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mistu no vert. (thin blue horizontal line mid-screen)    
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brandonsdad



Joined: 23 Jul 2010
Posts: 6
Location: eternal hell

PostPosted: Fri Jul 23, 2010 10:57 am    Post subject: mistu no vert. (thin blue horizontal line mid-screen) Reply with quote

I have a 35" mitsubishi (i'm guessing by the model no.)
CS-35401
1993

so i've read the tutorials and i have the shroud off and the CRT discharged. I'm just not really sure where to locate the IC to be resoldered or even inspected. I'm definitely not a TV repair guy but im smart and willing enough to listen, learn and fix this big heavy monster (after all times are tough.)

any and all insight, help or hints would be greatly appreciated! i hate even bothering after having read all the success stories in the forums but it seems mostly every make/model is different and im stuck.
thanks again,
brandons dad
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JTS1957



Joined: 21 Jan 2009
Posts: 2328
Location: Far, Far Away

PostPosted: Fri Jul 23, 2010 11:43 am    Post subject: Reply with quote

Mounted on a heat sink at location IC401 will be an IC chip with the number LA7838 printed on it. If the solder joints are good the IC is likely bad.
Here is datasheet for it. Also make sure it has approximately 12 volts on pin 1 and 24 volts on pin 8.
http://www.alldatasheet.com/datasheet-pdf/pdf/40355/SANYO/LA7838.html
brandonsdad



Joined: 23 Jul 2010
Posts: 6
Location: eternal hell

PostPosted: Fri Jul 23, 2010 1:01 pm    Post subject: Reply with quote

Thanks JTS. I DID manage to find the right circuit and part, but i also maged to discover that i probably don't have the right tools. i think my solder AND the iron tip are just a little too big, and its hard to determine bad joints w/o a magnifying glass. Anyways i attempted soldering one connection that looked questionable, put it back together, plugged it in and still a blue line.

I think for today i'll retreat, regroup and re-approach tomorrow. thanks again for your help- would've been nice to give you good news though Neutral
JTS1957



Joined: 21 Jan 2009
Posts: 2328
Location: Far, Far Away

PostPosted: Fri Jul 23, 2010 4:51 pm    Post subject: Reply with quote

Do you have a DVM and measure those two voltages?
brandonsdad



Joined: 23 Jul 2010
Posts: 6
Location: eternal hell

PostPosted: Fri Jul 23, 2010 6:27 pm    Post subject: Reply with quote

nope. should have a multimeter but i don't. im guessin' thats a good place to start huh?
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brandonsdad



Joined: 23 Jul 2010
Posts: 6
Location: eternal hell

PostPosted: Fri Jul 23, 2010 6:33 pm    Post subject: Reply with quote

if the voltage is not what it should be then does that mean the power supply? sorry if im irritating i think im more curious than anything at this point. i want to know just how a tv works. there's always been a way throughout what i've done as far as work history but this is a whole new ballgame, and well, im very intrigued besides wanting my tv to work again.
JTS1957



Joined: 21 Jan 2009
Posts: 2328
Location: Far, Far Away

PostPosted: Fri Jul 23, 2010 7:59 pm    Post subject: Reply with quote

Hypothetically, lets say the vertical output IC went belly-up (due to bad solder joints or old age, take your pick). When it did one or both b-plus sources were stressed causing one supply to fail. Usually just a surge (fusible) resistor is taken out, but sometimes that source's rectifier goes along for the ride. Cool
brandonsdad



Joined: 23 Jul 2010
Posts: 6
Location: eternal hell

PostPosted: Fri Jul 23, 2010 8:39 pm    Post subject: Reply with quote

would the fact that it worked before it was moved to my house make a difference? also, it sounds like i was @ least in the ballpark on my guess.
JTS1957



Joined: 21 Jan 2009
Posts: 2328
Location: Far, Far Away

PostPosted: Fri Jul 23, 2010 10:59 pm    Post subject: Reply with quote

Worked before move ... no vertical deflection after move. Set down hard, bounced, balanced on a pointy wrought iron fence post? Now you're probably talking physical damage. Maybe a cracked foil near flyback transformer?
brandonsdad



Joined: 23 Jul 2010
Posts: 6
Location: eternal hell

PostPosted: Sat Jul 24, 2010 11:04 am    Post subject: Reply with quote

no never set down hard as far as i know and was packed very well for transit but a few bumps in the road could've been a factor i guess.
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