I was thinking too low of a frequency. Probably high or low can cause problems. I searched and found this: https://retrocomputing.stackexchange.com/questions/66

I was thinking too low of a frequency. Probably high or low can cause problems. I searched and found this: https://retrocomputing.stackexchange.com/questions/6614/can-the-wrong-sync-frequency-really-destroy-a-crt-monitor https://retrocomputing.stackexchange.com/questions/6614/can-... "At the too low horizontal frequency, the period the switch is open becomes too long, that causes the following" [various bad things explained]