Circuit Kludging, Ninja Level

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Dr. Sketch-n-Etch
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Circuit Kludging, Ninja Level

Post by Dr. Sketch-n-Etch » Sat Mar 28, 2020 5:20 pm

I'm working on this vocoder, and I realized that the sort of notch ripple filters I used for the BP channels were not appropriate for the LP and HP channels, and what I needed there instead were lowpass ripple filters. Upon meditating on my layout, I came to the conclusion that simply kludging the new circuitry into the old layout was going to be an exercise in chaos and frustration. So what I decided to do instead was strip the old circuitry off of the board entirely, and put the new circuitry on a daughterboard and somehow attach it to the original board.

It should be noted that the original board is quite large and has lots of other circuitry on it (the design of some of which I may also have to revisit later), so I didn't want to simply redo the whole board.

So, here's what I came up with. First, the original board, stripped of the offending circuitry:
StrippedBoard.jpeg
Here is the daughterboard with the new circuitry installed, along with some pins for attaching to the old board:
DaughterboardTop.jpeg
DaughterboardBottom.jpeg
You can see the pins sticking out of the bottom of the board. These are the waste from some very long pins from 1x40 pin headers which I used on another build to attach one board to another. The pins were about two inches long, and I ended up with a pile of roughly one-inch waste pieces, which I kept. (I don't like using such long pins, but Lee's was out of the normal kind.) Anyway, these pins are very stiff, so perfect for making strong connections between boards.

All I had to do was to drill some holes in the original board in the corresponding places where these pins are. In most cases, this was right on the trace I wanted to connect to anyway. In a few cases, I had to bend the pins slightly to make them align. This is how the daughterboard plugged into the original board:
InstalledSide.jpeg
Finally, here is the finished product, all soldered together and ready to reinstall in the vocoder case:
InstalledTop.jpeg
InstalledBottom.jpeg
This kludge is clean and strong enough that I wouldn't feel too bad about keeping it in the final product.

That's ninja-level kludging, bitches!
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Re: Circuit Kludging, Ninja Level

Post by guest » Sat Mar 28, 2020 5:23 pm

that is way to clean to deserve the title "kludge". thats just good design! maybe a standoff for good measure?
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Re: Circuit Kludging, Ninja Level

Post by andandand » Sat Mar 28, 2020 7:33 pm

guest wrote:
Sat Mar 28, 2020 5:23 pm
that is way to clean to deserve the title "
lol that’s what I thought too

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Re: Circuit Kludging, Ninja Level

Post by Moog$FooL$ » Sun Mar 29, 2020 12:35 am

i agree with guest.... could u fit any stand offs there for solid support??

d.

ps. did the small bear order make it through?
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Re: Circuit Kludging, Ninja Level

Post by Dr. Sketch-n-Etch » Sun Mar 29, 2020 1:37 am

With 12 of those pins connecting the daughterboard to the original board, that connection is as strong and stiff as it can be. There is no need for any further reinforcement at all.

And no, the Small Bear order has yet to leave Brooklyn. However, my wife appears to have been mistaken about goods from New York being banned in Canada, because I can find absolutely no mention of it on the internet, and I have scoured all of the Canada Customs sites. Hence, I expect the order to arrive in a reasonably timely fashion just as soon as Small Bear decides to send it. Steve Daniels has said that he will be processing all outstanding orders over the next 5 to 7 days (and that was 2 days ago). The Small Bear site is shut down at present, so he won't be receiving any more orders to process.
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Re: Circuit Kludging, Ninja Level

Post by Moog$FooL$ » Sun Mar 29, 2020 9:14 pm

good news all around then. :)
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Re: Circuit Kludging, Ninja Level

Post by Dr. Sketch-n-Etch » Mon Mar 30, 2020 1:31 am

Well, I'm happy to report that I tested the new circuitry tonight, and it worked perfectly. The kludge was a complete success. That takes care of the HP and LP channels of the vocoder.

Tomorrow, I'll (re)test all the BP channels to make sure they are working perfectly, then I'm going to build a "Freeze" circuit which I laid out a couple of days ago which will freeze the vocoder (make it get stuck on a certain vocal formant) when a footswitch is pressed. Luckily, I had Sends and Returns of all the AGC CVs for all 16 BP channels because of a big switching matrix I built to re-route the CV signals to different channels. I didn't have Sends and Returns for the HP and LP channels, but I fixed that with the daughterboard. Also, the way I laid out the switching matrix boards (there are two, and each one handles 8 BP channel CVs), I'll be able to just plug the Freeze board onto the stack with very little change in the existing wiring. I just love it when a plan comes together. Also, the Freeze will be able to be gated from any 5V gate signal, envelope, or LFO, so that oughta be interesting.
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Re: Circuit Kludging, Ninja Level

Post by Moog$FooL$ » Mon Mar 30, 2020 2:16 am

nice development.... how much does this cost to build anyways?? not including build time.

d.
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Re: Circuit Kludging, Ninja Level

Post by Jarno » Mon Mar 30, 2020 3:58 am

That's not a kludge, that's a modular filter unit :)

(if you can't fix it, feature it)

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Re: Circuit Kludging, Ninja Level

Post by Dr. Sketch-n-Etch » Fri Apr 03, 2020 12:01 pm

Yesterday I did another epic kludge...

I designed this board to do a "Freeze" function for my vocoder. It has 18 track-and-hold circuits on it and is 4" x 6". The layout wasn't particularly tight, but the board has to connect to another board by 16 pins on the left edge, and out to some existing external wiring by 16 pins on the right edge.
Freeze.png
There was no way to route the inputs and outputs of the various T&H circuits to those pins using traces, so I wired all the internal pins to the edge strips using crimp pins and MTA-100 connectors. However, another board has to go on top of this board, and to make room for all the wires, the board stack was now too high to fit in the case. (The daughterboard discussed above also added to the height of the stack.)

Hence, I decided to make a second board whose only function is to replace all that wiring. Here is the image of that board:
FreezeKludge.png
This board has pins facing downward, and I replaced all the MTA-100 connectors with pin sockets. The result: it worked perfectly, and now the board stack fits easily under the lid of the case.

(You may see that one 4-pin header and one 3-pin header are not included in the kludge board. This is because these connections do not go to the side strips, but are wired elsewhere in the vocoder circuit. It was not a mistake.)
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Re: Circuit Kludging, Ninja Level

Post by EATyourGUITAR » Fri Apr 03, 2020 4:56 pm

using plated bus wire as standoffs? I love it and hate it at the same time. I like cheap things. I would be worried about how many times I can desolder the second PCB before the pads lift. if you don't need to get in there then it works good I think. I wonder about through hole sometimes. I think it is great for prototypes exactly because it can be fixed without throwing it out. you have all those test points right there. you can see everything easy. they are super good for that.
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Re: Circuit Kludging, Ninja Level

Post by Dr. Sketch-n-Etch » Fri Apr 03, 2020 10:29 pm

EATyourGUITAR wrote:
Fri Apr 03, 2020 4:56 pm
using plated bus wire as standoffs? I love it and hate it at the same time. I like cheap things. I would be worried about how many times I can desolder the second PCB before the pads lift. if you don't need to get in there then it works good I think. I wonder about through hole sometimes. I think it is great for prototypes exactly because it can be fixed without throwing it out. you have all those test points right there. you can see everything easy. they are super good for that.
I don't know about "plated bus wire" -- the pins on that daughterboard are pieces of pin-header pins from one of these:
male-headers-long.jpg
except that the pins were twice as long, so I had a lot of waste. It was the waste pieces that I used. These are square in cross-section and very stiff. That daughterboard isn't going anywhere.

As far as desoldering and lifting traces, I use a Hakko FR-301:
hakko fr-301.jpg
and it makes desoldering very quick and easy, so the traces are not really damaged. You apply the tip to the solder joint for about half a second and squeeze the trigger, and virtually all of the solder is sucked off very quickly. The part basically falls out afterwards, and the trace is as good as new. I haven't tried it, but I'd guess that you could solder and desolder 4 or 5 times before lifting a trace with one of these. It helps if the pads and traces are large.

Of course, I would never advocate building a circuit this way on purpose. I had to change a small (but significant) part of a larger circuit, and decided that this was the easiest and most painless way to do it. However, if I make another vocoder, I'll just make the board properly to start with.
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Re: Circuit Kludging, Ninja Level

Post by Dr. Sketch-n-Etch » Fri Apr 03, 2020 10:50 pm

Moog$FooL$ wrote:
Mon Mar 30, 2020 2:16 am
nice development.... how much does this cost to build anyways?? not including build time.

d.
It's about $400 at this point, I think. There are 86 ICs in this build -- mostly TL074 and TL072, but also quite a few V2164, DG409, and DG444. That's probably about $250 just in ICs. There's a large transformer that was $17. Then there are 220 polyester film caps ($44.00) in about 15 different values, and hundreds of 1% resistors in many different very specific values ($0.042 apiece) and many other 1% resistors in more standard values ($0.017 apiece). Plus the PCB material, all the supplies, the wire, other odds and ends, and a pile of pin connectors (probably about $25 worth). I got the case for free from some university surplus (remember that big haul we made from AMPEL?)

But can you put a price on having this much fun?
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Re: Circuit Kludging, Ninja Level

Post by Flounderguts » Fri Apr 03, 2020 11:53 pm

I like the re-use of the pins. That's my kind of jam. I think I would have used a little heat-shrink on them, though.

I like your mid-board solution as well! pretty sweet idea that I might have to steal for a stalled project.
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Re: Circuit Kludging, Ninja Level

Post by EATyourGUITAR » Sat Apr 04, 2020 8:21 am

thanks for the tips. I learned a lot.
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