DIY Mutable Unsuccessful Builds

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hndmrsh
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Re: DIY Mutable Unsuccessful Builds

Post by hndmrsh » Tue Aug 11, 2020 8:28 pm

extralifedisco wrote:
Tue Jul 07, 2020 6:39 pm
At this point, if you're confident you've ruled out everything else, I'd go ahead and replace the chip. Even if it doesn't fix it, the component price is worth saving yourself an hour of frustration poking at a half-working board.
So! I finally got around to replacing the MCU (had to wait until I did my next Mouser order). Made a total mess of removing the old one - I lifted a few pads off, but very luckily none of them are used in this circuit! But I got the new MCU soldered on and flashed, and...

It works! :party:

Drawing ~117mA on the +12V rail (which is a margin-of-error off from the 110mA listed in the manual), and it runs off my uZeus now too. So excited to have finally got it working, 6 months removed from when I thought I had finished the build! :lol:

Thanks so much for your help and advice!

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Re: DIY Mutable Unsuccessful Builds

Post by aragorn23 » Tue Aug 11, 2020 11:43 pm

cnicht wrote:
Tue Aug 11, 2020 3:02 pm
How are you measuring continuity, with the continuity setting on a DMM?

If you're measuring resistance the pots share a common supply voltage and 0V
Yup, with continuity on a DMM.

I'm not 100% sure what you mean about the common supply voltage and 0v?

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Re: DIY Mutable Unsuccessful Builds

Post by cnicht » Wed Aug 12, 2020 1:35 am

Each pot is connected to 3.3V and 0V

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Re: DIY Mutable Unsuccessful Builds

Post by cnicht » Wed Aug 12, 2020 2:14 am

If you turn pots so their wipers are at 0V then they will show continuity with each other.

The same is true if you turn them to 3.3V.

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Re: DIY Mutable Unsuccessful Builds

Post by aragorn23 » Wed Aug 12, 2020 8:09 am

cnicht wrote:
Wed Aug 12, 2020 2:14 am
If you turn pots so their wipers are at 0V then they will show continuity with each other.

The same is true if you turn them to 3.3V.
Ah right, of course.

I'm beginning to think the problem must be the 4051's. I mean, to have exactly the same issues on two builds on two different boards makes no sense otherwise. I've checked all the other components and there's nothing erroneous. Perhaps I got a bad batch or something?

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Re: DIY Mutable Unsuccessful Builds

Post by cnicht » Wed Aug 12, 2020 8:51 am

Does the multiplexer have the correct signals on its control inputs?

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Re: DIY Mutable Unsuccessful Builds

Post by aragorn23 » Wed Aug 12, 2020 9:31 am

cnicht wrote:
Wed Aug 12, 2020 8:51 am
Does the multiplexer have the correct signals on its control inputs?
That would be pins 1-5 and 12-15, right?

EDIT: I swapped out the 4051 with one from a new batch and the issue remains, so I've definitely ruled out the multiplexer. Could the STM be causing this type of issue?
Last edited by aragorn23 on Wed Aug 12, 2020 10:35 am, edited 1 time in total.

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cnicht
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Re: DIY Mutable Unsuccessful Builds

Post by cnicht » Wed Aug 12, 2020 10:03 am

Pins 9, 10 and 11

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Re: DIY Mutable Unsuccessful Builds

Post by aragorn23 » Wed Aug 12, 2020 10:53 am

cnicht wrote:
Wed Aug 12, 2020 10:03 am
Pins 9, 10 and 11
I've overworked the STM and lifted some pads, so all is lost :doh: Thanks for all your help! I guess that's me starting over again on a fresh pcb...

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Re: DIY Mutable Unsuccessful Builds

Post by cnicht » Wed Aug 12, 2020 11:22 am

I wish you better luck with the next iteration

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Re: DIY Mutable Unsuccessful Builds

Post by aragorn23 » Wed Aug 12, 2020 11:55 am

cnicht wrote:
Wed Aug 12, 2020 11:22 am
I wish you better luck with the next iteration
Thanks. I'm going to triple-check everything before starting!

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Re: DIY Mutable Unsuccessful Builds

Post by snowtires » Thu Aug 20, 2020 2:43 am

I built a Clouds and there is a short that I absolutely cannot find. I'm getting really weird continuity readings, like all the 47uF caps have continuity across them, and IC2's LM1117 has continuity on all pins. I removed some components from the board to see if something was accidentally stuck underneath them, but man I am stumped. If anyone can check these pictures and see if they see something I don't, I would really appreciate it.
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Re: DIY Mutable Unsuccessful Builds

Post by cnicht » Thu Aug 20, 2020 11:28 am

You haven’t said what problem the short is causing

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Re: DIY Mutable Unsuccessful Builds

Post by snowtires » Thu Aug 20, 2020 12:21 pm

The short is causing the 4.7 ohm resistor on input to burn out. I am taking pieces off and a lot of the pads still have continuity where they shouldn't, especially power filtering caps for the STM, shift register and the audio codec. The op amp filter caps are not giving the same continuity issue.

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Re: DIY Mutable Unsuccessful Builds

Post by cnicht » Thu Aug 20, 2020 12:26 pm

Did you test the power rail components before placing the rest of the circuitry?

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Re: DIY Mutable Unsuccessful Builds

Post by snowtires » Thu Aug 20, 2020 1:08 pm

Of course not, I am an idiot. Something is shorting the output of IC2 to ground, that's as much as I can tell.

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Re: DIY Mutable Unsuccessful Builds

Post by forestcaver » Thu Aug 20, 2020 1:49 pm

My suggestions (what I’d do, but take with a pinch of salt):
Open eagle board file. Type ‘sh +3v3’
That’ll show you the +3v3 line. Something is shorting from it to GND
Look at the board under high magnification around those areas (looks like you have lots of solder blobs and loads of flux on there plus many questionable joints and likely bridges but the images aren’t good enough quality to be certain). Most likely places imo are the stm32, mini-jtag or dac. If you cant see anything, just take off the dac and stm32 one at a time and see if it resolves it (or blindly reflow the stm32 and dac but that’s not usually an optimal approach)

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Re: DIY Mutable Unsuccessful Builds

Post by snowtires » Thu Aug 20, 2020 2:13 pm

forestcaver wrote:
Thu Aug 20, 2020 1:49 pm
My suggestions (what I’d do, but take with a pinch of salt):
Open eagle board file. Type ‘sh +3v3’
That’ll show you the +3v3 line. Something is shorting from it to GND
Look at the board under high magnification around those areas (looks like you have lots of solder blobs and loads of flux on there plus many questionable joints and likely bridges but the images aren’t good enough quality to be certain). Most likely places imo are the stm32, mini-jtag or dac. If you cant see anything, just take off the dac and stm32 one at a time and see if it resolves it (or blindly reflow the stm32 and dac but that’s not usually an optimal approach)
Yeah, that's what I did and there's still a short. I took off the DAC, the STM and the jtag header and there is still a short. I even used my fancy new desoldering tool to make sure to get everything I could off of the board. There are two spots on the board where the solder mask has come up, I was assuming that this was fine (although not optimal) because both spots go to ground anyway, but maybe the top layer isn't ground? I dunno.

Here's something, how hot are you folks keeping your soldering irons? I've had my at @ 636F/335C for as long as I can remember, but I was checking out a build guide from Dreadbox the other day that say never go above 285C. Is that true? I tried that temp and can barely get the solder to flow. I'm just getting super frustrated because I've been building synths for years and only recently made the switch to SMT, and have had more failed projects in three months than in the past 10 years with through hole. I tried switching to a hot air gun and solder paste and I feel like I was just burning everything, trying to get the resistors to stop moving around when the paste melted, so I went back to a soldering iron.

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Re: DIY Mutable Unsuccessful Builds

Post by Flounderguts » Thu Aug 20, 2020 2:29 pm

I run my through hole at 355C (indicated, I have no idea if that's accurate) I have a thermal imaging camera, and I recorded some video of me soldering with it...the actual temperature of the solder was around 290 to 310 at the end of each joint. I have no idea what the tip temperature was.

When I'm doing smt, I usually run a bit hotter...I like stuff to melt FAST...that way you introduce less heat to those tiny parts. It's sort of like making battery packs...If you try to solder them, you overheat the batteries. But using a capacitive discharge welder (with an arc at around 6000 C!) introduces far less heat into the component.

I find hot air is useful for rework, but less for actually building an smt pcb. Like you, I tend to cook parts with it. A reflow oven or a hotplate with a pan of sand works way better. Or an iron, but it's difficult to solder pads that are UNDER a component. Sometimes suspending the pcb and using hot air on the underside of the board works, but it's a pain to set up. Good solder paste goes a long way, as well.

You might have to remove all the components from the rail and test the traces :cry:
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Re: DIY Mutable Unsuccessful Builds

Post by snowtires » Thu Aug 20, 2020 2:43 pm

Flounderguts wrote:
Thu Aug 20, 2020 2:29 pm
You might have to remove all the components from the rail and test the traces :cry:
That's where I'm at, I removed every single component from the rail and there is still a short. Testing traces, my favorite. Phewww boy. At least I'm not crazy with that soldering temp, I am not sure what the Dreadbox guy was on about.

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Re: DIY Mutable Unsuccessful Builds

Post by snowtires » Thu Aug 20, 2020 2:51 pm

Wait, the short is gone! Wtf. Ok, time to put parts back on

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Re: DIY Mutable Unsuccessful Builds

Post by snowtires » Thu Aug 20, 2020 4:53 pm

Aaaand now there's a short to VCC. ARGHHHHHHHHHH

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Re: DIY Mutable Unsuccessful Builds

Post by Flounderguts » Thu Aug 20, 2020 5:42 pm

Ah, frustrating...but you're zeroing in on the problem. Did you test your individual components while they were out? It's tough without a set of test tweezers, but I've had luck putting an alligator clip on a set of metal tweezers, picking up the component by one conductor, and pushing the other conductor to the other test pin. It's a real challenge on an 0603 or 0402 LED!
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Re: DIY Mutable Unsuccessful Builds

Post by emmaker » Thu Aug 20, 2020 6:21 pm

snowtires wrote:
Thu Aug 20, 2020 4:53 pm
Aaaand now there's a short to VCC. ARGHHHHHHHHHH
Proper way of doing this is put a part or two on then check for the short, don't put them all on and then measure.

Do not know if this will work and you'll need a DVM that can go down to at least 1/100s of an ohm. Ground one ohm meter lead and then measure all the connections that could be shorted. You'll get readings with very slight differences. Then check the connections with the lowest resistance. We use to use this technique when looking for shorts on computer backplanes.

Jay S.

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Re: DIY Mutable Unsuccessful Builds

Post by snowtires » Thu Aug 20, 2020 7:08 pm

Oh, I tested continuity after every part went on, but continuity for the short I was trying to fix, not the new one I created hah

I will check with my DMM like you said to, hopefully I can figure it out. Man, what a mess!

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