Ok. Let’s try this again…RCA 9TC240 Alignment

[Chris K]

Thanks for your thoughts on this Tom. I don’t know enough about my isolation transformer to say anything about its ground protections but all of the VTVMs I’ve used have had nonpolarized 2 prong plugs. They’ve all been from the 1950s.

[Electronic M]

Originally Posted by Chris K

Thanks for your thoughts on this Tom. I don’t know enough about my isolation transformer to say anything about its ground protections but all of the VTVMs I’ve used have had nonpolarized 2 prong plugs. They’ve all been from the 1950s.

When you've had an old isolation transformer developed a primary to secondary short (which also acted as a step up winding) that you accidentally found with your bodys internal volt meter or a persistent ground loop in an agile modulator or ever got zapped connecting a 50s stereo component to a 80s stereo component with a grounded cord you start to learn to check exactly how much your gear is grounded or isolated as well as whether it's hot from line to chassis "safety"/RF line filters despite having a power transformer... Mistakes can be powerful lessons/impetus to learn and check things.

It is important to check grounding between any devices you interconnect even if they're designed to be internally isolated as that can fail. I often measure voltage between devices with my battery powered DMM to prevent sparks flying on interconnection.

BTW metal cone CRTs aren't terrible to handle if you work smart. Always discharge the HV with a HV meter (to prevent dielectric bounce back in the caps) and get a glass test CRT (most metal cone sets a all glass 5AXP4 is the right one) so you can make it run well with the test tube, then at the end reinstall the metal and do width, height, linearity, centering and focus touchups.