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Hitachi Television Dead
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PostPosted: Sun Jan 16, 2011 6:42 pm    Post subject: Reply with quote

DCU SW-7V (-18.65V) is high, but is it? When I trace the path of SW-7V on the wiring diagram to convergence board (page 106) to QK01, it shows needing -7volts but QK01s working voltage (page 95) is -26.8volt on the emitter. There is a contradiction of wiring diagram or misprint.

PPD3 disconnected - the television comes on with all LEDs on and with sound but no raster.

PPD5 disconnected - all LEDs on power supply come on only with no sound and no raster
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jts1957



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PostPosted: Sun Jan 16, 2011 7:32 pm    Post subject: Reply with quote

What's on its collector?
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beertap



Joined: 04 Jan 2011
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PostPosted: Sun Jan 16, 2011 8:58 pm    Post subject: Reply with quote

With both STKs still out and everything else connected, the voltage on the collector of QK01 is (-5.3v) and should be 0.1v according to page 95 of schematics. The base is -19.1v and emitter -18.65v.
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beertap



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PostPosted: Mon Jan 17, 2011 4:15 am    Post subject: Reply with quote

I have finally Isolated it to one circuit (V. BLK) When I remove (V. BLK) going to the signal board via PPS3 connector the TV will come on and play nicely. Now, I have to find the bad component(s) in this circuit. I will report my findings in another post.
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jts1957



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PostPosted: Mon Jan 17, 2011 5:37 am    Post subject: Reply with quote

jts1957 wrote:
I'd confirm that all power supply secondaries are trying to come up and that there is no other heavy loads stopping them. Also regulator failures.
What happens IF you were to keep the relay energized? (either by putting a jumper or your own voltage to driver) Micro might not be receiving horiz or vertical sample and shutting set down.


I wonder?
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beertap



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PostPosted: Tue Jan 18, 2011 1:33 am    Post subject: Reply with quote

What type of signal should I be seeing on the flyback generator (pin 11) located on vertical deflection chip? I'm thinking saw tooth but not sure.
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beertap



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PostPosted: Wed Jan 19, 2011 2:07 am    Post subject: Reply with quote

I've narrowed the problem down to this chip "Vertical Deflection Circuit" part# TDA8174A. I am having a problem locating it. Any ideas?
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jts1957



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PostPosted: Wed Jan 19, 2011 2:52 am    Post subject: Reply with quote

Locating it in the set or for purchase?
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jts1957



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PostPosted: Wed Jan 19, 2011 3:01 am    Post subject: Reply with quote

http://audiolabga.com/mal_cart/mal_cart.php?find=TDA8174A&gclid=CK6Xn8OixaYCFc9J2godo0OUIQ

Deflection PCB On heat sink behind flyback transformer
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beertap



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PostPosted: Wed Jan 19, 2011 4:47 am    Post subject: Reply with quote

Sorry for the confusion. I was looking for a source for the part and of course you provided it. Thanks. Also, could there be anything else that goes to this chip that would cause my problem? I ask because I think that there might be another input which might be missing and I'm not sure how the flyback generator (pin 11) works.
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