Panasonic PT-40LC12 and PT-45LC12 Tips

Ballast Repair Kit for Panasonic PT-40LC12 and PT-45LC12

This thread is basically a continuation of http://www.avsforum.com/avs-vb/showthread.php?t=958640

Based on brogers' thread, I ordered the same ballast repair kit intented for the Panasonic PT-xxLC13 series and applied it to the Panasonic PT-xxLC12 series.

Please note that the following information is provided at your own risk. What worked for me may not work for you. This procedure involves soldering and electronic experience!

Apparently, after many ballast and bulb failures, Panasonic put out a kit of components marketed as the "Panasonic Ballast Repair Kit", #LSUC0022. This kit contains 1 transistor, 1 resistor, 2 diodes, 1 capacitor, and 1 fuse. The purpose of this kit was to replace probable defective components on the Ballast circuit board.

There are two versions of this repair kit. The older version, LSQL1865, contains the original parts supplied to the PT-xxLC13 family. The newer version, LSQL1865-1, contains newer equivalent parts that were supplied to the newer PT-xxLC14 and later families of Panasonic TVs. If you have a choice, I would get the newer version, as there may have been improvements to the componenents.

I received the older version (not by choice), whereas brogers received the newer version.



The kit matchups are listed here, and where each component gets installed:

The PT-40LC12 combines the LCD power supply (1700 series) with the ballast (1300 series) on the same circuit board. Therefore, the component locations are different on the PT-40LC12 than what is mentioned in the kit for the PT-50LC13.

Also note that this kit contains only one transistor, whereas the PT-40LC12 and PT-50LC13 has at least 4 transistors. It might be worthwhile to order additional transistors and replace them as a set.

Also to be noted, the ballast on the PT-40LC12 is buried underneath the bulb housing, unlike the PT-50LC13 which is located right at the rear of the set. Therefore, the PT-40LC12 needs major unassembly to get to the ballast.

Here are the steps needed to get to the ballast:

1) Unplug the TV you are going to work on.
2) Remove the TV rear cover by removing 20 screws.
3) Remove the AV flip-down front door.
4) Remove the front left and right speaker covers.
5) Remove the front center panel by removing 4 screws, and unplugging connector P6303.



6) Remove the lamp cover door.
7) Remove the lamp housing (that contains the bulb).
8) Open the front base panel by removing 16 screws. Remove the ground strap screw so that the base front panel can lay down.



9) Unplug connectors P1010 and P4504 from the main circuit board.



10) Remove 4 screws that attach grounding straps and grounding plates to the ballast.



11) At the rear of the set, remove the duct fan by removing 4 screws. Unplug connector P804 from the main circuit board.



12) Remove the Audio Power unit by unplugging connector P1101 and removing 2 mounting screws.



13) Remove the 10 screws as shown. Basically, you are removing 2 screws to release the lamp socket on the lamp housing. Then remove 2 screws to the temperature fuse on the lamp housing. Remove 1 screw to the ground plate and ground wire on the lamp housing. Remove 1 screw to the ground wire on the ballast. Remove 2 screws that hold the ground plate to the ballast. Unplug connector P1905 from the LCD Main circuit board. Finally, remove 2 mounting screws that hold the ballast cage to the base, and lift the ballast cage out of the set. See diagram.



14) Pry off the cover to the ballast cage. Unplug connector P1703 and fully remove the cover.



15) Remove the ballast circuit board from the cage by removing the 3 mounting screws and lifting the circuit board from the posts.

16) Locate each component as shown. Each component name is clearly written on the circuit board. Replace the components with the new componenents from the kit. Note polarity especially with the diodes. This procedure involves soldering and electronic experience!





17) Reassemble everything in reverse order. Take your time, and pay attention to reconnecting all the connectors and grounding plates, straps and wires.

If you notice anything missing or inaccurate with these instructions, please let me know. Sorry for the watermark on the pictures; they are to help prevent the sale or misuse of these instructions. Thanks to brogers for initiating this process!

It probably just blew from age and usage. However, if the new one you install blows, then it might need more investigation.


I believe the repair kit was offered to solve the "bulb not lighting" problem. Whether it protects or extends the life of the bulb is not really known.

As far as the capacitor, according to the Panasonic parts list the replacement capacitor in the kit is the same value, but probably bigger and beefier.

If your set works normally after the thermal fuse replacement, it would probably not be worth the risk of installing the ballast kit.

Reference here.

The service manual indicates that the code means the air filter needs cleaning, or replacement.

You seem to be experiencing the same problem as this post.

His solution was to unplug and replug the connector to the lamp thermistor (the small circuit board mounted above the lamp cage).

The purpose of the lamp thermistor is to detect overheating of the bulb. If the thermistor is bad, it can be replaced ($4 part #D4CE31330001).

The part you originally replaced was the temperature fuse, which is different from the thermistor.

Paul -

You have two errors going. I am going to give you what is mentioned in the service manual.

Temp LED flashes once every 5 seconds

Cause: detects open or short of the Temperature Sensor (R2911) on Front Thermistor C.B.A.

Resolution: Replace the Temperature Sensor (R2911) on Front Thermistor C.B.A. If still No Good, replace the Projection Unit. Note: The Projection Unit includes LCD Main C.B.A.

Temp LED flashes 4 times every 5 seconds

Cause: detects the temperature attached near the Lamp by the Temperature Sensor (R2901) on Lamp Thermistor C.B.A., then indicates the error when the temperature becomes more than 60 C (140 F).

Possible causes:

1. Clogged air filter.
2. Blocked air intake.
3. The surrounding temperature of the place of use may be too high.

Resolution: Cleaning the Air Filter.


The above is what is mentioned in the service manual.

The least expensive repair is the check or replace the front fan thermistor, ~$3.50, #D4CA35030002. The projection unit is very expensive.

You might also want to check the filter and the way it seals, to insure no blockage. Also, check both the front fan and lamp fan, and be sure both are spinning at a reasonable rate.

Hope this helps!

Jwburt -

Never had your problem.

But you seem to have figured out most of the possibilities.

It is probably your lamp that is causing the problem. For some reason your TV circuitry is detecting abnormal voltages with your bulb; it's probably drawing too much current to keep lit. If it was temperature related, the temp light usually flashes instead.

I don't think the temperature fuse or the thermistors are causing your problem, but they are inexpensive to replace.

That leaves pretty much the lamp or the power supply (ballast).

You could try reseating the connections between the thermistors, lamp, power board, and the main board. Maybe a high-resistant contact is causing the problem.

Not sure if the ballast repair kit would help your problem. Usually the kit is used to solve a non-starting lamp, although other benefits are not known at this time.

The true Panasonic lamps appear to solve most problems. The other "OEM" lamps seem to be a crap-shoot ... maybe they work, maybe they don't. And, those "OEM" lamps seem to have a very short lifespan if they do work initially.

Please let us know how you solve this. Thanks!

Usually it is either the bulb or the ballast.

There is a chart of the blinking lights here.

Found a copy of the Panasonic PT-40LC12 and PT-45LC12 Service Manual here.