The machine takes CL484 as the decompression chip, KDA04084 is the video DAC, KA2198BD is the standard encoder.3Q7service manual download site
Acoustic image inherent, indicating that the extract of some of the basic normal; red screen display, the fault has three possible: first, poor CL484, only output 8-bit red data or blue, green data in transmission loss and did not enter the video DAC; second, DA converter bad, only red color signal output or blue and green color signal lost; third, poor standard encoder and can not output R, G, B three mixed composite video signal. Check 484 and 04084 and 2198 peripheral are disconnected, weld, with an oscilloscope direct observation video encoder 2198 tricolor signal input end and has the signal input, indicating that the normal CL484 and the video DAC. Determine the standard encoder 2198 damage, change, the fault is still! So far, maintenance into trouble. Careful analysis, since the three primary color signals were, standard encoder and normal, then the problem must be in the periphery of the DAC or codec. Then disconnect 04084 and encoder 2198 connected trichromatic coupling capacitors and found that when disconnected from Cr and screen display red immediately disappear; only blue and green mixed color; before disconnecting the CG, the screen will display the remaining blue image; but connected to the Cr, displayed on the screen immediately to red. Doubt CR problem, welding measurements, there are about 10 of the leakage resistance, replacement CR, troubleshooting. In this case the cause of the malfunction CR serious leakage, lead to enter the encoder red color signal amplitude is too large to mask no blue and green signal.3Q7service manual download site