Proview blown primary

[Behemot]

Got only the board, found rotten input capacitor with blown primary side (found bad transistor, rectifier, MOX resistor and fuse). Replaced all of it (FQPF7N80C for 2SK3264, 0R36 resistor for 0R22), with bulb in series the bulb shines like hell and I got almost no voltage on input cap. I got very low resistance over C206 which seems to be filtering VCC for LD7575. The diode there tested fine alone so either bad transformer, or LD7575? Or may it be something else?

[budm]

Re: Proview blown primary

The SMPS IC 201 may be damaged when the MOSFET blown up, it drive output may stuck HIGH so the MOSFET is not switching on and off like it should. You can try check the resistance of the IC between the ground pin against all the pin, and VCC pin against all the pin.

[Behemot]

Re: Proview blown primary

GND to:
RT 660R
COMP 885R
CS 790R
HV 686R
VCC ~0
OUT 790R

VCC to:
RT 883R
COMP 883R
CS 792R
GND ~0
HV 682R (infinity the other way)
OUT 1786R

[budm]

Re: Proview blown primary

The VCC to Out (Gate drive) seems low to me, I expect it to be in K Ohm range. You can lift the drive pin off the board. and see if the lamp will still light up bright and stay on bright.

[Behemot]

Re: Proview blown primary

Still full on. I guess this one is good to go…

[viziks]

Re: Proview blown primary

Check Bridge BD201 and confirm polarity +,-, ~,~ sequence,also C201 and FET 7N80 again.0.36ohms may not work and cause shutdown at full load.

[Behemot]

Re: Proview blown primary

I removed the LD7575, somewhat damaged the paths but it is not shorted now so it was it. I also found practically the same problem with same board from different display, there was also the driver bad.

Schematic here http://www.ebastlirna.cz/modules/For...isplej_135.jpg

Will probably try to get it from eBay and somehow fix the bloody mess I did there with 150W transformer iron Well, can always connect tiny wires to the legs instead of the burned paths

[budm]

Re: Proview blown primary

I always replace the IC along with the MOSFET when the MOSFET is damaged, you are lucky since you have the lamp connected to protect it from blowing up the new MOSFET.

[Behemot]

Re: Proview blown primary

Replaced IC, still nothing so I'll ditch it for parts…