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Six Year SSE Project Nearing Completion

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Hey everyone,
On 4/14/2014 I purchased a Tubelab SSE board from George.
Well, I've finally gathered every last part I need to to finish this project!

For me, by far the biggest hurdle - so far - was the chassis. My hobby budget doesn't permit a custom fabricated job; I had to go with a $36 Hammond and do all the cutting myself. Using a stepped bit, various files, and sandpaper I ended up with a chassis I'm happy with. I intend to paint it tomorrow with self-etching primer and textured paint (too many imperfections for a smooth, gloss finish).

Here are a couple of photos...
 

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Rustoleum self-etching primer and textured paint.

I bought a piece of oak at Lowe's for the sides. I still need to bevel the edges with a router and stain them.

Lots of little imperfections in the finish - spray cans always spatter for me - but, it's good enough!
 

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Thanks Duke58. No, I assembled the board back in 2014. I just got around to ordering the Edcors last summer, and bought the Hammond chassis a few months ago.

A couple of moves, new jobs, and life priority changes have caused me to shelve this project more than once over the last six years.

The next step, that I'll work on today, is removing the thick blue paint from some of the Edcore mounting tabs.

So, here's an important question: Is it better to have all four mounting tabs on each of the three transformers (12 total points) make a bare metal contact with the chassis, or, should I just ground one tab on each of the transformers to the chassis?

Thanks!
David
 
The next step, that I'll work on today, is removing the thick blue paint from some of the Edcore mounting tabs.

So, here's an important question: Is it better to have all four mounting tabs on each of the three transformers (12 total points) make a bare metal contact with the chassis, or, should I just ground one tab on each of the transformers to the chassis?



Use tooth washers.

I never scraped any paint from my Edcors mounting tabs.
I use tooth washers at the top over the tabs and at the bottom under the
chassis plate. After this I thoroughly check to ensure continuity from the
laminations to the chassis and to the ground pin on the power input IEC.
 
Yes, however the laminations are mostly coated so you'll have to probe until the
probe touches a spot where there is bare metal, if not just make a small scratch to
get a bare metal contact. Of course I'm sure you already understand that the IEC
ground pin must be connected to your star ground or other suitable ground point
on the chassis.
 
Thanks both of you! Very much appreciated. Yes, I am following the Tubelab grounding scheme.

With my poor eyesight and slightly shaky hands, soldering this sub-assembly was a challenge. But, everything checks out with the multimeter.

I just used shielded cable from an old RCA interconnect. I designed my chassis layout so that my signal wires are as short as I could make them within reason.
 

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Looking great so far!

I am hoping to complete my SSE build soon, and I had the same question about the transformer tabs. Seems to me metal-to-metal contact is required so the transformer chassis are grounded to the top plate (and top plate is connected to EIC ground) for safety reasons. The tooth washers apparently accomplish this by biting through the paint. I hadn't thought of that, so thanks to spendorite for that!
 
Like most of us, I've got plenty of stay-at-home time on my hands, so I went ahead and removed the paint from the tabs.

I also decided it couldn't hurt to allow a bit of ventilation in the chassis, so I drilled holes in both sides for what it's worth. Now I can run the router over the edges and stain/seal the wood.
 

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Nice. The holes in the sides will help a bit. It looks like there is a bit of a gap between each tube socket and the top plate, so the "chimney effect" from the tubes (and the convective current of heat rising from the board components under the top plate) will tend to create air flow through the gaps. The resulting slight negative pressure will draw fresh air into the chassis through any holes. To enhance this effect, some builders drill a pattern of holes around each tube socket. An extreme application of this principal is described by Morgan Jones, in his book "Building Valve Amplifiers":

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Thanks cogitech!

Yes, when I drilled the holes for the tube sockets I wasn't sure what length of hex standoffs I would be using to mount the board, so I made the holes large enough for the sockets to clear the chassis in case they protruded out of the top (or, if the tube bases needed to extend into the chassis). I ended up using 1/2" standoffs and the sockets sit just barely beneath the chassis. So, as you said, this does allow enough space for air to flow up and out which should pull fresh air in through the holes... a convection system as you aptly described it!

The MakerSpace where I work is obviously closed for now, but if I ever do another chassis in the future I will use their laser to cut radial slots around the socket holes, as some folks do. I think that effect looks great.

David
 
I'm just doing small stages at a time, so as not to get ahead of myself.

It was easier to wire up the star ground leads before I mount the board or transformers.

The ground is on one of the choke mounting bolts. After I install the choke I'll go back and put more solder on the nut and eyelet. I might add a piece of heat-shrink tubing for stress relief, too.

The four wires are from: one of the RCA ground tabs, the IEC ground lug, and the two loose wires will attach to the black speaker-terminal binding posts along with the two appropriate OPT wires.

I'm pretty sure I haven't missed anything else that needs to be attached to the star ground. But, I welcome all comments and suggestions. Thanks.
 

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Hi, I have a basic question concerning the OPT hookup for triode mode without CFB.

Looking at the Tubelab diagram I've attached, do I jumper the plate wire (blue on my Edcors) into the UL connector?

Also, do I jumper the CFB connectors, too?

I'm just not 100% certain I'm reading the diagram correctly. If anyone has a photo of an actual board wired this way that would be great.

Thanks!
 

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