question about Mutron boards.....

[fluxus]

how they made boards? looks handmade or pressed....but how?

[Bernardduur]

I've also seen that on EHX boards.......

What pedal is it?

[fluxus]

it's a phasor II made by mutron of course. the circuit looks very cool and I'd wanna know how they made them.....

[Sir H C]

That was how they made the boards in the 70s.  Often they would then finish by putting a coat of solder on the PCB.

Hand drawn definitely but machine made.

[fluxus]

thanks for repling! honestly, I thought to receive many replies and details about an old and so cool technique to make circuits......someone know if I could find a good empty board to try to draw up a circuit? I mean a material that makes easy the coagulation ...... advices.........thanks you

[R.G.]

In the old days... 

Boards were made by a photo negative process. Here's how it worked.
1. You put a mylar or glass grid on your lighted-from-below drafting table. The grid was usually 0.100" per grid line.
2. You placed a sheet of mylar drafting film on top of the grid. Lighted from below. you could still see the grid. Then you drew the board outline, mechanical features, etc.
3. Place a second sheet of drafting film on top. Draw all of the components in place and connect them with red lines/blue lines for top/bottom traces, respectively. Do all of the layout here.
4. Add a third sheet of drafting film. Onl this one, start putting in the board outline and pads in the places on the grid where the components go. This sheet becomes the pad master.
5. Remove the mechanical drawing so you can still get some light through. Tape in black masking tape where the bottom side traces go.
6. Remove the bottom side sheet and put on a top side sheet if you have top side traces. Tape in the top side traces.
7. Take all of your sheets, flat, not rolled up to preserve the tap in place, to a photolithography store where they do the darkroom stuff to convert your taping to photo negatives, correcting the size at this time if you did the drafting at 2:1 size or 4:1 size.
8. When negatives were done, take the negatives to a photo PCB maker who used a photo process to make the boards from negatives.

The reason the traces all flow around is that the PCB tape was prone to peeling up if you did too sharp a curve or stacked too many pieces in a sharp corner.

The boards were never "printed" by adding gook onto an insulating board. They were always photomasked onto copper clad and etched. Simple boards with crude enough patterns could be screen printed with resist ink, followed by a chemical etch.

[orgaqualia]

I would have never had the patience. Plus I can't draw a line with a ruler...

[R.G.]

I would have never had the patience.

Not many people ever did. Doing PCB layout was a highly skilled, disciplined specialty. That's one reason so much effort has been put into getting computers to do the heavy lifting. We could never have the sheer abundance of electronic widgets we have today if they all had to be laid out by hand.

By the way, I know of one instance where a board with sixteen layers of copper traces in the board was laid out by that method. That takes more than patience. 3D chess is trivial compared to the mental gymnastics needed to do that.

[fluxus]

I have to translate well cause I'm italian but Thanks alot for your reply!

[Torchy]

Often they would then finish by putting a coat of solder on the PCB.

Not quite, the components were fitted and the leads trimmed by hand. The protruding leads were bent over to hold the components in place and the pcb was then floated across a solder bath to solder the leads. This resulted in a coating of solder on the traces as solder masks werent used then. Its the flow-soldering that gives the boards a home-spun look.