I found the AGC (labeled "DX Range Finder") and it has no effect as far as brightness is concerned. I checked all the resistors in close proximity (circuit-wise) to the picture tube and all seem to be in spec, and all the voltages are reasonable
I managed to hook up the CRT tester via nails and jumper cables using the information Rich12 provided (thankyou) and although no shorts were present, it seems the picture tube is completely dead: no emission or gun balance (cutoff) whatsoever. I checked and double checked my connections and they all appeared to be correct. what seems weird is that there is NO needle response at all for emission (and a slight drift from extreme to extreme of the knob for cutoff), but a raster/picture IS visible - a VERY dim one, but one none the less.
Also, the tube doesn't appear to have seen very many hours. the gun hasn't turned blue/violet from heat the way shango066 points out in some of his videos, And one would reasonably expect the previous owner would have retired the set LONG before emissions got this bad on its own. (Although, I guess I should mention that I'm only 21, and I've never actually seen a TV running with a weak picture tube - and know that that's the problem; I have nothing to refer to)
I did try the rejuve1 function, but nothing happened. I'm hesitant to try rejuve2 until I know for sure I have access to a replacement tube, or find the correct adapter socket for the tester just on the off chance I didn't jumper it correctly (I at least know I hooked the filament leads correctly)
I also tested the tester on another known-to-be-good color crt from an old computer monitor and everything appears to work, so I have ruled out the tester itself being faulty. I chose to purchase this particular tester after watching this video:
https://www.youtube.com/watch?v=pOXJLlho2eI
The original tube in that video had the EXACT SAME symptoms my crt is having and I was hoping mine had a removable G1 short as well.
I guess this means I'm now truly in the market for a new 21ZP4
maybe if nothing else I'll try and see if Kamakiri still has his and if he'd be willing to freight it to me....from NY to all the way to TN...
