My rca kcs 136 does have a nice raster with snow and great sound BUT, when i connect any source to it, nothing happens. I replaced a bad 6cw4 rf amp to no difference. Thoughts?

If no sound either (assuming intercarrier sound), then you want to look at the video detector, video IF and back through the tuner.

Do you have a B&K 1075/76/77 analyst? One of those will allow you to inject video, IF and RF to find your dead stage.

Another thing that is possible, but unlikely with the snow, is bad AGC bias.

If you have good clean strong snow the tuner is the cause
99% of the time.
Another easy test is turn the channels. You should see crashing in the
pix & noise from audio from the switches moving.
Try the mix/osc tube 1st even if it tests good.
Check the B+ to the tuner.
Check the AGC. Can be subbed to test if way off. AGC is RARE problem.
Usually a dead RF amp will still let a strong signal pass but snowy.

Last thing is a VERY dirty tuner. Try a good shake of the knob & see
if the channel pops in.
DO NOT spray clean an RCA Nuvistor tuner ! It can throw off the RF amp
& cause it to oscilate. Take time to pull the tuner down, remove
usually 2 shields & just put cleaner on the contacts, spin, & let dry.

73 Zeno:smoke:
LFOD !