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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Troubleshooting Ultimate Repeat Gate
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JanneI



Joined: Oct 19, 2015
Posts: 18
Location: Finland
PostPosted: Mon Oct 19, 2015 2:08 am    Post subject: Troubleshooting Ultimate Repeat Gate Reply with quote  Mark this post and the followings unread
Hi all!

I just finished my first diy synth project, ultimate+expander. Everything seems to work fine, except the repeat gate.

1) IC oscillates as should, I checked with an oscilloscope as described in the mfos troubleshooting docs
2) I checked the parts and wiring, everything is as should

What it does is... on a high gate all 3 oscillators detune downwards tiny bit and there's also a noticeable ground loop -type of sound. At low gate (0v) everything goes back to normal. Really annoying.. :-/

Any ideas what could solve this? I really like the synth otherwise!

Cheers,
Janne

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blue hell
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Joined: Apr 03, 2004
Posts: 24670
Location: The Netherlands, Enschede
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PostPosted: Mon Oct 19, 2015 5:59 am    Post subject: Re: Troubleshooting Ultimate Repeat Gate Reply with quote  Mark this post and the followings unread
welcome Janne

JanneI wrote:
What it does is... on a high gate all 3 oscillators detune downwards tiny bit and there's also a noticeable ground loop -type of sound. At low gate (0v) everything goes back to normal.


Sounds like there is a short but only when the gate is active .. or at least something drawing too much current then.

What does the power supply look like on the scope with the gate high?
_________________
Jan
also .. could someone please turn down the thermostat a bit.
Posted Image, might have been reduced in size. Click Image to view fullscreen.
9 3 4 .. erm .. not 13 then? .. hmm, ah eight! .. yeah yeah as in 8647 .. 47 is an 88 .. pwew .. numbles!
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prgdeltablues



Joined: Sep 25, 2006
Posts: 222
Location: UK
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PostPosted: Mon Oct 19, 2015 8:08 am    Post subject: Reply with quote  Mark this post and the followings unread
It sounds like that to me too. Try checking you've got the correct values for R220 and R279, and that you haven't got shorts around those.

Peter
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elmegil



Joined: Mar 20, 2012
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PostPosted: Mon Oct 19, 2015 9:17 pm    Post subject: Reply with quote  Mark this post and the followings unread
Definitely sounds like something is loading your supply too much. You don't mention what you're using....
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JanneI



Joined: Oct 19, 2015
Posts: 18
Location: Finland
PostPosted: Mon Oct 19, 2015 11:51 pm    Post subject: Reply with quote  Mark this post and the followings unread
elmegil wrote:
Definitely sounds like something is loading your supply too much. You don't mention what you're using....


I use Ray's Wall Wart power supply with lm7812/lm7912 and 12vac 500mA wall wart. Should I try 1000mA wall wart instead? I didn't find exact info on current demands for ultimate+expander combo on mfos website.

Thanks all for helping me out!

Cheers,
Janne
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JanneI



Joined: Oct 19, 2015
Posts: 18
Location: Finland
PostPosted: Tue Oct 20, 2015 5:41 am    Post subject: Reply with quote  Mark this post and the followings unread
I bought a 12vac 1000mA wall wart and voila! Problem solved!

At first I used Ray's adjustable ac/dc with a 18,5vac x2 0,62a wall wart without problems, but when I boxed the synth I switched the power. Mistakes, best way to learn Wink

Thanks all for helping me! Sometimes it's hard to know where to look if you're a newbie like me Wink

Cheers,
Janne
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elmegil



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PostPosted: Tue Oct 20, 2015 5:45 am    Post subject: Reply with quote  Mark this post and the followings unread
Great news. Probably a good idea to still check those resistor values though...
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JanneI



Joined: Oct 19, 2015
Posts: 18
Location: Finland
PostPosted: Tue Oct 20, 2015 6:44 am    Post subject: Reply with quote  Mark this post and the followings unread
elmegil wrote:
Great news. Probably a good idea to still check those resistor values though...


Yes, I checked all the components, everything seems to work as should! Thanks!

Fun to play with this even without a keyboard! Next step, keyboard controller! Smile
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blue hell
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Joined: Apr 03, 2004
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Location: The Netherlands, Enschede
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PostPosted: Tue Oct 20, 2015 7:14 am    Post subject: Reply with quote  Mark this post and the followings unread
Ah ok. could have been just on the edge with the power supply .. glad you found it :-)
_________________
Jan
also .. could someone please turn down the thermostat a bit.
Posted Image, might have been reduced in size. Click Image to view fullscreen.
9 3 4 .. erm .. not 13 then? .. hmm, ah eight! .. yeah yeah as in 8647 .. 47 is an 88 .. pwew .. numbles!
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JanneI



Joined: Oct 19, 2015
Posts: 18
Location: Finland
PostPosted: Tue Oct 20, 2015 1:02 pm    Post subject: Reply with quote  Mark this post and the followings unread
Blue Hell wrote:
Ah ok. could have been just on the edge with the power supply .. glad you found it Smile


https://www.youtube.com/watch?v=KzjSBebi1TA Wink
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blue hell
Site Admin


Joined: Apr 03, 2004
Posts: 24670
Location: The Netherlands, Enschede
Audio files: 330
G2 patch files: 320
PostPosted: Tue Oct 20, 2015 1:31 pm    Post subject: Reply with quote  Mark this post and the followings unread
Cool
_________________
Jan
also .. could someone please turn down the thermostat a bit.
Posted Image, might have been reduced in size. Click Image to view fullscreen.
9 3 4 .. erm .. not 13 then? .. hmm, ah eight! .. yeah yeah as in 8647 .. 47 is an 88 .. pwew .. numbles!
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JanneI



Joined: Oct 19, 2015
Posts: 18
Location: Finland
PostPosted: Thu Oct 22, 2015 10:36 am    Post subject: Reply with quote  Mark this post and the followings unread
One more Smile

https://www.youtube.com/watch?v=slkRK8cYbY0
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