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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Requesting Help with MFOS 10 Step Sequencer
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tehskull



Joined: May 07, 2011
Posts: 23
Location: Kentucky
Audio files: 1

PostPosted: Sat May 07, 2011 7:34 pm    Post subject: Requesting Help with MFOS 10 Step Sequencer
Subject description: MFOS 10 step sequencer with MFOS wall wart power supply
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Hello Everyone. I am new to the forum and this is my first post. I am seeking some advise. I have been working for the last month on a MFOS 10 step sequencer. It is being powered with a MFOS wall wart power supply using a 12VAC 1000ma wall wart. The problem that I am having is that the unit is not functioning at all. Start/stop and manual step is not having any effect on the unit. I have gone as far as replacing all of the ICs and have even bread boarded it to eliminate issues with panel wiring. I have included pictures of the circuit board and of the panel wiring in hopes that one of you can see something that I am missing. The only symptom that happens when the unit is powered on is that the 4013 gets very hot almost instantly. Note, all parts and values are what are specified on Ray's site. Also all resistors are 1/4 watt 1%. Thanks in advance for anyone that can help. PS please excuse the messy panel wiring. This will be cleaned up when its up and running.


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Populated circuit board not connected.
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Circuit board connected.
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Panel Wiring.
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Front panel. I just look at this when I am down from troubleshooting it :)
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bubzy



Joined: Oct 27, 2010
Posts: 535
Location: United Kingdom
Audio files: 50

PostPosted: Sat May 07, 2011 11:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

its definately worth checking your power supply, make sure you have the + and - the correct way around. cmos chips are very sensitive to polarity. the other possibility is that you have a short circuit somewhere, or a power connection to ground athough this may cause different issues.

it looks like you have done a nice job on the circuit board, and dont worry about the panel wiring, i cringe everytime i see my wiring and almost give up hope when i have to troubleshoot it Very Happy

Welcome to electro-music, if my answer doesnt help there are plenty of people here who actually KNOW what they are talking about Smile
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kkissinger



Joined: Mar 28, 2006
Posts: 1212
Location: Kansas City, Mo USA
Audio files: 29

PostPosted: Sun May 08, 2011 7:41 am    Post subject: Reply with quote  Mark this post and the followings unread

To elaborate on bubzy's reply:

First of all, congratulations on building your sequencer and excellent that you identified a part that is too hot.

The reason that a part overheats is that it is being forced to conduct too much current. This suggests a short and is quite likely to be a solder bridge. I would first look for a solder bridge in the vicinity of the chip. You may wish to use a continuity tester to assure that adjacent traces are not shorted out -- all it takes is a nearly-microscopic amount of solder to create a bridge.

Note that the circuit only uses 1/2 of the 4013 chip. Make sure that pins
7 through 11 are all connected to ground. Make double sure they are not connected to the -12 volt supply.

If that all checks out, and you didn't find a solder bridge, then there is likely a short "downstream" of the chip. If you socketed the chip, you can carefully pull it out and using a needle-nose, carefully bend selected legs of the chip such that you can plug the chip in with the selected leads outside the socket.

For starters, bend out pin 1, then see if the chip overheats. If it does then you want to check D17 (make sure its polarity is correct) and check to see if have the correct values for R35 and R85. Also, look for solder bridges in the vicinity of those parts.

If the chip does not overheat with pin 1 removed, then the problem is off of pin 1 -- for starters, check the polarity of D23.

In looking at the schematic, the clock may run without the 4013 chip in place -- give it a try and see if the clock runs.

Hope this helps.

(edit: also, with the 4013 chip removed, see if the manual step switch works -- it should work without the 4013 chip.)

_________________
-- Kevin
http://kevinkissinger.com
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tehskull



Joined: May 07, 2011
Posts: 23
Location: Kentucky
Audio files: 1

PostPosted: Sun May 08, 2011 12:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks to all for the advise. I am going to try your recommendations and let you know how it goes. Have a great day!
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tehskull



Joined: May 07, 2011
Posts: 23
Location: Kentucky
Audio files: 1

PostPosted: Sun May 08, 2011 3:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

Success!!! Well Sort of. Everything is working now except for step 6. Back to the workshop to get this thing going 100%.
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