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1992 Toshiba CN3081B Cinema Series

 
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massimo



Joined: 09 Apr 2008
Posts: 5

PostPosted: Wed Apr 09, 2008 2:35 pm    Post subject: 1992 Toshiba CN3081B Cinema Series Reply with quote

Hi

I have an old Toshiba CN3081B Cinema Series and it has been inactive for the past 3 years. Last time it was turned on, it started to show a problem where, as it warms up, it would start loosing the vertical sync to the point that the screen will be reduced to one horizontal line. I have taken the back panel out and located the vertical circuit but without a schematic it is hard to see what I am looking at. No components show visible failure, that I can tell. Just wondering if anybody else had the same problem and if anybody has any schematic regarding this TV or at least where I could find one.

Thanks in advance

Massimo
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minnie



Joined: 18 Aug 2005
Posts: 2877
Location: Hell

PostPosted: Fri Apr 11, 2008 11:24 pm    Post subject: Reply with quote

The vertical IC will start with LA78##. Usually the 100uf 50vdc cap next to it. I'd replace all the caps around it.
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massimo



Joined: 09 Apr 2008
Posts: 5

PostPosted: Wed Apr 16, 2008 2:32 pm    Post subject: Reply with quote

Thank you for the info
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massimo



Joined: 09 Apr 2008
Posts: 5

PostPosted: Wed Jun 10, 2009 4:39 am    Post subject: 1992 Toshiba CN3081B Cinema Series Reply with quote

Well, here I am again with the same problem . I have replaced the IC LA7837 and the 100uF and 220uF Caps that are filtering the 2 supplies for the IC, 9V and 24V. The 24V measured 28V and I am not sure if this is still within spec. Also I have replaced all other electrolytic caps around the IC with no success. I have found the datasheet for the LA7837 ( http://pdf1.alldatasheet.com/datasheet-pdf/view/40354/SANYO/LA7837.html ). I can only troubleshoot the circuit when the unit is off because I do not have the proper cable extensions to perform any troubleshooting when the tv is on

Any other suggestions?

Thank you again

Massimo Sad
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minnie



Joined: 18 Aug 2005
Posts: 2877
Location: Hell

PostPosted: Wed Jun 10, 2009 11:27 pm    Post subject: Reply with quote

Follow the flyback, there should be a diode feeding the IC.
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massimo



Joined: 09 Apr 2008
Posts: 5

PostPosted: Tue Jun 16, 2009 3:09 am    Post subject: 1992 Toshiba CN3081B Cinema Series Reply with quote

Hi Minnie

I am not sure what you mean by flyback and which diagram are you referring to? The only diode is the one connected to 24V and a cap connected to pin 9.

Thanks Smile
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minnie



Joined: 18 Aug 2005
Posts: 2877
Location: Hell

PostPosted: Wed Jun 17, 2009 1:45 am    Post subject: Reply with quote

The flyback has the high voltage lead coming out of it.
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massimo



Joined: 09 Apr 2008
Posts: 5

PostPosted: Tue Oct 06, 2009 2:10 am    Post subject: 1992 Toshiba CN3081B Cinema Series Reply with quote

Hi, sorry it took me so long to reply.I have checked the diode connected to the flyback transformer and it is good...I am trying to figure it out how this diode is important to the problem that I am having.

Thanks
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minnie



Joined: 18 Aug 2005
Posts: 2877
Location: Hell

PostPosted: Thu Oct 08, 2009 10:52 pm    Post subject: Reply with quote

The diode provides the voltage to the vertical ic.
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