amp out of tube radio

[shoggoth]

More work done this weekend, and I've ordered waterslide decals for the power amp chassis. I'm going to clearcoat over the tooling marks and hope it levels enough so that the decal looks decent.

Here's the radio chassis with the relay board and volume controls wired up (except for relay power). Wish there was room inside for the relays, this is a very silly way to wire up the amp. The volume control is mounted where the tuning capacitor knob used to be.

[img682]http://i234.photobucket.com/albums/ee25 ... b047d0.jpg[/img]

Here's the preamp and power amp. It's cramped in there, and the tube sockets are in totally inconvenient places. The heaters are DC and signal wires are mostly shielded, so hopefully it's not too noisy. I still need to run the heater power wires.

[img682]http://i234.photobucket.com/albums/ee25 ... 7ff11d.jpg[/img]

Here's the power chassis, with the transformer and 90v power supply. The preamp is at 90v and the power amp at 75v, so there's a lot of filtering going on in here before it even hits the preamp. I still need to put the regulated 7.5v supply together for the heaters, relays, and volume/gain displays.

[img682]http://i234.photobucket.com/albums/ee25 ... 55d99b.jpg[/img]

[thereminator]

This conversion is a simple vandalism.

[shoggoth]

If it's a comment on build quality, hey, first tube amp.

If it's a comment on preserving a $20 radio, they are in fact so common that you can buy them for $20 - cheap enough that you can stuff your garage with them and build a museum if you're so inclined.

[Cygnus X1]

I've done a few of these with RCA's, Crosley, and Zenith radios.
I usually gut them out and build either 5C1 or 5F1 circuits into a fresh chassis and either reclaimed or new 8" speakers.
Nothing wrong IMO in these conversions.
SOME tabletops are too fine to convert though.
I have a couple Zenith's that will go forth as designed originally.

[Cygnus X1]

Here's my hijack:

[img:717:538]http://imageshack.us/a/img253/1185/rcaradiator5f1.jpg[/img]

[img:515:775]http://imageshack.us/a/img838/2294/rca5 ... ntback.jpg[/img]

[img:473:458]http://imageshack.us/a/img35/9140/crosleychamp2.jpg[/img]

Some guts:

[img:740:460]http://imageshack.us/a/img109/7328/rcachampgut1.jpg[/img]

[shoggoth]

Very cool, Cygnus!

So I printed & applied the water-slide decal to label all the junk on the power supply chassis. I put the input jack in their as well, because it's a convenient spot to mount it. It's well away from the power stuff and will have a shielded cable run so hopefully won't add noise.

I had sprayed 5 coats of clear-coat over the label, and then soaked it in water for 30 seconds before applying. That may have been too long, because when I went to take it off it rolled up into a straw-sized tube. I flattened it out, but the clear coat is all crackly now. You have to hold it at a certain angle to see the crackling, but still annoying. Maybe the next few coats of clear coat after it's applied will melt the existing stuff and clear out the cracks? Wild hopes, probably it will just make them stand out all the more.

The clear coat over the aluminum filled in all the dings, so the decal went on great, but also highlighted the tooling marks pretty well so every scratch is especially visible. I just wanted to label the existing aluminum though and have it not look completely lousy, so overall I'm good with the results.

You can see a little tiny speck of blue sponge in there as well under the 0.1A. Whoops... chassis sponges are a vital part of the tone though, so it can only help.

[img768]http://i234.photobucket.com/albums/ee25 ... a68a64.jpg[/img]

[Structo]

Nice looking chassis!

The secret to doing waterslide decals is the surface should be clean, dry and smooth.

You don't want to soak the decal too long or it will take the glue off the back.

I leave my decals in warm water for about 10 seconds, then take it out and lay it on a paper towel to absorb excess water.

Then place the decal where you want it.
Some guys like to use a Decal Set solution but for flat surfaces it really isn't necessary.
Use a Q tip to lightly smooth out the decal or to remove air bubbles.
Then let the decals dry overnight.

If you desire to clear coat over them, the secret is to spray very light misting coats over the decals.
Two or three light misting coats should lock them down.
Let those dry well.

Then you can apply a few wetter coats but don't apply it too heavy or it will run, or worse, wrinkle the decals.

I use nitro lacquer over mine and haven't really had any issues as long as I do the light coats at first.

[shoggoth]

It lives! Kind of...

The plate voltages are all a bit high. They were very very high when I mistakenly used the center-tap rectification formula instead of the bridge formula. Whoops.

The filament voltages are all low. The 7.5v regulator doesn't like the center-tap-rectified 12.6v, and is only putting out around 6v. The math says 8.9v rectified, and data sheet wants 9.5v. Should've read that more carefully... whoops again.

One of my RF pentodes is bad. I suppose the fact the base had turned green from corrosion should've been a hint. So the high-gain channel isn't working yet.

The "clean" channel works. But the heptode is picking up some oscillation, probably 60hz or 120hz from the power supply, and being a heptode, its modulating the guitar input with it. So I've got a ring modulator / weird tremolo thing going on.

And finally, it hums like a bastard, volume control has no effect on the hum. I'll have to figure that one out. It might go away once I get a lower voltage regulator for the heaters - I can't imagine underpowering it is doing much for clean regulation.

At 1/8w, turned up to max its at loud conversation level. So perfect for a bedroom amp, when I get it finished.

[fullwood]

Nice looking chassis!

The secret to doing waterslide decals is the surface should be clean, dry and smooth.

You don't want to soak the decal too long or it will take the glue off the back.

I leave my decals in warm water for about 10 seconds, then take it out and lay it on a paper towel to absorb excess water.

Then place the decal where you want it.
Some guys like to use a Decal Set solution but for flat surfaces it really isn't necessary.
Use a Q tip to lightly smooth out the decal or to remove air bubbles.
Then let the decals dry overnight.

If you desire to clear coat over them, the secret is to spray very light misting coats over the decals.
Two or three light misting coats should lock them down.
Let those dry well.

Then you can apply a few wetter coats but don't apply it too heavy or it will run, or worse, wrinkle the decals.

I use nitro lacquer over mine and haven't really had any issues as long as I do the light coats at first.

Thats how I do mine. I only use the Decal Set when I am putting decals on wood. Even then, I make sure the surface is sanded as smooth as I can get it. The secret with clearcoat is LIGHT coats. I polish between coats sometimes, but only lightly. Great job on the build, recycling in action!

[tsutt]

So where do you get these water slide decals or how do you make them?

[shoggoth]

I bought mine from Amazon: http://www.amazon.com/gp/product/B0013P ... UTF8&psc=1

Those are for inkjet printers. Laser printers use different decals.

My big problem was leaving the decal in the water too long, so most of the glue dissolved, thing rolled up like a cigar, and it looks worse the more time goes by now. No biggie, I'll just get one of those laser engraved plates done at some point, and now I know what not to do when I try it next time. Have to get the amp working first though.

Speaking of which, here's a clip of the hum and the modulation recorded on an iPhone. Dumble's going to be all over this tone.

[Reeltarded]

I use two wet sponges. I dip the sheet then lay it on a sponge, put the other sponge on top and wait about 60 seconds, check that it is sliding and then apply it to the area using the wetted backing as a tool to press out bubbles from the middle. After the first one I rub the last piece of backing on the next area to get a decal as that promotes stickydom.

[FUCHSAUDIO]

I started one with an SMPS, a push pull 6SN7 output tube for about 2-watts, 2 12AX7 tubes...with a Jensen 5" guitar speaker rear mounted on a metal grille... http://www.tubesandmore.com/products/P-A-MOD5-30. Gain, tone, volume. Debating on whether to try adding digital reverb for fun. Gut pics as things proceed....should run on a Godlyke or Visual Sound 9-V wall supply....and sit nicely in my den....

[Structo]

I use two wet sponges. I dip the sheet then lay it on a sponge, put the other sponge on top and wait about 60 seconds, check that it is sliding and then apply it to the area using the wetted backing as a tool to press out bubbles from the middle. After the first one I rub the last piece of backing on the next area to get a decal as that promotes stickydom.

That is some good info Miles.

Probably keeps the paper from rolling up too.

I'll have to try that way next time.

I probably leave my decal in luke warm water for 10 seconds or so then lay it on a paper towel for a few more seconds to let it soak up the water so the decal will slide.

tsutt, you can buy waterslide decal paper many places, from hobby shops to online.

If you print with a inkjet printer, you must use inkjet paper.
AND, you must seal the ink with a clear coat so the ink doesn't run when put in water.
2-3 light coats of clear allowing it to dry between coats is usually sufficient.

From what I understand, laser print ink is not water soluble so that is a plus.
Laser decal paper is available too.

If you want to bury the decals in clear coat so that the surface of the control panel is flat and smooth, you have to spray 6-8 or more coats of clear, then carefully wet sand and polish like you would for a guitar finish.

You can use acrylic clear or nitro clear lacquer but which ever you use, be sure to apply light coats bordering on them looking dry.

Nitro lacquer is good to use because it melts into the previous coat so there isn't that critical window of time between coats.

Don't worry about any orange peel, (looks like the surface of an orange) because it will be wet sanded out.

I would start with 1000 grit black wet sand paper, and move to 1500, then 2000.
Change the grit when the previous scratches are gone.
Use a light touch as the paper will cut quickly.

Then use an automotive polishing compound such as 3M Finesse or similar to polish the panel to a high gloss.

If you want a satin or semi-gloss look you will have to use a satin lacquer and spray pretty perfectly on the last couple coats.

I have used this decal paper before and it works fine.

http://www.belldecal.com/inkjet_decals.html

Or if you have a well stocked hobby store nearby, they usually carry the Testers brand waterslide paper.

[Reeltarded]

Until they changed the order of application you might notice that Fender guitars with poly finishes still have lacquer overspray to lock in the decals.

Andy, that Delco issa badass!