The DMHD04D has 3 LEDs showing the status. On the front panel the power LED will be red during boot up and turns green once boot is complete.
On the rear of the unit, there are 2 LEDs; 1 near the HDMI connections is the encoder indicator and this should be flashing a combination of red & green in normal use. The LED near the RF connections indicates the status of the modulator. this should also be flashing a combination of green & red.
If any of the LEDs are solid red then a fault has occurred and you should contact your supplier to seek a repair or replacement.
The DMHD04C status LEDs are outlined in the image below:
