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Vacuum tube amp build
RotarySMP:
Very cool project. I built a MADAMP A15 kit a few years ago. Sounds great. I like how you let your son live his design impulses. Understatement come later :)
Mark
Alphawolf45:
Tube type electronics was my obsession for at least 20 years. Upstairs in my machine shop I have a 20 by 20 foot room stacked with stuff and a 20 by 20 foot deck up there holding some overflow..And my house is full.... I sold 75,000 tubes on ebay years ago just to get rid of them......However , despite all that and more , I never built anything , only repaired... Weldingrod, you do neat work and you don't know how much I respect that. :) :)
WeldingRod:
I've finally got progress to report!
We powered up and got glowing tubes! :beer:
However... only the tiniest hint of sound. :zap:
After running the ground wire to the front panel and knobs (d'oh), we got... not much of anything.
More careful inspection and thinking. Measuring (what a thought). Wait, that 470 Ohm 5 Watt resistor should have actual voltage across it! Oops, I ran the red lead of the output transformer to ground, not high voltage. :doh:
Ok, after fixing THAT, I powered up and was greeted by...wait for it... LOUD oscillation. Scream. :bang:
More looking, poking, fiddling. Thinking. And, most crucially, surfing the web. I got a couple of ideas, and disconnected the feedback. The oscillation went away! Of course, all the sound went away too, so not totally optimal. But, it got me suspicious that the output transformer phasing might be backwards. Sure enough, swapping leads led to actual functionality! :)
I do have to admit that the photo of a guitar plugged in is from when it wasn't really working... Gotta get Carl and the guitar back out to the shop.
I'm still fiddling with the meter; Carl wants it to move when things are playing. It doesn't actually need to display anything useful or quantitative, just look cool! Thus, I hooked it across said power resistor. With some fiddling and capacitors, I got something that bounces nicely with the beat. However, when I bought the final parts and, um, added a couple of things... it didn't work. More fiddling.
WeldingRod:
Progress! We cut cellulose composite material (plywood) yesterday, glued up, and routed. Carl has been filling and sanding while I girl scouted (I'm the troop leader, many dimensions of weird).
It's just a test fit, still needs grill cloth and Tollex.
Sent from my SAMSUNG-SM-G891A using Tapatalk
WeldingRod:
Almost done! Sunday was "learn to Tollex" day! I'm frankly amazed at how well and easily it went, especially after reading the instructions that said "and don't start with fancy snakeskin; you want black!" Many hours of gluing later... Lots of fiddly cuts and masking where the contact cement gets painted. Another skill to add to the set. Water based contact cement is pretty cool stuff!
:headbang:
And a beauty shot! There's a bar behind the grill and grill cloth that has an LED strip shining on the cone. Yes, the control panel is glowing too.
It still needs amp corners, feet, and, maybe, actual labels on the controls ;-)
The meter jumps around nicely when he's playing too. I am, as they say in Britain, chuffed! And I actually got some smiles out of my teenager!
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