Hi.
If you have the Hitachi rear projection TV, then there are different defects that will result in sound but no picture. The purple light is not an error code.
First check if problem is affecting the signal from external DVD or any other external source. If the problem is only on one source, then the fault is a connection cable. If it happens only with the internal DVD, then the problem is the internal connection cable
More commonly you will get sound but no picture with all sources. In that case the first part to be tested is the board that supplies power to the lamp (someone calls it ballast). If the board is OK and powering the lamp, then the lamp must be replaced even if lamp light is not on. The ballast is an high voltage board-it must be tested by a technician.
If ballast does not get power, then the PSU must be tested. The PSU supplies power in different voltages. The DC line to lamp is not coming up. If PSU is OK and lamp ballast is OK, then problem is light engine or main controller.
Here all parts:
Hitachi 46W500 Parts ListHere a service manual. A few dollars fee is required for download:
Hitachi - 46W500 Service ManualRegards.
Ginko.