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Construction techniques Questions

7/18/2000 10:10 PM
Matthew Springer
Construction techniques Questions
So I have two main questions:  
1) How does everyone build their circuit cards and why do you pick your method?(eyelets, turret lugs, nails)  
2) What order do you typically install things in the chassis in? (sockets and heater wire, xformers, etc.)
7/18/2000 10:13 PM
Matthew Springer
Re: Construction Technique Questions
Boy, that title exhibited terrible grammar! Good thing my mother, the English teacher, doesn't build tube amps!
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7/19/2000 12:41 AM
Re: Construction techniques Questions
"1) How does everyone build their circuit cards and why do you pick your method?(eyelets, turret lugs, nails)"
The final choice is preference/convienence. I've used both eyelets and turrets and prefer eyelets. To me they are just easier to work with. Drilling for turrets without a drill press, unless you have a keen eye its hard to get the turrets to stand perfectly straight.  
I'm going with turrets on my next project that is starting to form. Space is kinda at a premium so I'm thinking it will work out better for me. Normally it's eyelets.  
"2) What order do you typically install things in the chassis in? (sockets and heater wire, xformers, etc.)"
From paper it goes on the chassis from the ground up. Normally punch for the sockets and mount the transformers. Build up the board and lay that in the chassis and look for conflicts with it's placement and where the pots/jacks/sockets will go. If all looks good I then mount the board and again check for problem areas. Then I pretty much strip the chassis and drill all the pot/jack locations.  
When everything is drilled and deburred. I mount all the components again and look for trouble areas. At that point I again pull the board and wire up the power supply, and any of the non board wiring I can. At that stage the board is mounted a couple of hundred times looking for conflicts with unboard runs etc...  
Heaters get hooked up depending on the way I run them. Marshall style tucked into the back of the chassis they get wired up pretty early. Fender style over the sockets--last.  
When everything that can be wired without the circuit board is done. It's mounted for the final time and wired up---and hopefully everything works out as planned.  
I do tests of the power supply along the way to make sure I dont' mess up anything early. Zip tie all wires together that I can get away with and tuck everything neatly away.  
One thing to mention, if your moutning a custom chassis to a custom box I would mount it up first before adding 30pds to your chassis and trying to figure it out.  
best of luck  
7/19/2000 1:24 AM

This is simply my personal method for basic amp construction. Everybody has their own method of doing things.  
1) I use G10 circuit board material and turrets. I Personally prefer the turrets because for me they are easier to change componets when tweaking and for trouble shooting. There is nothing wrong with eyelets, it is a personal preference, what ever works for you.  
I draw my board layout on paper, actual size, (1 to 1) and use a copy as a template to drill the circuit board for turrets and mounting holes.  
2) I usually lay all the pieces out and make sure everthing fits with no conflicts with available "real estate." I decide where the circuit board will go, and drill the mounting holes for the stand-offs, then set the board aside until later.  
Now I punch out the holes for the sockets, transformers, pots, the dog house and board (if applicable) jacks, switches, fuse, pilot lite,etc, then mount all the those mechanical parts.  
Now I start wiring the chassis, starting with the AC cord, switches, fuse, power transformer, and rectifier. If you have filter caps in a dog house it is a good time to wire it up and feed the wires into the chassis, the same goes for the output transformer. I prewire all that I can on the pots and jacks, etc. then wire the heaters.  
I always stuff the circuit board outside the chassis then place it on the stand-offs, and wire the board to the pots, jacks and tube sockets. I usually work from right to left and I like to use another copy of my board layout and mark each step with a hi-liter, and note any changes to the circuit that may occur during construction.  
This is simply my 2 cents worth, I hope others respond to your query, I too would like to see how everyone else does this.  
7/19/2000 1:31 AM

I forgot to ask, what are you going to build?  
and, Good Luck  
7/19/2000 6:57 PM
Matthew Springer

No idea!  
The first thing I'll probably do is revamp my DRRI with a PTP circuit card and better components and sockets, but leave all the xformers alone. One of the sockets is currently so loose that the 6V6's is about to fall out! The plan is to buy another RI and then do them one at a time.  
The next project after that is probably two AC30 clones (run 'em in stereo). I don't really need channel switching or anything, so I'll probably copy Doug Hoffman's layout and go from there.  
The main appeal for me building my own is to get the weight down.  
I've had good luck prototyping some pedals from Aron's site, so that's at least encouraging. Alas, schools these days simply do not teach prototyping skills. I've been hanging out here for long enough that it's time to actually build something. My main dillema at the moment is time and space.  
Being a ASIC engineer in Silicon valley doesn't leave much time and housing prices don't allow much space.
7/19/2000 2:36 PM
Good, solid practice. Of course, looking at your cabinet assembly photos, I wouldn't expect anything else from you.  
I do something similar, except I do the board layout on a PCB CAD program. This lets me move things around for the cleanest placement and simplest wire runs. It's easier for me than the paper copies of parts, but that's just a personal preference, both ways work fine. Whether the traces on the board get done as etched lines or as hand-wires to terminals is a personal choice as well. And I also prefer turrets.  
It's a kind of epiphany when a technical person first realizes that he can draw things out on paper 1 to 1 size and then just use the paper as an expendable cutting and drilling guide. I use spray adhesive from a crafts store, print the 1:1 layout and then spray the back side with adhesive. Then I can just "tape" the paper in place and cut/drill right through it. All the measurements get done on paper or in the computer. I like computer because I can print the results out on my laser printer at 1:1 and can do all the drawing and rearranging very flexibly. I try to make templates of all the parts that will require placement and spacing on the chassis.  
It's a good trick as you note to keep another expendable paper print of the layout/assembly and just use it up during the construction.  
Good practices!!
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