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First build troubleshooting - Turing machine voltages
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author First build troubleshooting - Turing machine voltages
Micro Stuart
So I've just finished my first build - the Turing machine!
It was really well documented, not too difficult, and pretty fun!

Nonetheless, I've run into my first issue:
my VOLTAGES faders (2,4,6,8) are working. Faders (1,3,57) are not working.
I've tried resoldering those faders once already with no success. I wonder if anyone has any suggestion where the problem might be????

worst case scenario, it's still pretty awesome with 4 steps.. but 8 would be even better. thanks for the help everyone!!
One of the voltages bit signals is not getting from the main board to the expansion board. My guess its the 1 (lsb). Assuming you have the pulses expander and it is not affected, the problem has to be on the backpack or voltages expander.
Micro Stuart
Thanks fuzzbass. Do you think it's just a bad solder?
And I'm sorry, but what do you mean 1 (lsb)?
LSB means least significant bit, but I'm just guessing here...

Are the fader leds just not lit, or is it something else? The Turing Machine and its expanders are kind of unusual...

Try this:
Set the TM big knob fully clockwise
Fill the registers by holding the write switch up
Set the Voltages scale to 10 oclock
Move all voltages sliders to center.

Do you get a consistent CV out of Voltages, or is it fluctuating?
Micro Stuart
Thanks again for clearing that up fuzzbass,
So what you're saying is that it's probably something minor. I've just got to find it !!

From what I can tell, the Turing machine and Pulses are both working fine.
I tried out the test you suggested, and still, only faders 2,4,6,8 are working. When patch out of the voltages module I'm basically only getting 4 pitches/stages when sent to to an oscillator 1V/Oct input.

I guess I'll check out the backpack expander tomorrow and try resodering bad looking joints.

Any other suggestions as to what the problem could be?
I spent a little time this morning trying to reproduce your problem. I thought maybe this would happen if one of the CD4050s on the backpack was bad. A failure of one of these would affect [1234] or [5678], not [1357] so nope...

Another thing to investigate...

The Thonk build docs don't mention this, but some of the solder joints on the PCB conflict with placement of the sliders, and this can cause shorts. These solder joints must be absolutely flat/flush trimmed so avoid this. If there is a bead of solder at these points, it might explain the issue you are seeing. The solder joints involve the TL074 and 10K resistor network. You should be able to inspect without desoldering the sliders. My recollection is that the bottom of the slider is non-conductive, but the sides are not.
I seem to remember I had a similar thing with my first Turing build.
The problem was simply that I'd not seated the Backpack - Voltages power cable properly, so only one row of pins was connected...
Also in this same zone of conflict is R1. If that was shorted, I think the Voltages clock out will be inop.

Failing my previous suggestions, you will need to troubleshoot this as a logic problem. Set the TM big knob to clockwise (so the sequence does not change). Set the sequence length to 8. Start the sequencer and hold the write switch up to fill the registers with ones. All LEDs on the TM array should be lit and stay lit.

Starting from the middle (bit inputs on the backpack CD4050s) look for any that are low. If you have a logic probe, it will be very easy. If you don't, use a scope or DMM. If you are using a DMM, you will need to have the clock speed low enough so your DMM can track the voltage change. Watch each bit position through an entire 8 clock cycle. All of the bits should be high through the entire cycle. If they are all high, trace in the direction of the Voltages expander. If you find one or more bits low, trace in the direction of the TM.

If you look at the schematic, you will notice that some bits are not used in the pulses expander [3568]. So your problem could be stuck bit(s) anywhere along the path from TM > Backpack > Voltages and Pulses might still be fine.
woodster wrote:
I seem to remember I had a similar thing with my first Turing build.
The problem was simply that I'd not seated the Backpack - Voltages power cable properly, so only one row of pins was connected...

That would perfectly explain it seeing as gates [1357] are in a row on that header.
Also, I seem to recall I had to use a little more solder on the voltages connections than I would usually do.
Micro Stuart
I resoldered the voltages/gates connection on the backpack expansion board and now it's in perfect working order. Can't thank you guys enough, especially fuzzbass for offering so many suggestions. I wouldn't have been able to start this DIY a building if it weren't for all the supportive members here on muffs. Hopefully I'll be able to repay this kindness someday in the future as I get better at doing this.

Next onto the Mikrophonie, and then the PEG.
Guinness ftw!
edit: I'm here if you have PEG issues too. Its a great module.
Micro Stuart
You're amazing! Thank you fuzzbass
Hopefully I won't need help, but it's great to know you're here if/when I do!
Cheers Guinness ftw!
I am having this same exact problem and I'm so grateful I have a good lead on how to fix it! Thank you all!
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