an all-tube amplifier that packs about 10 times the power as my 5-watt Banana Jack Amp.

The people at Mod Kits are also succeeding with kids. Here's a 13-year-old who built a tube amp for his 8th grade science project:

https://www.modkitsdiy.com/video/mod-102-review-chase-walker

A few years ago my 11-year-old son and I built an amp using the same Mod-102 kit as a base, but we packaged it up steampunk-style:

front.jpg guts.jpg

Tube guitar amps are great teaching tools because:
(a) they employ discrete components that are large enough to be seen and felt and examined without a microscope; and
(b) almost all the fundamental concepts and components are included in a single circuit: transformers, rectifiers, capacitors, resistors (variable and fixed), transducers, lamps, switches, magnetic pickups, AC and DC currents, high and low voltages, high and low impedances, etc, and
(c) these devices are still in widespread demand and use today; the kid can use his creations in his own band, or he can sell them on eBay (we got $576 for the amp shown above).
 
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Wolframore

Joined Jan 21, 2019
1,254
I'm sure someone likes it.... and your project is pretty cool but doesn’t look safe for kids... sorry too busy to roll my own... I have a Marshall, black star and two fender tube amps... plus a number of tube compressors (LA2A...) and preamps (Manley and Avalon). I actually like the Trident and Neve solid state stuff a little better... the last tube amp I modified had 140v plate voltage. I wouldn’t want my son plugging things in and out of those.
 
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Thread Starter

Gerry Rzeppa

Joined Jun 17, 2015
170
the last tube amp I modified had 140v plate voltage. I wouldn’t want my son plugging things in and out of those.
Perhaps it's a generational thing. When I was a kid, cars didn't even have seat belts, nobody wore a helmet to ride a bike, and any 12-year-old in the neighborhood knew how to cut the lawn, without supervision, using a power rotary mower. Most 12-year-old boys I meet today can't get a bit out of a power drill without help, and that just ain't right. Not my kid. He knows how to use all the common hand tools, several kinds of power saws (with those damn blade covers removed so you can see what you're doing), a drill press, a grinder, a wood lathe, etc; he knows how to solder with both an iron and a torch, how to weld (TIG and MIG), and how to cook his own potassium-nitrate-and-sugar rocket fuel in a pan. Almost forgot: he can shoot everything from a 9mm Glock to an AR-15. So "Don't fuss with those red wires when the thing is plugged in" is something he can (and has been able to) handle. Maybe someday I can get this guy...

https://www.artofmanliness.com/articles/23-dangerous-things-let-kids/

...to add "Build a tube guitar amp" to his list.
 

Wolframore

Joined Jan 21, 2019
1,254
Actually it is a bit of a generational thing, don’t forget to add running a metal lathe and mill to that list. And we have done pretty much everything on that list. I’m actually relieved that my son grabs the face shield and gloves when he grinds things. I don’t always follow the safety rules.

I volunteered as assistant scoutmaster and boys can still be boys. Look up fire piston... we milled a metal one and it was fun at camp.

So those caps discharge when you unplug the amp? In order to do what I do with them I have to have them plugged in and know where the voltages are when I poke around. I just don’t like those plugs. It’s too easy to unplug and accidentally touch high voltage. Have you seen those double male power lines people make and use to jump power? Again one of those things that can have dangerous consequences... I think you know... I don’t know about giving my kid something nicknamed widow maker or suicide cord.

 
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Thread Starter

Gerry Rzeppa

Joined Jun 17, 2015
170
Look up fire piston... we milled a metal one and it was fun at camp.
Those fire pistons are great -- I didn't know they existed. Thanks. They're on my bucket list now.

So those caps discharge when you unplug the amp?
Turns out they discharge in about 4 seconds (with the whole amp wired), even without a bleed resistor. Even faster then. We use a piece of 14-gauge wire to discharge caps when we're working on a standard chassis. After being surprised by the spark the first time (I intentionally didn't warn him to ensure a memorable "limbic" experience), the kid was quickly convinced of the necessity of this step. It had the same effect as when we put a popsicle stick on a hot stove burner to explain why fingers should be kept away.

In order to do what I do with them I have to have them plugged in and know where the voltages are when I poke around.
Of course. Can't check those plate voltages if the thing isn't plugged in. We use a clip on the ground side and poke around with the other probe with one hand holding the meter or behind our backs. We're not daredevils or adrenaline junkies. But we do like getting things done. But how can you line up the right tooth on a miter saw blade if you can't see it and push it around a little with your hand? Those laser guides (on inexpensive tools) are crap.

I don’t know about giving my kid something nicknamed widow maker or suicide cord.
Rest easy. Never made a widow maker, and (probably) never will. I don't like having those exposed prongs (with the significantly different surface charges) within an inch of each other either. I got a shock once, in fact, trying to plug a cord in the wall behind a big piece of furniture when my thumb slipped over the edge of the halfway-inserted plug. But the Banana Jack Amp is different -- there's only one prong on the end of the wire, which is pretty much the same as a wire (with no plugs) in a standard chassis that has been attached at one end and is about to be soldered at the other. In both cases, safety is in proper procedure: unplug, drain caps, go to work.

Is that you in the video? The guy kind of looks like the avatar on your posts, minus the cigar.[/QUOTE]
 
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