Clementine number ?

sweet & juicy SE amp for 1626 Darlings and the 6L6 family

Clementine number ?

Postby Ty_Bower » Fri Sep 16, 2011 7:29 pm

Someone once told me the key to making progress was to accomplish a little bit every day. I think today was a pretty good day.

I got a nice package in the mail from Bolt Depot. It's full of stainless steel #6 and #8 hardware.
Image

I've oiled the woodwork. Watco's takes forever to dry. (sick)
Image

Best of all, I've completely stuffed the board. (Note to the Brits: In the Colonies, that's the exact opposite of what you're thinking.) I've used some fancy boutique parts, such as the Wima coupling caps and the premium audio grade Nichicons for the bypass caps. I've also got carbon composition resistors at the grid stoppers, just because I drank that Kool-Aid. Finally, on the other side I've substituted fast recovery UF4007 diodes and Schottky diodes for D1 through D4. I'm curious to see how the Schottky diodes affect the heater supply. I did use a 3.75 ohm power resistor for R26, as it was the smallest power resistor I had around. I'm concerned it will drop too much, but time will tell.
Image

If the weather is still nice tomorrow, I should be able to get the chassis plate primed and painted. After that, it won't be long before I'm making music. (y)
"It's a different experience; the noise occlusion, crisp, clear sound, and defined powerful bass. Strong bass does not corrupt the higher frequencies, giving a very different overall feel of the sound, one that is, in my opinion, quite unique."
User avatar
Ty_Bower
KT88
 
Posts: 1492
Joined: Wed Mar 21, 2007 2:50 pm
Location: Newark, DE

Postby Ty_Bower » Fri Sep 16, 2011 8:13 pm

I needed to know whether or not the heater voltages would be OK, so I connected the Edcor XPWR-177 and took a few measurements.

My line voltage is 123.5 VAC.
B+ with no load (no tubes installed) is 295 VDC.
Heater voltage with no load is 18.25 VDC.

I installed a set of tubes.
Image

Heater voltage is now 11.45 VDC. Do you think that is a bit too low, or is it within acceptable limits? What is the specified heater voltage anyway? Is it 12 VDC, or 12.6 VDC? I'm a good ten percent low, aren't I? I suppose I could parallel another 3.75 ohm resistor along with the first one, and cut the voltage drop across those resistors in half.

I checked again with a shorting wire across R26, and I saw 13.2 VDC at the heaters. I guess that's a bit more than I want.
"It's a different experience; the noise occlusion, crisp, clear sound, and defined powerful bass. Strong bass does not corrupt the higher frequencies, giving a very different overall feel of the sound, one that is, in my opinion, quite unique."
User avatar
Ty_Bower
KT88
 
Posts: 1492
Joined: Wed Mar 21, 2007 2:50 pm
Location: Newark, DE

Postby Shannon Parks » Sat Sep 17, 2011 4:45 am

Ty_Bower wrote:I checked again with a shorting wire across R26, and I saw 13.2 VDC at the heaters. I guess that's a bit more than I want.


That is exactly what I have done. A 1 ohm would get you perfect, but you are within +/-5% which is A-OK. Looking good!

Shannon
User avatar
Shannon Parks
Site Admin
 
Posts: 3762
Joined: Tue Mar 18, 2003 5:40 pm
Location: Poulsbo, Washington

Postby Ty_Bower » Sat Sep 17, 2011 12:54 pm

I dunno. Those clouds don't look so good. At least it isn't raining right now. Oh well, let's see what happens.
Image

Primed.
Image

Painted.
Image

Now it's like watching paint dry. :)) I wonder how long I should waited before starting to put it all together.
"It's a different experience; the noise occlusion, crisp, clear sound, and defined powerful bass. Strong bass does not corrupt the higher frequencies, giving a very different overall feel of the sound, one that is, in my opinion, quite unique."
User avatar
Ty_Bower
KT88
 
Posts: 1492
Joined: Wed Mar 21, 2007 2:50 pm
Location: Newark, DE

Postby 20to20 » Sat Sep 17, 2011 1:07 pm

Ty_Bower wrote:I dunno. Those clouds don't look so good. At least it isn't raining right now. Oh well, let's see what happens.
Image

Primed.
Image

Painted.
Image

Now it's like watching paint dry. :)) I wonder how long I should waited before starting to put it all together.


Pull out your Parsley, Sage, Rosemary and Thyme... Bake the chassis while you listen to the LP.
Headed for Tishomingo to sing in a can...
User avatar
20to20
KT88
 
Posts: 566
Joined: Wed Apr 21, 2010 1:48 pm
Location: W-S, NC

Postby Ty_Bower » Sat Sep 17, 2011 6:13 pm

I guess it's dry enough. It stills feels a little plasticky, but rattle can takes weeks to fully harden. I'm not 100% sure about how the blonde makes me feel. Maybe it'll grow on me after a while. At least I've graduated from the framing lumber.
Image

Wow, that's a lot of extra lead on those Edcors. I'll need to trim those down to something manageable. Here's a tip for the GXSE10 - #8 hardware is a really tight fit into those tiny mounting ears. I would have used #6, but all my #6 is only long enough for the circuit board.
Image

It almost looks like it will be an amp some day. Maybe tomorrow I'll finish the wiring underneath. I can't wait to fire it up and take a listen.
Image
"It's a different experience; the noise occlusion, crisp, clear sound, and defined powerful bass. Strong bass does not corrupt the higher frequencies, giving a very different overall feel of the sound, one that is, in my opinion, quite unique."
User avatar
Ty_Bower
KT88
 
Posts: 1492
Joined: Wed Mar 21, 2007 2:50 pm
Location: Newark, DE

Postby Shannon Parks » Sun Sep 18, 2011 4:47 am

Looks cute as a button. Can I say that about about a tube amp? It is a Darling after all. ;)

Keep an eye on your initial biasing. I presume your B+ will sag nicely into range and you'll be in fat city.

Shannon
User avatar
Shannon Parks
Site Admin
 
Posts: 3762
Joined: Tue Mar 18, 2003 5:40 pm
Location: Poulsbo, Washington

Postby Ty_Bower » Sun Sep 18, 2011 8:31 pm

Well, I took a shortcut and skipped the volume pot. I'll need to go back and add it in later. I'll just use my usual preamp in the meantime, and besides I don't have the right knob for it anyway.

The heaters came in at 11.8 VDC after I paralleled another 3.75 ohm resistor with the first. That's 6.5% low, but oh well. I'll just say I did that on purpose to make the tubes have a long life.

B+ is right at 243 VDC. Anode voltage is 239 VDC. I did use the "big" 10H Triad C-7X choke. It has a 270 ohm DC resistance, so it drops about ten extra volts compared to a C354. Idle current came in at 26.2 mA for one side, and 24.9 for the other. That's 5.6 watts and 5.3 watts plate dissipation. What are these guys rated, anyway?

I discovered my rattle-can paint job scratches off aluminum real easy. I torqued one of the screws just every so slightly, and the paint came right off. Bummer. Maybe it would have fared better had I waited a couple weeks for the paint to fully cure? Maybe I should just stick with power coating.

I'll try to get some more photos soon, as well as my listening impressions.
"It's a different experience; the noise occlusion, crisp, clear sound, and defined powerful bass. Strong bass does not corrupt the higher frequencies, giving a very different overall feel of the sound, one that is, in my opinion, quite unique."
User avatar
Ty_Bower
KT88
 
Posts: 1492
Joined: Wed Mar 21, 2007 2:50 pm
Location: Newark, DE

There are primers, then there are primers

Postby EWBrown » Sun Sep 18, 2011 10:31 pm

Depends on the primer you used, aluminum can be a very tricky paint job...

The primer I have used was a light yellow-green in color and very strongly adhered to the aluminum, like a limpet mine to a ship's iron hull ;) (lol)

If I recall properly - it's been a few years and a thousand miles - this primer was called an "etching" primer, and it chemically bonded onto, and into, the aluminum. The final coat of paint would adhere, and was virtually scratch-proof, except for severe gouging or abrading into the surface

For a nearly "bulletproof" finish, powder coating IS the way to go, though beyond the scope of most home-built DIY projects. .

I've tried other "automotive" primers (usually gray or brownish in color) , which were intended for use on steel, and they didn't stick to the aluminum any better than regular "rattlecan" paint, and both of these primers (and top coats) would scratch off from the metal surface with very little effort.

Bare naked aluminum has a very thin and transparent "oxide" layer which can act almost as if it were a teflon coating :( :/

This oxide also acts as an electrical insulator, but it also pierces very easily with star or other "toothed" washers, and nuts.

/ed B
Real Radios Glow in the Dark
User avatar
EWBrown
Insulator & Iron Magnate
 
Posts: 6389
Joined: Wed Mar 19, 2003 6:03 am
Location: Now located in Clay County, NC !

Postby zippy1540 » Sun Sep 18, 2011 10:41 pm

The primer you are talking about is called Zinc Chromate. I used it during my time in the Air Force as a Corrosion Control specialist. Ed is exactly right on aluminums surface coating. Using a DA Sander on the surface then a quick wipedown with MEK and spraying it should get the primer to bond properly.
zippy1540
 
Posts: 172
Joined: Mon Mar 27, 2006 11:28 pm
Location: spokane washington

Postby Shannon Parks » Mon Sep 19, 2011 4:20 am

I have used this self etching primer:
http://duplicolor.com/products/selfEtchingPrimer/

Not a common item, but an automotive store will have it. I bought mine at a NAPA store. I'm experimenting with chromate dips and anodizing, but this is far easier and I've had excellent results.

Shannon
User avatar
Shannon Parks
Site Admin
 
Posts: 3762
Joined: Tue Mar 18, 2003 5:40 pm
Location: Poulsbo, Washington

Postby Shannon Parks » Mon Sep 19, 2011 6:17 am

Ty_Bower wrote:Idle current came in at 26.2 mA for one side, and 24.9 for the other. That's 5.6 watts and 5.3 watts plate dissipation. What are these guys rated, anyway?


They are spec'd at 5W dissipation. Looking at all the schematics for the various Darling incarnations over the years, they are always run maxed out, so you are A-OK. Mine are biased up the same. That said, with higher plate voltages and lower currents all my 1626s were prone to thermal runaway. I guess this is just a sweet spot.

Shannon
User avatar
Shannon Parks
Site Admin
 
Posts: 3762
Joined: Tue Mar 18, 2003 5:40 pm
Location: Poulsbo, Washington


Return to clementine

Who is online

Users browsing this forum: No registered users and 0 guests

cron