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PostPosted: 25 Mar 2010, 21:00 
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Major costs will be the transformers. Have you decided on a brand? Tubes may be pricey too depending on which you want.

As for a stereo build, it will be very heavy and sourcing a single power transformer may be tough - depending on which tubes you run with.

As for boards, I may have an extra set from the group buy. I also will not be using my Altronics phase splitter transformers from the group buy as I recently purchased a pair from Sowter.

Cheers and welcome to the forum.

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PostPosted: 05 Jun 2010, 17:32 
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Location: Chillicothe, Ohio
A few shots of my progress. My retirement is in full swing now, so I have more time to spend on my projects. The first picture is most representative of the colors. The others are kinda washed out due to my poor photography skills. I painted the top plate gray hammertone and the rest of the panels, black hammertone, which actually appears as a dark gray. I'm considering painting the bell ends on the Edcors. The blue just doesn't do it for me with the gray and black.

I fabricated the chassis using raw aluminum panels and sheets I got from Speedy Metals. It is very sturdy with 3/16" sides and front, and 1/8" top, bottom and back. I used 3/4" square aluminum in the corners to anchor the panels to with 8-32 button head allen screws on sides, and 6-32 button heads elsewhere. Tops and bottoms of these square corner pieces are drilled and tapped and used to connect the top and bottom plates. Lots and lots of time spent drilling and tapping, but it is well worth the time and effort. I'm very pleased with this after my fiasco with the Hammond enclosure. Also opted for the Sowter phase splitters since my original plan.

Image

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Got some wiring to do and should be ready to test soon.

Cheers,
Greg


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PostPosted: 06 Jun 2010, 10:37 
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Looking good Greg. I like the Edcor blue with black, but likewise, perhaps not so much with the grey.

I went with a pair of the sowter units as well. I recently got all the passive parts, but I still need enclosures, chokes and input tubes.

Looks like you have plenty of room now. What are the overall dimensions of your enclosure?
Cheers

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PostPosted: 06 Jun 2010, 13:39 
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Hey Gio!

The enclosures are 14"W x 12"D x 4"H. As I mentioned, the aluminum is from Speedy Metals. I've been doing quite a bit of business with them and they will cut any pieces to spec on CNC equipment. So all cuts are precise and square. All I needed to do was determine where to drill holes and then prep for painting. I'm very happy with the results. I have several hours involved in the chassis, of course, but probably about $80 total invested. No way one could buy such chassis for anywhere near that.

Also, I am going to add a bright blue LED dead center in the front panel. Getting kind of anxious now to finish these up and move on to something else.

Cheers,
Greg


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PostPosted: 07 Jun 2010, 12:43 
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Hi Greg, I'm gonna have to go with an aluminum Hammond chassis.

I just looked back at your Millett UniAmp Chassis / Enclosure Considerations post and wanted to confirm the height requirement. Will 3" thick be enough or should I be looking to get 4"?

It looks like I will have to get the 17" x 10". You noted that the top may look a little bare, so now I am thinking maybe go with the enclosed choke and mount it on top. What do you think?

Cheers

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PostPosted: 07 Jun 2010, 14:36 
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Gio,

I could have used a 3" height just fine. The open frame choke is 2 1/2" high, and the pcb is about 2 1/4", which includes 3/8" standoffs and the electrolytic caps. I agree with the enclosed choke idea if you go to 17" x 10".

Cheers,
Greg


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PostPosted: 07 Jun 2010, 22:53 
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Thanks for the dimensions Greg.

Just spotted these new painted and walnut hammond chassis today. They look pretty good and I think I will try them out.

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PostPosted: 08 Jun 2010, 19:39 
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Those look nice, Gio! Hopefully the prices will be attractive.

Cheers,
Greg


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PostPosted: 10 Jun 2010, 14:09 
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Got my first UniAmp wired up, and checked and double checked all connections. When I was satisfied all was in order, I brought it up on my variac. At about 50V, both power transformer connections to the rectifier tube started arcing at the solder pads on the pcb. These are marked RECT P1 and RECT P2. It appeared they were shorting to the ground plane. At first I just removed the transformer leads and connected them directly to the appropriate tube socket pins, but same issue and I realized voltage was still running back to the solder pad through the pcb trace. I removed the pcb from the chassis and cut the traces in two. Problem solved and amp has been playing nicely for about 1 hour. Later, after the second amp is finished, I'll comment on sound quality etc., when they are connected to decent speakers. For now amp is connected to junk speaker, and has old tubes installed.

Everyone who is using these pcbs should take note of this. I inspected the few that I have remaining, and they look fine, and I've got no negative comments from anyone who bought these in the group buy, but everyone be aware and watch for this

Cheers,
Greg


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PostPosted: 10 Jun 2010, 21:51 
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:hot:
Did you cut the traces at the socket pin?

What did the problem appear to be?

Cheers

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