I am having a couple of problems with a philips em3e-aa.
Attatched is a trace of the h.o.t. collector voltage over the base voltage. I have been unable to find what the trace should be but i was expecting when the transistor is turned on it would be fully on dropping the Vce to virtually zero as opposed to the 80volts in this case. Its also weird to me that at the point its switched on there is not even a slight niggle in the falling voltage.
The original problem was the LOPT was arcing which i tried to bodge with some epoxy. This failed and after replacement the hot had gone taking out many other components inc p/s mosfet. Working through got Vbat back to 141v and after a short while the hot died again.
I have replaced it for a third time and now only allow it to be on for short time to get measurements. I don't know what current the hot should be carrying but at 80v every 1a is 80w which is much more than the 45w spec and would account for short life span. Also is a trace of the voltage across a 5ohm resistor in series with the lopt supply which is also unexpected. I would have expected a larger current going negative as the energy is returned. I have tested all the components around and all check out ok with multimeter (cap, diode, test res tests). It makes me wonder where all the energy is coming from to heat the hot.
If anyone can say the waveform is correct i will let it run and see what happens (presuming the hots faulty?) but if this one dies i am not buying another its the end. A shame after so much work (and cost).
I have also had to replace the video amp (tda6108jf) now the screen won't unblank. The current from pin 5 the black current measurement is around 200uA even with all the outputs disconnected. I have replaced this twice and both are giving this same reading. The spec says max leakage should be 50uA and the tv manual says the hop can manage a maximum leakage of 100uA. I have fitted a pot in this line shunting some of this current and by reducing it unblanks the set (gets retrace lines so not completely happy). I find it hard to belive two faulty components although bought same place same time if there was a bad batch? I am strugling to work on this until i can get some confidence in the hot's survival. I feel i must be missing something and would appreciate any thoughts.
Attatched is a trace of the h.o.t. collector voltage over the base voltage. I have been unable to find what the trace should be but i was expecting when the transistor is turned on it would be fully on dropping the Vce to virtually zero as opposed to the 80volts in this case. Its also weird to me that at the point its switched on there is not even a slight niggle in the falling voltage.
The original problem was the LOPT was arcing which i tried to bodge with some epoxy. This failed and after replacement the hot had gone taking out many other components inc p/s mosfet. Working through got Vbat back to 141v and after a short while the hot died again.
I have replaced it for a third time and now only allow it to be on for short time to get measurements. I don't know what current the hot should be carrying but at 80v every 1a is 80w which is much more than the 45w spec and would account for short life span. Also is a trace of the voltage across a 5ohm resistor in series with the lopt supply which is also unexpected. I would have expected a larger current going negative as the energy is returned. I have tested all the components around and all check out ok with multimeter (cap, diode, test res tests). It makes me wonder where all the energy is coming from to heat the hot.
If anyone can say the waveform is correct i will let it run and see what happens (presuming the hots faulty?) but if this one dies i am not buying another its the end. A shame after so much work (and cost).
I have also had to replace the video amp (tda6108jf) now the screen won't unblank. The current from pin 5 the black current measurement is around 200uA even with all the outputs disconnected. I have replaced this twice and both are giving this same reading. The spec says max leakage should be 50uA and the tv manual says the hop can manage a maximum leakage of 100uA. I have fitted a pot in this line shunting some of this current and by reducing it unblanks the set (gets retrace lines so not completely happy). I find it hard to belive two faulty components although bought same place same time if there was a bad batch? I am strugling to work on this until i can get some confidence in the hot's survival. I feel i must be missing something and would appreciate any thoughts.