Legato 3.1 - No output Options  Watch this topic  Print this topic  Atom Feed  RSS Feed View » Normal Threaded

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free2dev		#1 Posted : Monday, January 2, 2012 11:51:48 PM(UTC)
Rank: Advanced Member Groups: Member Joined: 5/19/2010(UTC) Posts: 66 Location: California, USA		Hello, I recently purchased the Legato 3.1 kit. When I powered on I could not see any voltage swing on both BAL and SE outputs while adjusting the VRs. I am not using the buffer and J5/J6 has been populated. When I connected the source, there was no output on the SE outputs. What could be the problem and where to start the debugging? Thanks, Subbu
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free2dev		#2 Posted : Tuesday, January 3, 2012 6:09:52 PM(UTC)
Rank: Advanced Member Groups: Member Joined: 5/19/2010(UTC) Posts: 66 Location: California, USA		Anyone experienced this kind of issue before? I am going to inspect and re-solder tonight. Any critical areas to monitor the voltages, etc would be helpful to find out the cause. Thanks! Subbu
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free2dev		#3 Posted : Tuesday, January 3, 2012 11:28:26 PM(UTC)
Rank: Advanced Member Groups: Member Joined: 5/19/2010(UTC) Posts: 66 Location: California, USA		Update: Checked the board again and re-soldered all the joints, still the same result. I set my multimeter to 200mV range and was able to see some voltage swing on the differential outputs. Set it to 0 volt. But the SE outputs did not respond to the VR changes and no output when I connect the source. Please help!
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Russ White		#4 Posted : Wednesday, January 4, 2012 5:56:07 AM(UTC)
Rank: Administration Groups: Administration, Customer Joined: 10/24/2006(UTC) Posts: 3,979 Location: Nashville, TN Thanks: 25 times Was thanked: 89 time(s) in 83 post(s)		Pictures will help.
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free2dev		#5 Posted : Wednesday, January 4, 2012 9:42:24 AM(UTC)
Rank: Advanced Member Groups: Member Joined: 5/19/2010(UTC) Posts: 66 Location: California, USA		Hello Russ, Here are the pictures. Thanks, Subbu free2dev attached the following image(s): Legato 3.1 01.jpg (192kb) downloaded 120 time(s). Legato 3.1 02.jpg (176kb) downloaded 125 time(s). Legato 3.1 03.jpg (188kb) downloaded 120 time(s). Legato 3.1 04.jpg (174kb) downloaded 120 time(s). You cannot view/download attachments. Try to login or register.
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avr300		#6 Posted : Wednesday, January 4, 2012 11:50:38 AM(UTC)
Rank: Member Groups: Member Joined: 6/17/2008(UTC) Posts: 921 Thanks: 1 times Was thanked: 70 time(s) in 69 post(s)		Can you hear the relay engage (click) upon power-up ? Further, what are your supply voltages ?
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free2dev		#7 Posted : Wednesday, January 4, 2012 11:58:00 AM(UTC)
Rank: Advanced Member Groups: Member Joined: 5/19/2010(UTC) Posts: 66 Location: California, USA		Hi avr300, Yes I can hear the relay click upon power up and I am supplying the board with +/- 13.5 volts from LCBPS. The resistors are warm after few mins of running. Thanks, Subbu Edited by user Wednesday, January 4, 2012 11:58:42 AM(UTC)  | Reason: Not specified
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Russ White		#8 Posted : Wednesday, January 4, 2012 1:54:01 PM(UTC)
Rank: Administration Groups: Administration, Customer Joined: 10/24/2006(UTC) Posts: 3,979 Location: Nashville, TN Thanks: 25 times Was thanked: 89 time(s) in 83 post(s)		You need to install R25 and R26. Or jumper them.
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avr300		#9 Posted : Wednesday, January 4, 2012 2:14:22 PM(UTC)
Rank: Member Groups: Member Joined: 6/17/2008(UTC) Posts: 921 Thanks: 1 times Was thanked: 70 time(s) in 69 post(s)		Looking at my own Legato here - is it a +2 layer board Russ ?
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free2dev		#10 Posted : Wednesday, January 4, 2012 2:43:10 PM(UTC)
Rank: Advanced Member Groups: Member Joined: 5/19/2010(UTC) Posts: 66 Location: California, USA		Russ, I will install the resistors tonight and check it out. Misread the manual which said optionally install L1/L2 for the buffer. Thanks, Subbu
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Russ White		#11 Posted : Wednesday, January 4, 2012 2:52:55 PM(UTC)
Rank: Administration Groups: Administration, Customer Joined: 10/24/2006(UTC) Posts: 3,979 Location: Nashville, TN Thanks: 25 times Was thanked: 89 time(s) in 83 post(s)		Yep the Ls are optional, the Rs are not. :)
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Russ White		#12 Posted : Wednesday, January 4, 2012 2:53:54 PM(UTC)
Rank: Administration Groups: Administration, Customer Joined: 10/24/2006(UTC) Posts: 3,979 Location: Nashville, TN Thanks: 25 times Was thanked: 89 time(s) in 83 post(s)		avr300 wrote: Looking at my own Legato here - is it a +2 layer board Russ ? It's 2 layers. A quick look at the schematic will highlight the poster's issue.
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free2dev		#13 Posted : Wednesday, January 4, 2012 11:35:42 PM(UTC)
Rank: Advanced Member Groups: Member Joined: 5/19/2010(UTC) Posts: 66 Location: California, USA		Hello Russ, Adding the resistors solved the problem. Thanks! Subbu
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