RCA F31317 lost blue in picture.

RCA mod# F31317 (svc# F31317-YX53), Chassis# CTC203CA6

This is another try for any other possible checks or solutions. One prior submitted solution to check several resistors on the CRT board failed to find any problem. I am still open for any suggestions. Is it just a boat anchor or a repairable unit (within reasonable costs)? Does anyone have a schematic?

Unit is approx 6 years old (per prod. date). Lost blue in picture. Picture has a sepia-like appearance. Reds are still good and green is there also. No noises occurred and there was no indication of a failure prior to the loss of blue in picture. Found service mode label inside case. Checked the blue control parameters. No adjustment can be made to the blue switches that have any effect on picture color quality. The red and green can be adjusted. The first 3 parameters are codes and each one shows code 24. I cannot find any info to define these codes. Checked the circuit board attached to the rear of the tube for cracked solder joints. No cracks visible but I touched a solder iron to each to attempt a possible fix to no effect. Checked all plug-in connections for tightness and cleanliness, NPF. I have not removed the main board to check for solder joint integrity. There are no visible damages or failures on the main board.