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Line Driver Transistor on Sharp CV2133H    
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Eugbug



Joined: 13 Nov 2012
Posts: 2
Location: Ireland

PostPosted: Tue Nov 13, 2012 3:22 pm    Post subject: Line Driver Transistor on Sharp CV2133H Reply with quote

I have an old Sharp set and the line output transformer stopped working. I managed to do some tracing of the circuitry/ signals and discovered that the timebase/sync IC is outputting a pulse signal to the line driver transistor (which drives the line driver transformer and the base of the line output transistor). However the voltage is too low to turn on the transistor and seems to max out out at about 0.4 volts. I found some dry joints along the way on the resistors but unfortunately resoldering didn't make much difference. Has anyone ever worked on this set or got a schematic or any ideas what is pulling down the voltage? When I disconnect the pulse transformer form the line output transistor, the line driver stage works ok and the driver transformer generates pulses ok.
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JTS1957



Joined: 21 Jan 2009
Posts: 2325
Location: Far, Far Away

PostPosted: Tue Nov 13, 2012 9:08 pm    Post subject: Reply with quote

Is close enough perhaps?

http://elektrotanya.com/?q=showresult&what=sharp%208psr&kategoria=&kat2=all
Eugbug



Joined: 13 Nov 2012
Posts: 2
Location: Ireland

PostPosted: Wed Nov 14, 2012 4:08 am    Post subject: Reply with quote

Great! Thanks for the info and link to that site!
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