fallenturtle

MDF board to mount control suface compontents... bad idea?

11 posts in this topic

My MIDIbox SID project is using a C64/VIC-20 keyboard as its control surface. The encoders and switches were to be mounted to the PCB that attaches to the keyboard frame (with wires directly attached the the component leads instead of using the PCB's own traces) but I've decided that's a bad idea since I'll have to go through extra steps to make sure none of the preexisting traces on the board short anything.

My new plan is to get some board like material similar in density and thickness to the original keyboard PCB, cut it to size, and use it instead. I was thinking of MDF because it seems it can match the requirements of being thin yet sturdy, but I wasn't sure if this was a bad idea, like if there might be moisture in MDF that could cause shorts. So I thought I'd ask you folks who are more seasoned when it comes to materials and electricity.

Would MDF be a bad idea and if so, what would be a good alternative?

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I can't quite picture the concept, could you draw something?

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Point to point wiring on MDF isn't a  bad idea as much as it is heavy and thin MDF tends to be brittle.  The SID CS isn't that large so I don't see flex as a huge problem.  Hardboard is a decent alternative if you're careful.  For either, take measures to avoid tear out.

All that said, when I created my first MB some 15 years ago (man it's been a long time) I had all sorts of trouble with getting a clean fabrication that I was proud to show off, so I've been using Lexan or CNC'd aluminum.  Moisture isn't never an issue and lexan takes vinyl overlays quite well.  I usually paint the back and letter the front for a candy coated look.  The rest of the enclosure can be built out of anything.

Edited by Digineural

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I'm lousy at drawing, but i took some photos to illustrate what I'm doing.

The knobs I got wedge perfectly into the cavities for the keyboard switches on the frame. Those leads will attached to wires between the PCB and the frame and come out a hole somewhere. The switches mount into the board using holes I've drilled. In one of the attached pics you can see the leads sticking through.

My skills using a Drimel drill press have proved less than ideal when it came top lining up the spinning bit with the mark for the hole and so some of the drilled holes have been off by a few mm. I feel bad wasting this keyboard PCB and in hindsight I would have gone straight to creating a board like I'm going to do now (I was less "woke" to retro computer preservation than I am now).

 

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On 9/10/2019 at 4:43 AM, Digineural said:

Point to point wiring on MDF isn't a  bad idea as much as it is heavy and thin MDF tends to be brittle.  The SID CS isn't that large so I don't see flex as a huge problem.  Hardboard is a decent alternative if you're careful.  For either, take measures to avoid tear out.

All that said, when I created my first MB some 15 years ago (man it's been a long time) I had all sorts of trouble with getting a clean fabrication that I was proud to show off, so I've been using Lexan or CNC'd aluminum.  Moisture isn't never an issue and lexan takes vinyl overlays quite well.  I usually paint the back and letter the front for a candy coated look.  The rest of the enclosure can be built out of anything.

I'm actually building this inside of a VIC-20 case. I didn't always plan to be anachronistic, and was going to put this inside a C64C case, but there wasn't enough room for the keyboard and the mb-6582.

If money wasn't a problem, I'd create a custom PCB, but alas.

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How about veroboard/perfboard? Needs fairly standard spacing to work though.

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42 minutes ago, latigid on said:

How about veroboard/perfboard? Needs fairly standard spacing to work though.

I thought about it, but I do think the spacing and size requirements might make that hard. Is there a such thing as a perfboard without the metal bits?

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Sure you can buy protoboard without copper or just drop a normal piece in the etching solution or even file off the metal. It's also no issue to widen some of the holes.

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If it is in your budget you might want to look into an xy slide for your drill press. perfect aligned holes. You can make your layout in inscape then  print it and tape it to a sheet of lexan or plexiglass  to see right where to drill. Aluminum is a lot stiffer but has a bit more cost. You will want to attach your panel to a scrap piece of wood so you are not drilling into your xy slide.

https://www.ebay.com/itm/mini-Bench-Drill-Press-Vise-Fixture-Worktable-X-Y-Cross-Slide-Milling-Machine/163791745756?hash=item2622bfb2dc:g:jGoAAOSwhgtbx-BX

What you are doing will work but you may have some issues with your encoders pushing back through. They make encoders that are threaded that you can put a nut on so this does not happen. I would not recommend gluing them as they will be hard to service.

 

I have been able to also do a pretty good job with printing my layout out with the centers of the holes marked with an x and drilling the first hole with a really tiny bit. The smaller the pilot hole the less error you should have in your finished holes. A self centering step bit is also really helpful for stepping the holes to the size you want.

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On 9/16/2019 at 0:12 PM, gerald.wert said:

If it is in your budget you might want to look into an xy slide for your drill press. perfect aligned holes. You can make your layout in inscape then  print it and tape it to a sheet of lexan or plexiglass  to see right where to drill. Aluminum is a lot stiffer but has a bit more cost. You will want to attach your panel to a scrap piece of wood so you are not drilling into your xy slide.

https://www.ebay.com/itm/mini-Bench-Drill-Press-Vise-Fixture-Worktable-X-Y-Cross-Slide-Milling-Machine/163791745756?hash=item2622bfb2dc:g:jGoAAOSwhgtbx-BX

What you are doing will work but you may have some issues with your encoders pushing back through. They make encoders that are threaded that you can put a nut on so this does not happen. I would not recommend gluing them as they will be hard to service.

 

I have been able to also do a pretty good job with printing my layout out with the centers of the holes marked with an x and drilling the first hole with a really tiny bit. The smaller the pilot hole the less error you should have in your finished holes. A self centering step bit is also really helpful for stepping the holes to the size you want.

I think my accuracy issues might be more related to the drill press itself. There's definitely some play with the arm that moves the drill down and maybe there's a way I can tighten it, I'll have to look, but probably not, its pretty cheap. I assume the slide won't help with that?

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It depends how bad the deflection is you may be able to shim it to get enough of the play out or press it to the one side for every hole. If you are using something like a Dremel 220-01 and you drill the first hole with a small 1mm or even .5mm bit you should not have so much wander. You mention mm off above. If you start drilling with a 6mm bit the holes will be all over the place as the crosspoint is likely a mm or two and that will move your work quite a bit and make it very hard to drill a good hole where you want it. You should be able to do that even without the slide if you print and mark your centers on a printed template. They should come out just about perfect with the slide. Test it out on a scrap piece of something and see how it does.

 

Here is a sample picture of the center of the drill holes marked you can use a dot or an X  what ever is easier for you.

x0xb0x_mainpanel_sample.png

Edited by gerald.wert
edit

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