Author |
Message |
Appliancide*
Joined: Jul 04, 2007 Posts: 126 Location: Paul lives in a 1920’s film
|
Posted: Tue Apr 23, 2013 5:22 pm Post subject:
SN Voice - 3rd time is a char...uhh, problem Subject description: problem solved!!! |
|
|
I have run into a bit of a puzzler on the third SN Voice I've built. Actually two problems, but I'm wondering if they are related.
First, the triangle out is weak. The LFO output and pulse/noise output are both putting out the expected levels. I have been using my scope to eyeball levels and compare them to one of my working units, so please forgive the lack of specific numbers. The output amplifier/buffer seems to be working fine. The triangle just seems to be weaker coming out of the 76477. I checked R51 to make sure it was 220k.
Second, the PWM is not working at all. There is no variation between the switch settings. I triple-checked my switch wiring, doing continuity tests on the PCB itself to rule out the MTA connectors.
I know this circuit has been around for quite a while, so I'm curious if anyone has had similar problems, or maybe ideas about mine. _________________ http://appliancide/blogspot.com Last edited by Appliancide* on Thu May 16, 2013 4:48 pm; edited 1 time in total |
|
Back to top
|
|
|
sneakthief
Joined: Jul 24, 2006 Posts: 569 Location: Berlin
|
Posted: Wed Apr 24, 2013 3:10 am Post subject:
|
|
|
Sorry to be Mr. Obvious, but did you try swapping out the SN for another known working one? _________________ Sneak-Thief - raw electrofunk |
|
Back to top
|
|
|
Appliancide*
Joined: Jul 04, 2007 Posts: 126 Location: Paul lives in a 1920’s film
|
Posted: Wed Apr 24, 2013 8:26 am Post subject:
|
|
|
I will have to check to see if I have a "known good" wide version. My two working versions have the narrow chips in them.
Has anyone ever come across a partially working SN76477? I ask because most of the functions tied to that chip seem to be working (noise, lfo, envelope, mixer....). _________________ http://appliancide/blogspot.com |
|
Back to top
|
|
|
Appliancide*
Joined: Jul 04, 2007 Posts: 126 Location: Paul lives in a 1920’s film
|
Posted: Wed Apr 24, 2013 6:01 pm Post subject:
|
|
|
I did have another wide one to check and the behavior was the same, so I must have made a mistake somewhere. I feel like the answer is staring me in the face, especially since there is very little circuitry associated with the functions I am having problems with. _________________ http://appliancide/blogspot.com |
|
Back to top
|
|
|
Appliancide*
Joined: Jul 04, 2007 Posts: 126 Location: Paul lives in a 1920’s film
|
Posted: Fri Apr 26, 2013 12:41 pm Post subject:
|
|
|
I broke down and pulled one of my working modules out of the case to switch pcbs with the problem module.
The working pcb has no problems when connected to the newest module's faceplate, so I can now say that my wiring is not at fault.
I really wish that I enjoyed troubleshooting more. _________________ http://appliancide/blogspot.com |
|
Back to top
|
|
|
Uncle Krunkus
Moderator
Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
Audio files: 52
G2 patch files: 1
|
Posted: Fri Apr 26, 2013 2:36 pm Post subject:
|
|
|
I hardly ever enjoy troubleshooting while it's happening. But the payoff can be very satisfying. Good luck with it. _________________ What makes a space ours, is what we put there, and what we do there. |
|
Back to top
|
|
|
Appliancide*
Joined: Jul 04, 2007 Posts: 126 Location: Paul lives in a 1920’s film
|
Posted: Tue Apr 30, 2013 1:17 pm Post subject:
|
|
|
I had two pcbs that I stuffed 4-5 years ago that I was going to build in a format that I've since abandoned. I dug one out, cleaned it up a little bit and it works. I used the same sn76477 from the problem module, so that wasn't the problem.
I though that J3-2 and J3-3 might have been interacting in some way on the problem PCB, so I decided to wick some solder off of those pads in case there was a small short under the J3 header. When I did this, it exposed some copper on the little triangular section between the two pads (this is one of the newest PCBs). It isn't shorted to either jumper, but i can't help thinking it could have been causing problems. I wonder if I could have damaged the PCB when I was cleaning the flux off. I used a pretty strong flux remover, so maybe some seeped into the PCB? I can only guess at this point, since I was never able to definitively nail down the problem.
Now that I have two working modules again (third one was for a forum friend, so I just gave him one of mine while I was troubleshooting this one), I will probably de-solder the expensive parts and chuck it in my failure box to mess with another day. _________________ http://appliancide/blogspot.com |
|
Back to top
|
|
|
Appliancide*
Joined: Jul 04, 2007 Posts: 126 Location: Paul lives in a 1920’s film
|
Posted: Thu May 16, 2013 4:46 pm Post subject:
|
|
|
Holy cow, am I a moron! After thinking the old board I swapped in fixed the problem, I noticed the same problems again!
It wasn't the SN chips I tried and it wasn't the pcbs themselves. I also had the same problem with two different panels, so what is the difference between the working modules and the "problem" modules?
Freakin' trimpots! On my first two modules, I used single-turn pots for the offset and modulation adjustments. The modules with the "problem" both have multi-turn pots, that I failed to take through their full ranges before moving to troubleshooting.
I will spare you the details of all of the different things I tried before realizing this. I just wanted to wrap this thread up with a solution instead of the the defeat I expressed in the last post.
It's embarrassing to post this, but maybe it will be a reminder to someone else down the road that sometimes it's best to walk away and come back with a clear head. Obvious solutions are very good at hiding from frustrated people! _________________ http://appliancide/blogspot.com |
|
Back to top
|
|
|
Danno Gee Ray
Joined: Sep 25, 2005 Posts: 1351 Location: Telford, PA USA
|
Posted: Thu May 16, 2013 4:57 pm Post subject:
|
|
|
We appreciate your candor, and allowing us all tou learn with you from your journey. Do not feel alone in having traveled there.
Congratulations on finding the error yourself. |
|
Back to top
|
|
|
elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
Audio files: 16
|
Posted: Thu May 16, 2013 6:34 pm Post subject:
|
|
|
Hooray for working SN Voice |
|
Back to top
|
|
|
Wobuse
Joined: Dec 07, 2011 Posts: 34 Location: Lyons,il
|
Posted: Sun May 19, 2013 12:32 am Post subject:
|
|
|
Danno Gee Ray wrote: | We appreciate your candor, and allowing us all tou learn with you from your journey. Do not feel alone in having traveled there.
Congratulations on finding the error yourself. |
I second that!
Everyone makes so called silly mistakes, but we only learn from our mistakes...
even silly ones. _________________ "It's nice 2 B important; but it's important 2 B nice"
Visit my studio ; LimeStoneLabs at: www.Facebook.com/LSlabs
Hear some of my sound track work ,on the web series ,, www.cafegangster.com/16
https://soundcloud.com/james-phillips-75 |
|
Back to top
|
|
|
|