Originally Posted by klau58
I'm having some issues with my Mitsubishi WD-62825 DLP TV. When I initially power the TV on, the green light blinks for a minute (normal) but the lamp never powers on. The trouble code given is 3-4 which equals "lamp abnormality". I first decided to change the lamp, even though my old lamp did not appear to have anything wrong with it, but that did not work. After doing some research, I concluded that it must be either the Power PWB board or the lamp ballast board. I then checked all of the capacitors on both the main power board and the ballast board. None of the caps appeared to be blown (none popped, none had a dome shape, none had discoloration). Like a fool, I then assumed it MUST be the ballast board, so without doing any diagnosing, I ordered and installed a new one. Same problem. WTF. I then decided to check the input power going to the ballast board and got a value of 313VDC (research tells me it should be 330VDC). My questions are the following:
1. Is 313VDC within the acceptable tolerance range of the input power to the ballast board?
2. If not, and the problem is not capacitors on the main power board, any idea what else could it be?
3. What should the output power from the ballast board to the lamp be (maybe the new ballast board is bad)?
4. If none of the above, any suggestions?
In the interest of full disclosure, I should also note this issue arose the morning after I hooked up an XBOX Kinect for the first time and played some games. Could the jumping around and vibrations have caused any soldered joints to break loose?? My family and I played some games and watched TV for about an hour afterwards and nothing seemed wrong so I would be very hard pressed to believed that, but I've seen/heard of stranger things.
Thanks in advance.
1. Probably. I'm not going to look up that Service Manual right now, but most ballast input voltages have a fairly wide tolerance.
Re troubleshooting ballasts; all tvs that have a ballast/UHP lamp combination have a similar start sequence. At some stage in the overall bootup sequence, a signal is sent to the ballast to fire the lamp which requires a voltage of a few KV to initiate the arc. Following that the ballast switches over to a sustain-arc-voltage of a few hundred volts. If the ballast/lamp can't sustain the arc, the sequence fails and a timer starts. The timeout is roughly 20 seconds. After that, the ballast will make another attempt, timeout twenty seconds, try again, and if it fails a third time, declare a failure indication of some kind.
When the ballast tries to fire the lamp with a few KV, you can hear and see it happen. On all ballasts, beside the HV wires that lead to the lamp, there is a white ceramic element that looks like a fat resistor. It's called a spark-gap device. When the ballast generates the few-KV arc initiate voltage, you can hear a buzz or sizzle, and if you look at the spark gap device (in the dark) you will see it glow. If you see that, and note the three-times twenty second sequence, it is likely that the problem is downstream of the ballast.
Knockoff Chinese UHP lamps are getting very common. They sell well because they are cheap, $30-40. They are also unreliable; they often don't work out of the box, and when they work they don't last very long, like three weeks to six months. When they work they can be scary bright. You can't tell if a lamp is good by looking at it, or testing it with a meter. It's an arc-lamp, -there is no filament, just a gap inside the glass tube.
Don't discount that which lies between the ballast and the lamp. The connectors at the housing take a lot of heat and can crumble with age. I've seen lamp housings and lamp connectors that look fine but when the lamp is inserted it just pushes the inside connector out of the way. Lamp fans can also become so plugged up with dust that the lamp will overheat very quickly. There will also be a thermal sensor in the area of the lamp that can shut down the tv if the temperatures get too high, or it can fail itself.
If you don't have a Service Manual, you should track one down.