Another Simple SE builder

[Ty_Bower]

There's been some activity around here lately with people building out George's Simple SE board. I recently received one, and am hoping to build it out over the summer. I'm still somewhat in the planning / ordering stage right now.

I'd like to be able to run some old Coke bottle 6L6GA tubes, but I also would like to pop in some EH 6CA7 fat bottles and run them a little harder. I think I've decided to go with one of the 720~750 VCT power transformers, and just mount a switch on the first cap after the rectifier tube. I can switch between a cap input and a choke input power supply filter. If I've done the math correctly, I think I'll end up with around 450V B+ with the cap input, and just over 300V B+ with the choke input. I'm thinking either the Hammond 374BX (doesn't buzz?) or the Allied 6K7VG (inexpensive) is the way to go.

The amp I built last summer used a 1/8" aluminum top plate with a 2x4 wooden box frame. Everything was mounted in the aluminum. It was pretty easy for me to construct, even with my limited machining and woodworking skills.



I still have a piece of that aluminum plate left, but it's a bit on the small side - about 9" x 14". I think I can squeeze everything on. I have a layout which I designed using Visio. The only piece which doesn't fit is the Triad choke. I'm hoping I can find some spare room somewhere on the side of the box frame, and just use wood screws to mount it there. I think my other option might be to mount it directly beneath the power transformer (PT on top of chassis, choke underneath). My concern is that the cores of the two would necessarily be parallel to each other, rather than the preferred (?) ninety degree angle. If you'd like to look at my chassis layout, it's attached as a PDF file. I'd appreciate any criticism.

I've already received the board from George (thank you!) and ordered most of the parts from Mouser. I even got all the fiddly bits, like the switches and binding posts and RCA jacks from Mouser. If anyone is interested in my (importable) Bill of Materials, I'd be happy to share it with you. I ordered the 500V caps from DigiKey, since Mouser doesn't really stock anything suitable. I already have all the tubes, and I got a pair of the Transcendar OT from Gery.

George - the next time you have a run of these boards made, please have them drill a hole through the PCB directly in the center of each tube. It would make it a lot easier to use the board as a template for chassis drilling.

[ciagon]

I am dealing with the same issues of trying to layout the board and get the positions right for the holes. Does anyone have measurements for the center of the tube holes on the SimpleSE board? I already soldered my components so it is hard to measure them accurately.

[whitelabrat]

If ya'll haven't stuffed your boards yet, plop it on a photocopier make a copy. Just be sure the copier doesn't change the scale of the copy. Makes for a great template.

[Ty_Bower]

Here's the dimensions I used. I just eyeballed it with a ruler, so check it for yourself before you make any holes.

[ciagon]

Awesome, thanks!

[Ty_Bower]

Originally posted by ciagon
Does anyone have measurements for the center of the tube holes on the SimpleSE board? I already soldered my components so it is hard to measure them accurately.

Here's a hint for the next "PCB under chassis" amp you build: Only solder one leg of each tube socket. Then cut your chassis' top plate, and mount the board. Now you can wiggle each socket until they line up perfectly with the chassis holes. When they're aligned to your satisfaction, solder the remaining legs on each socket.

Or just cut the chassis holes plenty big so there's no chance of missing...

[Ty_Bower]

I'm very slow to build. Sorry.

I've acquired all the glass, iron, and parts. Only thing I might be missing now is a few pieces of wood to build a box frame. Oh, and the finishing. I'm missing that too.

Here's my plan. Wood box frame, aluminum top plate chassis punched for mounting the board underneath. I've got the layout done in Visio. I think it's going to look something like this when it's done:


Aluminum plate and wood. There will be another piece of wood along the front and back, too.


Add a paper template on top for the drill guide.


Power transformer goes here.


Filter choke will hide under the chassis, directly beneath the PT. It gets screwed to the wood frame.


Populated Simple SE board goes on the left, under the chassis using 1/2" standoffs.


Transcendar output transformers sit up front. Binding posts will sit on the far right.


A couple of power tubes propped up in their approximate locations to give a feel for the finished amp.

Any recommendations before I start drilling?

[dubdub]

great stuff! keep us updated- I am at the stage where I am about to solder- but I need to plan chassis layout-- Thank you for the pdf as well that will be very useful for myself and other newbies in the planning stage-where did you get the coke if u dont mind me asking?

[Ty_Bower]

The choke and the power transformer are both Hammond. I ordered them from Antique Electronic Supply (tubesandmore.com).

I moved things around a little since I posted the .pdf of the chassis layout. I decided I hadn't left enough room on one edge of the Simple SE board to get the leads into the Phoenix blocks. I wish the aluminum plate I have were just a 1/2" bigger in each direction. I feel like it's just a little bit more cramped than I'd like. I've got no good place to put the RCA input jacks as it is right now.

[Ty_Bower]

Did most of the soldering tonight. I still need to install the voltage regulators, and the last few Phoenix blocks. I wish I had bought a five pin block instead of 2 two pin blocks for the inputs. Oh well. I also need to decide on the coupling caps. I've got some nice K40Y that I'd like to use, but they're huge.