Build Questions: Layout

[benoit]

I now have a blank chassis and transformers (the Twin set from mojo), and am feeling a little stuck. I've never done a layout before, and none of the layouts I've seen are quite what I'm going for (100W ODS HRM based on the ODS-101 HRM schematic, no loop, no 'verb). I don't know exactly where to begin. I know roughly from pictures where everything should go but I don't want to screw anything up.

1. What size are the boards in the real thing (Preamp, rectifier, relay, HRM, power, am i missing anything)? I've done a lot of searching and the only sizes I've found are for d-lite boards.

2. Is there an existing layout (using a laydown PT, HRM, no loop or 'verb) that I haven't discovered yet? If so I could print to scale and go off that. Otherwise how do I go about placing components? Just order everything, see where it'll fit? Something more complex?

3. Is there any rule for the tube spacing/placement?

4. Is there a standard eyelet spacing?

I'm sure there's more but that's all I've got right now.

[odourboy]

PM sent.

[briane]

normster has some great layout drawings on his site. The can be easily adapted to whatever you want. I just draw it out on paper myself with my changes, ala new layout.

good to have a sheet of garolite, so you can adjust the size of the board to what you want.

I lay out the boards by eye, keeping a bit of space between components. Eyelets/turrets on 3/8" work well, if components are small it can go down to 1/4". my HRM with dumbleator build came out really tight on space, but it still sounds great.

Take you time laying out the g10, once drilled its set in stone.

You hear a lot about tube spacing, but I have pushed the limits on some builds....down to about 1 1/8" if the tubes fit. What I have noticed is there is a difference in tone related to where the power tubes sit related to pre-amp tubes. I often need 2 rows of tubes, to fit the power tubes, and in that case I space them between the pre's (PI and v2), and down the line away from the pre's.

[Bob-I]

If you don't have a drawing program, like Visio, get some drawing paper in 1/4" grid. Draw out the layout with a ruler. 3/8" spacing between eyelets is good. Tubes need room for cooling so keep the power tubes about 1 1/2" to 2" apart, preamp tubes 1 1/2" apart. Line up the eyelets as close to the tubes as you can.

Use Normster's drawings as a start, add what you need to them on the drawing paper.

Good luck.

[benoit]

Thanks, I think the main thing is to quit worrying about it and draw it up, then scan it, have it checked for gaping errors, and build the @#%^ thing.

[Normster]

You don't mention what the chassis dimensions are, but assuming a 19" x 8" x 2.5", you can space tubes at 2.5" (with the first preamp tube 1.5" from the edge of the chassis). I generally line the tube centers up 1.75" from the back of the chassis.

Control knobs are spaced at 1.375" on the front panel. You can go tighter but keep in mind that chicken head knobs are 1.25".

Best thing is to blow up some chassis shots of Dumbles and break out the tape measure. I use Visio to scale the photos, but it can still be done the old fashioned way.

[benoit]

Thanks Norm (and everyone else). My chassis is basically standard size. I'm not stuck anymore.

[benoit]

How important is transformer placement? I assume I'd want to give the power tubes at least an inch or so and maybe about an inch and a half from the side? The PT is supposed to have its long side parallel to the front/back, right? OT and choke have their bells pointing toward either side? Any other advice for Transformer mounting?


How about the panels? How much space do the mini switches need? The input jacks?

I'm starting to thing I should probably design my faceplates sooner rather than later.

[Bob-I]

How important is transformer placement? I assume I'd want to give the power tubes at least an inch or so and maybe about an inch and a half from the side? The PT is supposed to have its long side parallel to the front/back, right? OT and choke have their bells pointing toward either side? Any other advice for Transformer mounting?

Make sure that the windings are not parallel. One xformer facing front/back, one xformer facing right/left. I've found that the choke at a 45 degree is quietist if both xformers are mounted on top of the chassis.

Dumble puts the PT through the chassis like Fender so the choke can be at 90 degrees to the PT, then the OT 90degrees to the choke. Nothing on the same plane to allow interaction.

How about the panels? How much space do the mini switches need? The input jacks?

I like an inch for the mini toggles and input jack.

I'm starting to thing I should probably design my faceplates sooner rather than later.

Yes, do the front panel all at the same time so no mistakes are made.

[benoit]

what works best as far as choke and OT orientation?

For the choke, should the leads come out on the PT side (makes more sense to me this way) or the OT side (and if so can you put them through the same hole in the chassis)? Bob-I suggested turning the choke diagonally. Has anyone else found this useful or can I get away with everything straight?

For the PT, should the primaries be closer to the PT or further away? Either way seems to make fairly good logistical sense but beyond that I'm not sure what the limitations are.

As for boards, if you're going double, can you use the 1/16" g10 for everything or should you use 1/8" for the boards and 1/16" for the backing?

[Bob-I]

For the choke, should the leads come out on the PT side (makes more sense to me this way) or the OT side (and if so can you put them through the same hole in the chassis)?

That fine. The noise issue with xformers is more in the magnetic than electrical.
'

Bob-I suggested turning the choke diagonally. Has anyone else found this useful or can I get away with everything straight?

Remember I said if the xfomers are top mounted, not through the chassis. Through the chassis allows you to put the windings on 3 planes.

For the PT, should the primaries be closer to the PT or further away? Either way seems to make fairly good logistical sense but beyond that I'm not sure what the limitations are.

Doesn't really matter, its dressing them out inside that matters more.

As for boards, if you're going double, can you use the 1/16" g10 for everything or should you use 1/8" for the boards and 1/16" for the backing?

I built one amp with 1/6". The board feels really fragile. I'd stick to 1/8" for the board, 1/16" is fine for the backing.