Quote:
Originally Posted by old_tv_nut
"Video appears to change every 16 seconds"
This is an indication of AC line rate hum somewhere. 16 seconds is the beat period between AC power and NTSC 59.94 Hz field rate. It will show up with a full-standard NTSC source, but not with old test gear that locked the vertical to the AC line.
Bad power supply filtering? Maybe a heater-cathode short?
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I am in process of changing the electrolytics a few at a time, though none are heating up, they may be past reforming again. Im using the VA-48 for video, possibly explaining that periodic differentiation-style spikes going to the 6KA8 grid. It cannot even show a good air signal via the ch 6 broadcast MOD I'm using.
The H-K short must be somewhere possibly back-feeding video, from output 12BY7? I also need to throw my iso-trans/non-brightener on the CRT, it (had) tested good except with a H-K short in blue gun
Gray scale is easy to set, but with an H-K short (considering B+ is on heater winding) THAT would present an obvious clue!