My 5th day working on this Panasonic PT-L735E projector. I'm beginning to feel worthless and like such a loser. When i first got the unit it would power up but the lamp wouldnt turn on. It would time out in 5 minutes and report a red l.e.d. "lamp" circuit failure. I bought the service manual,found 2 diodes next to one of four IGBTs to be short. D9607 (MA3X158 Switching diode) in the base emitter circuit of a driver transistor (which was also short) firing the IGBT(Q9608), and D9608 (MA3X720 Schottky barrier diode)reverse biased across the base emitter of the IGBT . Replaced all 3 with equivalents, now the unit power's up, lamp turns on for 6 seconds and then the unit shuts down. The service manual doesnt have a schematic for the Q module which has a microcontroller on board which counts hours and stuff related to ballast firing, switching lamp mode from low to high and regulation. Wish i could post a screen shot of the afflicted section here , doesnt seem possible. Any ballast experts out there to gve me some tips? The IGBT's seem ok. Checking passive components in the peripheral area too but everything checks out fine. What's the role of the schottky diode here? The circuit has 2 pairs of igbts (n channel) in series, firing the igniter transformer which lies in between the collecor emitter junctions (centre rails). The igbt pairs are driven by two ic's described as "half bridge driver master and half bridge driver slave". The heat sink on the igbt seems to be getting rather hot. This occupation gets increasingly difficult day by day . :(
- posted
18 years ago