interesting tough dog on CTC-15/16

[DaveWM]

I was reading up on a RCA color service manual about width problems on RCA roundies. the problem presents as low cathode current on the HOT, and too much neg on the control grid. Seems the engineers designed in a safety brake on the HOT to keep the HV down in case of a shunt tube failure involving tapping into a source of neg voltage that would cut off the HOT tube. the source is from the grid of the Blanker tube that is on the chroma board, nearest the HOT. There is a 390k ohm resistor that goes from the grid to ground thru a narrow trace along the side of the board. The Heat from the HOT causes a break in this trace. Other problems include some loss of brightness but it does not show up like the loss of width. A check of the horz blanker grid will tell if there is problem as it will be too neg when compared to the sams listing.

It was recommended that the trace be bridged over anytime the set is serviced.

I imagine this applies to clones as well.

per the manual there are three sources of bias to the HOT, the rectification of the osc drive (neg) the blanker tube grid (neg) and a 10meg resistor to the b+ (positive). So if the PP and wave form from the osc tub look correct at the grid of the HOT, but the total bias voltage is not, then suspect one of those other bias sources.