Dunnington 281D build thread

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tarandfeathers
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Dunnington 281D build thread

Post by tarandfeathers » Fri May 29, 2020 6:05 am

I announced these in the Buchla subforum but I thought it would be worth having a thread for folks to discuss building these modules.

First off, full docs are at https://github.com/DunningtonAudio/281D

As per the notes, for hand assembly it's best to solder the lowest profile/finest pitch parts first, and work up to the highest profile parts.

Looking forward to seeing how people get on with these, any feedback on buildability etc. is definitely welcome.
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search64
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Re: Dunnington 281D build thread

Post by search64 » Fri May 29, 2020 7:18 am

That looks really great! Any plans for more modules? Perhaps even a 218?

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Re: Dunnington 281D build thread

Post by tarandfeathers » Fri May 29, 2020 2:47 pm

search64 wrote:
Fri May 29, 2020 7:18 am
That looks really great! Any plans for more modules? Perhaps even a 218?
Some vague ideas but nothing very concrete right now. I was chipping away at these for about a year on and off, and the things I personally need most as of now would probably be new designs, so I wouldn't hold your breath, but I'm sure I will keep at it in some form...
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Re: Dunnington 281D build thread

Post by finlayshakespeare » Thu Jun 25, 2020 3:20 pm

Finally got the pots for a couple of these today and put one of the two boards together. I ordered some boards w/ a stencil so I could do a pick + place job, then stick the boards in our reflow oven. Channel C seems to be fully working, but all other channels seem to be stuck super slow. Going to investigate what's going on tomorrow and will report back - I'm certain it's bad joints or shorts.

One bit of feedback I would give - the footprint for the SOD-323 parts is quite tricky to deal with, even with stencil + paste + reflow. Even reworking them with the iron, I'm still not particularly confident with how those joints have come out. Otherwise, absolutely top job and looking forward to getting the whole module working!

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Re: Dunnington 281D build thread

Post by finlayshakespeare » Fri Jun 26, 2020 6:29 am

finlayshakespeare wrote:
Thu Jun 25, 2020 3:20 pm
Finally got the pots for a couple of these today and put one of the two boards together. I ordered some boards w/ a stencil so I could do a pick + place job, then stick the boards in our reflow oven. Channel C seems to be fully working, but all other channels seem to be stuck super slow. Going to investigate what's going on tomorrow and will report back - I'm certain it's bad joints or shorts.
Turned out to be the 3906 pairs! I has assumed they were symmetrical, but they aren't - teaches me for next time! I'm now basking in quad AD goodness :party:

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Re: Dunnington 281D build thread

Post by tarandfeathers » Fri Jun 26, 2020 6:37 am

finlayshakespeare wrote:
Fri Jun 26, 2020 6:29 am
Turned out to be the 3906 pairs! I has assumed they were symmetrical, but they aren't - teaches me for next time! I'm now basking in quad AD goodness :party:
Excellent! And a good catch - the pin 1 marker on those isn't super easy to see. I'll update the notes PDF to highlight this.
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Re: Dunnington 281D build thread

Post by finlayshakespeare » Fri Jun 26, 2020 6:57 am

tarandfeathers wrote:
Fri Jun 26, 2020 6:37 am
finlayshakespeare wrote:
Fri Jun 26, 2020 6:29 am
Turned out to be the 3906 pairs! I has assumed they were symmetrical, but they aren't - teaches me for next time! I'm now basking in quad AD goodness :party:
Excellent! And a good catch - the pin 1 marker on those isn't super easy to see. I'll update the notes PDF to highlight this.
Sure thing! It mainly came from us working with symmetrically paired 3904s... I forget the exact part number, but it's the same footprint, and I had simply made the assumption they were all like that. Of course not :lol:

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Re: Dunnington 281D build thread

Post by jimfowler » Sun Jun 28, 2020 7:33 pm

Worth noting: the pcb silkscreen demarcates polarity for those parts but yeah a note in the BOM or build notes/guide would be helpful.

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Re: Dunnington 281D build thread

Post by tarandfeathers » Mon Jun 29, 2020 8:01 am

I've added a note in both the notes and against the line for the transistor pairs in the BOM files.
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Re: Dunnington 281D build thread

Post by CliffordMilk » Mon Jul 20, 2020 6:50 am

Just to be sure, on a faithful Buchla setup, should I omit the **99 components highlighted in the build doc as needed for a standard gate? Also, could someone perhaps upload a high-res image of a completed board? I find this can usually answer most questions for me.

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Re: Dunnington 281D build thread

Post by tarandfeathers » Mon Jul 20, 2020 8:35 am

CliffordMilk wrote:
Mon Jul 20, 2020 6:50 am
Just to be sure, on a faithful Buchla setup, should I omit the **99 components highlighted in the build doc as needed for a standard gate? Also, could someone perhaps upload a high-res image of a completed board? I find this can usually answer most questions for me.
Yes, you can leave off the *99 components - if you have a look at the schematic PDF it should be clear but I'll see about tweaking the wording in the build notes to make it obvious.

Will see what I can do about a hi-res board photo.
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Re: Dunnington 281D build thread

Post by CliffordMilk » Mon Jul 20, 2020 11:52 am

Cheers. Components just arrived :)

Edit: I see it on the schematic and it is indeed very clear. Thank you.

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Re: Dunnington 281D build thread

Post by CliffordMilk » Wed Sep 16, 2020 12:09 pm

Just finished building the PCB and realised I don’t know how to hook up the power connector. Could someone please tell me or show me an image showing me which pins on the connector I hook up the +15, -15, +12 and Q to?

Apologies for the basic question but this is my first Buchla format build.

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Re: Dunnington 281D build thread

Post by tarandfeathers » Wed Sep 16, 2020 12:26 pm

At the PCB end each wire pad is marked. At the EDAC end the pin numbers are specified in the BOM (in the notes for the power cable wires). For reference though:

Pin 1: Q
Pin 2: -15V
Pin 3: +15V
Pin 4: +12V

A polarising key should be fitted in pin 7 to prevent the possibility of reverse connection. The other pins are all unused on this module.
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Re: Dunnington 281D build thread

Post by jheronymo » Wed Nov 04, 2020 12:51 am

Is anyone able to explain the polarity markings for the semiconductors?

I see that on the SOIC and SOT packages, the silk screen marking line on one end extends a bit farther to cover one corner pin. Would this be Pin 1?

I also see that on the diodes, one end has a solid line and the other end is blank.

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Re: Dunnington 281D build thread

Post by tarandfeathers » Wed Nov 04, 2020 4:46 am

You are correct, the extended line on the SOIC and SOT packages are pin 1. The end with the line on the diodes is the cathode. These markings are per IPC-7351C, which is the current preferred standard for footprints. The good thing about it is that the pin 1 indicator doesn't take up any space outside the component courtyard, which allows denser layouts, and it is still visible after the component is placed which makes inspection easier.
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Re: Dunnington 281D build thread

Post by jheronymo » Wed Nov 04, 2020 9:59 am

Thanks! Agreed, this is a great standard :tu:

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Re: Dunnington 281D build thread

Post by CliffordMilk » Wed Nov 11, 2020 11:23 am

All done and all good :) I’m not very experienced with hand soldering SMD parts but with the excellent supporting docs it was fine. 258D next.

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Re: Dunnington 281D build thread

Post by tarandfeathers » Fri Nov 13, 2020 4:26 am

Excellent, thanks! This is great to hear. It can be a bit of a struggle judging exactly how challenging these things might be for an unknown end user so I'm really glad people are having success with these projects.
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