I got hold of a “broken” Panasonic LCD projector. The lamp would start up, flicker for a couple of minutes and then shut down. No error messages where displayed.
Light! But only for about a minute or two…
The owner had send it to Panasonic to have it repaired but was told that the LPS (lamp power supply) board needed to be replaced, at a cost of €450. As that was too much compared to the price of a similar new projector the owner didn’t want to invest in a repair and decided to give up on the idea of having it repaired.
While browsing around the internet looking for clues I found some similar problems mentioned on forums, but no solution other than to replace the LPS.
I did find some LPS on Ebay for €39 + shipping, but those where second-hand which I didn’t like.
Off to dissecting the board then. When looking at the control signals going to the LPS everything looked fine. The power coming in from the power supply board was stable as well, so I figured the problem probably lay on the LPS board (as was expected).
The circuit boards inside the projector. The LPS is at the bottom left, underneath the lamp.
As the lamp flickered I figured the amount of power going to the lamp wasn’t enough, pointing towards one of the transistors generating the drive current for the lamp, some International rectifier IRG4IBC30FD “insulated gate bipolar transistor with ultrafast soft recovery diodes”.
There are four of them on the board, nicely heatsinked to a common heatsink. The first one I tested showed a short-circuit, the others were fine. When I removed the faulty one, there was no way to start the lamp.
The LPS board, with the four transistors on a common heatsink on the left side of the board.
After replacing the faulty transistor -and the others as well for good measure- the lamp started nicely, and it has been running solidly for a couple of hours now. Temperature of the individual transistors stays nicely within specifications.
Light!
At a total material cost of about €27, I consider this a win :).
Dieter Vansteenwegen (ON4DD) 
Hi, nice work. I have a similar projector (was already broken when I got it some years ago) and have had to do the transistor replacement a few times already. Should probably have changed all the transistors at once like you did, as it seems that mostly the original ones are vulnerable. I also once used IRG4PC40UD as replacement, but it was not to be long-lived, so its probably better to use the original types.
Thanks!
I figured that if one of the FETs had already died, the others must have had (at least) the same life, with the added stress on them after the first one had died.
So swapping just one seemed like waiting for the LPS to break again :)
hello sorry for bad english but i need help.
2 G4IBC30KD are changed and another 2 are OK(on multimeter), but lamp turns on but there is low light on lens and then after 15sec projector shut down. whats wrong?
thank you
Hi Jan,
If you have access to a oscilloscope, check if they work while in-circuit.
If you are not sure what to look for, compare with the two that should work fine.
If you have no access to two other FETs to change them all and no oscilloscope, I would try to take the “good” ones out and check if that changes anything.
If there is no change in behaviour, I’d replace the two that you haven’t replaced yet.
Since I don’t have the projector any more, it’s not possible to give you much more pointers on where to look exactly…
Dieter