If one of the damping resistors or caps was to change value or short on the yoke it could affect picture linearity or kill horizontal sweep all together.The 7jp4 in my vt-71 which tests good can be seen clearly in room during the daytime.The HV on my set is around 6.5 kv.The only way you could figure out how bright a new 7jp1 would be to find a NOS 7jp1 and compare it to a used one.