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Line Driver Stage on Sharp CV2133

 
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Eugbug



Joined: 15 Nov 2012
Posts: 2
Location: Ireland

PostPosted: Thu Nov 15, 2012 11:59 am    Post subject: Line Driver Stage on Sharp CV2133 Reply with quote

I have an old Sharp CV2133IR TV. The pulse input to the line driver transistor is being pulled down by a low state on the collector of a transistor in a protection circuit. This circuit seems to be connected to a winding on the LOPTR. What could cause the the circuit to operate? Is it likely to be caused by shorted windings on the transformer?
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Computech1



Joined: 14 Nov 2012
Posts: 2
Location: South Wales UK

PostPosted: Thu Nov 15, 2012 3:56 pm    Post subject: Reply with quote

Unfortunately shorted turns on a LOPTX are a common problem & can cause no line drive due to protection circuit operation. Have you disconnected the pin on the LOPTX to find out if your Line Drive returns ?
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Eugbug



Joined: 15 Nov 2012
Posts: 2
Location: Ireland

PostPosted: Thu Nov 15, 2012 5:37 pm    Post subject: Reply with quote

Computech1 wrote:
Unfortunately shorted turns on a LOPTX are a common problem & can cause no line drive due to protection circuit operation. Have you disconnected the pin on the LOPTX to find out if your Line Drive returns ?


No I didn't try that. I thought it would cause further damage if the protector circuit was disabled by disconnecting the inputs to it from the LOPTX. There seems to be 3 pins on the LOPTX connected to the protector circuit. Does the protector circuit guard against over voltage from the transformer?
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