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Daewoo CP775 failure due to replaced deflection transistor

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Mazz

Mazz

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Hi
after replacing the 2SD1880 horizontal deflection transistor with one ST2310DHI (equivalent one), the transistor dies just after replacent (BCE becomes short circuit). Any suggestion on what could be the reason?

Thanks a lot.
Mazz
 

equivallent st2310 dhi

Maybe some broken joints exist.Try to check the joints around FBT.

GOOD LUCKY
Su-36
 

cp-775 fbt

What do you mean with "broken joints"?
If you mean pcb solder they are ok.
Also inside the FBT (transformer) it seems there is no open circuit. But I'm not sure because schematic is not really clear about the windings of the transformer.
But what about a short circuit in the FBT? How to check it?

Thanks
Mazz
 

the reasons of daewoo failure

Hi,Mazz
First,please check the pcb solder joints which is around flying back transformer carefully.If broken solder joints exist,it will make pluse with very high voltage,this phenomenon will destroy H deflection transistor.
I suppose the FBT is ok.because monitor have complete protection circuits.If your FBT is bad,the H voltage will lose but D1880 will be ok.
And if you use other transistor ,you must notice its Ft,Ic,Icpulse and P.Otherwise it will go bad.Another suggest:try to detect the power supply for H delfection and check the capacitors which are connected to the c and e of H deflection transistor.I guess that the cap has failed or reduced in value.
Su_36
 

Re: Daewoo cp775 failure

Su_36

powering on the TV with CRT H & V inductors disconnected the TV is OK.
When I connect the H inductor immediately some flashes appears inside the transformer and after some seconds the bjt dies.

I think the tranformer has failed. The other possibility is that the CRT inductor is in short circuit.

How these parts can be tested?

thanks
Mazz
 

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