Panasonic PT-L735E ballast blues :(
 

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 . :(

"jango2" wrote in message
oups.com...
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 . :(


Well you're making progress, in my experience with electronics in general
there's a good chance whatever problem is left is something small, simple,
and rather obscure.

Panasonic has a rebuild kit for the ballast assemblies, if that fails then
you can call Panasonic for authorization for a new ballast assembly.
"James Sweet" wrote in message
news:uSNue.4622$fw1.2605@trnddc02...

"jango2" wrote in message
oups.com...
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 . :(


Well you're making progress, in my experience with electronics in general
there's a good chance whatever problem is left is something small, simple,
and rather obscure.