Sharp TV dead

I have a model #27F-S120 TV that is dead. Raw B+ good to power transformer. No low voltage on primary of power up relay. I have studied the board for over an hour and simply can't see where the stand by voltage is supplied, to further troubleshoot. Hoping someone may have a schematic, or knowledge of this particular model/problem. Thankyou group as always, still a beginner here.

Reply to
Golf
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On the other side of the 'power transformer' , actually the standby transformer, you'll see 4 diodes. That's the bridge for the standby 24 volts. If that voltage isn't there, then you have an open winding in that transformer. Really common fail. If it's still available, runs around 25bucks. If not, there's other options.

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Reply to
Tech Data

Thanks asskicker, I have 120V on the primary, zero on the secondary. The way it looks though, the power on relay must energize to supply current to the transformer primary, and induce a voltage in the secondary. How is this standby transformer made/wired? Their is an IC (full bridge rectifier), on the secondary that is connected to the 24V of the relay. I trust your info, just don't fully understand. Thanks again techdata.

Reply to
Golf

Ok, to cut it short, the ac line in goes straight to the primary of that transformer. That alone energizes the windings to induce the 24 volt standby source which also goes to the relay, as well as the 12,9 and 5 volt lines. When the relay latches, THEN ac is routed to the primary of the swithcing power supply that provides the B+ for the horizontal circuit. Without the smaller standby transformer working, NOTHING else is going to work. To prove or disprove, use an ohm meter and measure resistance on the two secondary pins of that transformer. I got a buck says they're open. Should read shorted or near shorted. There may or may not be a thermal fuse inside the transformer but, the way that's designed, you'll destroy it before you get to it. Best to replace.

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Reply to
Tech Data

transformer designs. If it is designed to induce a voltage into the secondary (on standby power), does the primary have a interal closed loop, that induces this 24 volts into the secondary? The circuit reveals an open on the primary from the outside. Thanks a ton techdata for the response.

Reply to
Golf

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