[BUILD] Bytes Turing Machine expander

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windspirit
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Post by windspirit » Tue Aug 23, 2016 4:11 pm

Ok so based on what you are saying you just need to adjust the trimmer, which just changes the overall amount of modulation. So:

Set your length knobs fully CCW.

Apply a 10V DC voltage to the CV input (unless you want to be able to sweep the entire range with 5V, then apply a 5V signal)

Turn the CV attenuverter fully CW

Adjust the trimmer until you get close to 9V on the ADC's pin 1.

Let me know if that helps ;).

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atari5200
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Post by atari5200 » Tue Aug 23, 2016 8:49 pm

Would that still be the case if I'm showing the same amount of voltage coming from the trimmer as I am feeding into the CV in?

I'm going to try this after work tomorrow though, it has to be something simple! :party:

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windspirit
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Post by windspirit » Tue Aug 23, 2016 10:59 pm

atari5200 wrote:Would that still be the case if I'm showing the same amount of voltage coming from the trimmer as I am feeding into the CV in?

I'm going to try this after work tomorrow though, it has to be something simple! :party:
Geez I hope so, or else the fix may be more complicated. Its worth a shot either way!

Also someone asked me to show which trace need to be replaced if the bytes expander is removed. If you cut the trace instead of removing R14 (which I still haven't added to the build docs) then here is where you need to add a jumper incase you :waah: remove the Bytes expander. (its the yellow trace.)

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nevetsokyeron
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Post by nevetsokyeron » Wed Aug 24, 2016 5:55 pm

Nice... thanks for posting that board image. That helps a bunch. I wanted to double check my cut trace and make sure I didn't damage the one next to it. :sb:

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atari5200
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Post by atari5200 » Fri Aug 26, 2016 1:14 pm

windspirit wrote:
atari5200 wrote:Would that still be the case if I'm showing the same amount of voltage coming from the trimmer as I am feeding into the CV in?

I'm going to try this after work tomorrow though, it has to be something simple! :party:
Geez I hope so, or else the fix may be more complicated. Its worth a shot either way!
OK, tried this out and it didn't solve my issue.
After doing some more measuring I've narrowed down my problem to somewhere between Pin 7 of the TL074 and Pin 1 of the TL072. Whatever voltage is present on pin 1 of the TL072 seems to be what's present on pin 1 of the ADC0820. I'm not sure if this is accurate, but my measurements line up! So if I feed +5V at my CV input, I can measure that same voltage at pin 7 of the TL074, as well as at the wiper pin of the trimmer (and the trimmer is wide open at this point) However, then I read -2.36 at pin 8 on the TL074, 0V on pins 9 & 10, -11.75V on pin 11, 0 on pins 12 & 13 and -2.36V on pin 14.... then if I measure at pin 1 of the TL072 it's 2.36V, as I guess would be expected given the readings above...and that's the offset that's being fed to pin 1 of the ADC0820.
Visually my resistors appear to check out to be the proper values, but this seems to indicate a problem somewhere in there, maybe with R12, 13, 14, 15? Is there any way to narrow this down short of just desoldering them and putting in new ones? Should I be inspecting other resistors instead? Should I be reading a higher value at the trimmer?
My soldering job is clean but to be on the safe side I reflowed my joints, happy to post a pic but cold joints don't appear to be an issue.

Thanks for your help, I'm sure this is going to turn out to be 1 small bum component somewhere...

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atari5200
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Post by atari5200 » Sat Sep 03, 2016 11:11 am

OK, tried a few things and made some progress but at the same time, not really any!

I reflowed *all* my joints just to be on the safe side, no change.
I visually checked all my resistors, they all look like they are correct.
I replaced the trimmer since after I reflowed my joints I started to get some inconsistent readings. That helped a bit in that now I get the proper gain out of it, if I feed 5V in I can boost it up to 10V with the trimmer all the way open, previously my other trimmer was only giving me 1x1 gain. So that's an improvement, but the voltage division that I was experiencing before is still present.
I swapped out both the TL074 and TL072 just to see if that would help, but there was no change. If I measure pin 7 of the TL074 I get the voltage as set by the trimmer, awesome. However it gets roughly halved somewhere after that. If I set the trimer to feed say, 10V to the TL074, I will measure that voltage at pin 7, so far so good, but then if I measure pins 8 and 14 on the TL074 I get a reading of about -4.8V, and that's what hits my TL072 and then pin 1 of the ADC0820.

I'm at a bit of a loss at this point. The fact that the module works as expected when I use the knobs is a good thing, but this issue is perplexing. Any thoughts based on what I reported above?

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Post by charonme » Sun Jan 07, 2018 4:30 pm

the supply voltage for the ADC0820 in the mystic circuit mouser cart is listed as 5v, but I don't see any 5v regulator in the BOM. Am I missing something?

are there multiple different versions of the ADC0820 out there and only some of them work with this design? or do they all work?
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Post by windspirit » Sun Jan 07, 2018 5:40 pm

Check the Data sheet, it says 10V and there is a 9V regulator in the project. Sometimes mouser messes up entering the data.

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windspirit
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Post by windspirit » Sun Jan 07, 2018 5:44 pm

atari5200 wrote:OK, tried a few things and made some progress but at the same time, not really any!

I reflowed *all* my joints just to be on the safe side, no change.
I visually checked all my resistors, they all look like they are correct.
I replaced the trimmer since after I reflowed my joints I started to get some inconsistent readings. That helped a bit in that now I get the proper gain out of it, if I feed 5V in I can boost it up to 10V with the trimmer all the way open, previously my other trimmer was only giving me 1x1 gain. So that's an improvement, but the voltage division that I was experiencing before is still present.
I swapped out both the TL074 and TL072 just to see if that would help, but there was no change. If I measure pin 7 of the TL074 I get the voltage as set by the trimmer, awesome. However it gets roughly halved somewhere after that. If I set the trimer to feed say, 10V to the TL074, I will measure that voltage at pin 7, so far so good, but then if I measure pins 8 and 14 on the TL074 I get a reading of about -4.8V, and that's what hits my TL072 and then pin 1 of the ADC0820.

I'm at a bit of a loss at this point. The fact that the module works as expected when I use the knobs is a good thing, but this issue is perplexing. Any thoughts based on what I reported above?
Hey Atari, sorry I never responded to this. If you are still following this thread I am still not sure if your issue is that your unit is not working or that you are seeing voltages that you dont expect when you sniff around in the circuit. Did you try calibrating the module in the way that I suggested earlier?

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Re: [BUILD] Bytes Turing Machine expander

Post by gbanfield » Mon Jul 27, 2020 6:21 pm

Hey folks, not sure how many eyes are falling upon this thread these days, but just a quick note:

Buit the BYTES and put it in a Magpie Mod faceplate with voltages, pusles and TM. SO COOL! I ordered everything straight off the github BOM, and noticed that there's a tiny typo--the Bourns trimmer listed has offset legs (I noticed that the straight legged cousin is correctly listed in this thread above). I just bent the legs to fit and everything's fine, but thought I'd throw it out there!

Many thanks to all those who have chimed into this wonderful, weird and ever-evolving project :)

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