7JP4 restore ?

[JohnCT]

Originally Posted by Notimetolooz

There were TV CRT brighteners that contained an isolation transformer on the filament for tubes that had a H-K short. You might be able to find one and adapt the sockets. However, you would still have the emission problem, unless the emission test was being thrown off by the short.

In the 1990s, H-K shorts were common with Zenith picture tubes. Since these filaments are sourced from a secondary flyback winding, a special toroid isolator could be bought and installed.

What I used to do is place 2.5 turns of regular insulated wire around the flyback core, then run the wires to the CRT socket and attache them after cutting the traces on the CRT board in order to isolate the filament pins from ground. I then slid the winding up or down the core to get the filament as close to (low side) of 6.3VAC using a TRMS meter. I sometimes added a 5W resistor to the arrangement if needed to keep it at 6.3 or just below.

The same could be done with these old tubes if an isolation brightner can't be found cheaply with the same socket arrangement.

John