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 Forum index » DIY Hardware and Software » Thomas Henry designs
Troubleshooting my UD-1
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creatorlars



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PostPosted: Mon Jan 14, 2008 1:33 am    Post subject: Troubleshooting my UD-1
Subject description: Help me please! :)
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Okay, so I finally finished my modular case and power supply this week and have been spending the weekend trying to get my UD-1 working. It seems like everything is working, but it is operating at several octaves higher than it should be, and with a constant tone in the background at all times.

I've triple checked all the wiring to the pots/jacks with my multimeter and everything checks out perfect according to the tech guide. And I swapped out fresh ICs (performance is exactly the same.) All ICs are getting power to the correct pins. Status LED flashes correctly (I am using a piezo drumpad to the trigger in jack, which seems to trigger the unit just fine.)

Sounds like this may be an issue with a component value somewhere? some of the caps i used were bought at the local electronics store and may be old, but I have no way to test them. Is there anything I should check first as a potential culprit for this kind of issue?

I've attached a sound sample of what I'm talking about. My power supply is sending +14.85 & -15.05 but I'd been told that not having it exact wouldn't make a difference (like this anyway.)

Thank you in advance for any help.


badud1.mp3
 Description:
Sound sample of my buggy UD-1. Seems to be operating at a much higher pitch range than it should be, and there is a constant squeal in the background. During this sample I adjust the "Initial" knob, the "Waveform Blend" knob and the

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creatorlars



Joined: Nov 26, 2007
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PostPosted: Mon Jan 14, 2008 2:46 am    Post subject: Reply with quote  Mark this post and the followings unread

I just spent a couple hours going through and triple-checking all the resistor, pot, and capacitor values, as well as resoldering any iffy joints on the top and bottom of the board -- but the problem persists. How frustrating. Maybe there is a bad capacitor? I tested the resistance values with a multimeter. I guess the next step is to study the schematics -- please let me know if any of you have additional ideas on what could be causing my problem.

Thanks,
Lars
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bugbrand



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PostPosted: Mon Jan 14, 2008 10:59 am    Post subject: Reply with quote  Mark this post and the followings unread

Hmm, sounds like the envelope is working (you can get the bweeeee synth drum sounds) but maybe the VCA isn't working - sounds like it is fixed open. Had a quick look at the schem ---- maybe you've used a 2n3904 instead of a 2n3906?? That's a guess... 3904 is NPN (as used for Q1 and Q2) whereas Q3 needs to be a 3906..

Could be a 3080 problem otherwise maybe??? That's the area I'd be looking anyway...

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creatorlars



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PostPosted: Mon Jan 14, 2008 11:14 am    Post subject: Reply with quote  Mark this post and the followings unread

That's a good tip... thanks! I did double check all my transistors and everything's where it should be, but maybe there's a bad one... I'll try that first thing, checking all the pins from the 3080 and replacing potentially bad parts.

I've tried the LM3080 sent with the board kit, and a CA3080 from Small Bear (as well as an LM566 and NE566) and results are identical.

Is the pitch range supposed to be that high? I understand the VCA affecting the constant tone problem, but why would the VCA be affecting the pitch like that? During the sound clip I rotate "initial pitch" from 0 to 100%, and I'm making sure the CV range and sweep knobs area all the way down...

Assuming I can get this working without shooting myself first, it will at least be a good learning experience... Razz
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bugbrand



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PostPosted: Mon Jan 14, 2008 12:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, I actually changed the 566's rate cap (C8) to something bigger - I found the pitches generally too high with the stock 22n - I was looking for low drum tones and found you'd only have a tiny range of lows at the bottom of the pot travel. Actually, I kind of don't like the tuning response so much - its hard to tune things in the low regions...
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State Machine
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PostPosted: Mon Jan 14, 2008 5:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sounds like a couple of things going on here. The decay is very very long and the decay capacitor, C12, seems like it's not discharging completely leaving the VCA "open". Several seconds after you trigger the UD-1, there should be about zero volts across C12 decay capacitor. If not, turn the power off, turn the decay pot, R32, to minimum decay (Minimum resistance" and and measure the resistance across C12. It should be less than or equal to 1K. If not, check your connections.

As for the high frequency, without any pedal connected, the voltage across R35 should be 0V. If not, check that Q4 is not shorted from collector to emitter. Also make sure your INIT range into summing resistor R29 is from 15V down to a approximately 0.18 V. Also, check R8 and R19 values ....

OK, I will wait for your response ..........

Bill
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creatorlars



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PostPosted: Mon Jan 14, 2008 6:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Badass! Thanks so much. Got this info just as I'm sitting down to work on this thing. I'll get back with my results in a few hours.
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PostPosted: Mon Jan 14, 2008 6:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Badass! Thanks so much. Got this info just as I'm sitting down to work on this thing. I'll get back with my results in a few hours.


OK, cool. We should get this up and running for you in short order I hope. I got your e-mail also. OK, let me (us) know man ! Very Happy

I will take a peek at this thread in a bit to see how you are doing. the measurements should go quick Wink

I can always break out my UD-1 if need be, power it up and make comparative observations ...... Very Happy

OK, good luck, Bill ........
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creatorlars



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PostPosted: Mon Jan 14, 2008 7:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Several seconds after you trigger the UD-1, there should be about zero volts across C12 decay capacitor.


It's hovering at about 1.2v (when decay pot is turned to max resistance) or 1.8v (when decay pot is turned to min resistance.)

Quote:
If not, turn the power off, turn the decay pot, R32, to minimum decay (Minimum resistance" and and measure the resistance across C12. It should be less than or equal to 1K.


Ack! It's measuring about 55-60k.

Quote:
If not, check your connections.


I've triple checked all the applicable solder joints (top and bottom) i can think of, and used the meter to verify connections all around this part of the circuit... everything seems to be good. Given this new information, does the evidence point to a specific connection...?

Quote:
the voltage across R35 should be 0V.


Check. Reading 0v across R35

Quote:
make sure your INIT range into summing resistor R29 is from 15V down to a approximately 0.18 V.


Yes, I'm measuring a range of 14.85v to 0.1v

Quote:
Also, check R8 and R19 values


Resistance across R8 (supposed to be 3.9K) is ~about 3.3K, and Resistance across R19 (supposed to be 27K) is ~about 15k. I've got the right value resistors in, though -- not sure what they're supposed to read, measuring across, when in the circuit... don't think there's any way they could be bad? I'm measuring about 0.5v-2.1v (or -2.1v?) across them both.

I'm going to continue checking, just thought I'd post these results first. Let me know if you think of anything else.

Also, I noticed the parts list calls for "N.O. jacks" are these just normal jacks? I wasn't sure if there was a difference. I have a big bag of surplus panel-mount stereo 1/4" jacks I bought at the local electronics store, I think they are just standard jacks.

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PostPosted: Mon Jan 14, 2008 7:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Quote:
If not, turn the power off, turn the decay pot, R32, to minimum decay (Minimum resistance" and and measure the resistance across C12. It should be less than or equal to 1K.


Ack! It's measuring about 55-60k.


That 1.8 V is probably enough to feed current into the CA3080 and keep it "open" ........ Not good .......

OK, lets fix that first before we do anything else as attacking everything at once will not help us Very Happy . The decay pot when minimum resistance should be close to zero ohms so the only things left going to ground from C12(+) is R2, a 1K resistor. First check R2. Is it 1K ? If so, check to see the the decay pot really goes close to zero ohms by measuring with your ohm meter from the junction of R2 and R32 to ground when set to minimum. This should be close to zero ohms. If not, make sure that junction IS connected and also make sure R32 measures about zero ohms to your power supply ground .......

Bill
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creatorlars



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PostPosted: Mon Jan 14, 2008 8:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

You guys should personally come down here to Denton, Texas and kick my worthless ass!

I never connected the pot/panel/jack ground to the board ground anywhere.

Guess I saw the headers and thought I was done.... Once I connected the two grounds to each other (ground lug on output jack to ground pin on header 1) it started working perfectly.

Your last instructions totally led me to this, though. Thanks for all your time. And, now... my first synth module is working! Smile Time to wire up that populated Clangora, now...
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creatorlars



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PostPosted: Mon Jan 14, 2008 11:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

Okay, I made sure everything was securely connected and mounted it up after making a couple of the mods Bugbrand suggested in an earlier thread (added another .022 cap on top of the current one to allow for lower frequency range, and swapped the decay pot for a log 1M -- definitely like the mods.)

I'll post some sound clips/videos when I get a few more voices added.
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PostPosted: Tue Jan 15, 2008 2:54 am    Post subject: Reply with quote  Mark this post and the followings unread

Ha! Such things happen to us all!
Glad its working now.

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PostPosted: Tue Jan 15, 2008 6:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
You guys should personally come down here to Denton, Texas and kick my worthless ass!


Oh, don't ever say that man !! Very Happy I have learned the most when having to troubleshoot the mistakes i've made. Nothing beats practical hands on training with good theoretical background. I am so glad you got your first module working. Congrats and good troubleshooting with you !!!!!

I had started to think the ground was missing just by the sound of the sample you gave. The sound was meandering all over the place. The sample you posted really led to the analysis so good job !!!

I think for now on, when folks have an issue with a module, rather than describe the sound, just sample and upload it for all to hear. It really clears up lots of uncertainty and leads to the most accurate analysis. Words just lead to the wrong interpretation of a problem. "A sound is worth a 1000 words" Question .......

Quote:
Time to wire up that populated Clangora, now...


That circuit is a blast !!!!!! Good luck Very Happy

Bill
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creatorlars



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PostPosted: Tue Jan 15, 2008 9:03 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the encouragement! This is a big milestone for me. I've been planning and constructing the Midibox Sequencer and case/PSU/modules for the drum modular for about 3 months now, working on it every night -- everything hand constructed, painted, silkscreened, etc. And this is the first "finished" piece. So it's a euphoric experience... I was beginning to think I'd never have this thing done. My band is on hiatus from performing and writing until I get our new rig, ready... so the tension was killing me. Smile I'm going to hold off on a second UD1 until I finish constructing the rest of the modules I already have parts and panels for, but I think I will probably want two (or I may hold out for MPS boards instead.)

Quick question, if you don't mind -- is there a way to wire a normal stereo jack as an NC jack, so that I can do the send/return Clank/Clatter sections on the Clangora without buying new jacks? Little confused on this.
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PostPosted: Tue Jan 15, 2008 4:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Lars,

Quote:
Quick question, if you don't mind -- is there a way to wire a normal stereo jack as an NC jack, so that I can do the send/return Clank/Clatter sections on the Clangora without buying new jacks? Little confused on this.


Sure, just wire your SEND signal to the jacks "TIP" and your RETURN signal to the jacks "SLEEVE" and use an insert cable like the one shown. When you are not using the insert path, place a shorted plug into the jack. A bit clumsy but it will work. YOU can use just one single shorting jack and use it like an insert and eliminate having to plug in a shorting plug. The jack will then make the connection for you when not in use. It's called "normalizing" the connection.

Bill


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creatorlars



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PostPosted: Wed Jan 16, 2008 11:54 am    Post subject: Reply with quote  Mark this post and the followings unread

Awesome, thanks for clearing that up.

After digging around, I found some surplus stereo jacks I bought which have 5 lugs... so I can wire them with the NC option. Using a single jack wasn't an option, because I'd already finished drilling, painting and silkscreening the panel a few weeks ago. Wink

I got my 808 bass drum clone module firing last night, too. Figured out I have to send in a pulse at the Accent and Trigger inputs simultaneously. I used the NC jack option for this, too... so that when there is nothing in the Accent jack, it sends the Trigger signal to both.

I might add the TH Trigger Conditioner circuit to the 808BD input(s) to smooth things out... Slowly starting to get a much clearer mental picture on how all this shit works now. For the 808 module I need to try to figure out how to convert a constant CV at the Accent input into a 1ms pulse, triggered by a 1ms pulse at the Trigger input, prior to things going into the circuit... that way I can modulate velocity with an LFO or whatever.

Thanks again for the help. I'm really looking forward to increasing my knowledge and being able to offer help and information back to the community as soon as possible.
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PostPosted: Wed Jan 16, 2008 2:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
I need to try to figure out how to convert a constant CV at the Accent input into a 1ms pulse, triggered by a 1ms pulse at the Trigger input, prior to things going into the circuit... that way I can modulate velocity with an LFO or whatever.


Not sure I understand completely. Do you want to have a pulse ride on top of the DC going to the accent input? Like a voltage summer would do? Is my understanding off here? If you diagram it for us, maybe we can help.

Bill
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creatorlars



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PostPosted: Wed Jan 16, 2008 3:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm just thinking out loud here, I guess. Smile When I have more specific questions I will definitely come babbling at you guys again. I think what you've mentioned is what I am talking about, though.

I'll have pics and soundclips of the working modules by this weekend, I hope!
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PostPosted: Wed Jan 16, 2008 4:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
When I have more specific questions I will definitely come babbling at you guys again.


OK, standing by Very Happy

Bill
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