'51 Magnavox vertical osc transformer

[DavGoodlin]

Update:
Replaced the vertical blocking oscillator transformer and got a dim but full raster. Sound transformer required a tweak and tuner cleaning brought in a nice picture on a very weak 17BP4. The RF-IF-Video and Sync were functioning perfectly using a DT converter box as RF source. Aggressive CRT rejuvenation still yielded near zero emission, evidenced by the poor cutoff (silvery infill of bright areas) as brightness is increased. Cranking up filament to 12 volts did very little to help, so cathode must have been stripped. I decided to part out a 1954 Motorola table model with a strong testing 17KP4.

Lowering the B+, which ran at 445v, 45v higher than the schematic stated. I had some NOS 500 volt 40 mf, so I used these on both the 380 and 400 volts supply. As I lowered line voltage with "Powerstat" variac from 122 to 117, it dropped to 405 volts with no effect to operation whatsoever. I tried the two 1N1007 in place of rectifier tube 5U4 and a series resistor to compensate for voltage drop of 5U4, (44 volts @ 225ma). A 200 ohm 10 watt resistor dropping 40 volts at 200ma got too hot and as line was increased from 115 to 120, B+ topped 430 volts, with 475 at the rectifier diodes junction. Not a solution where line voltage varies, even just 3-4 volts. There is only one solution left, make a buck or boost auto-transformer using a filament transformer. I this case, I found a 120v-5v@3A Stancor. This was a better solution than a pair of 2.7ohm 10 watt wirewounds in series with the 120 volt AC supply. The TV draws 1.7 amps, well within the secondary rating of the transformer. Power in at 120 volts, TV gets 115 volts to power transformer and B+ stays below 410v, only peaking at 480v before set warms up.

Current Issue: The replacement CRT looks good and bright but has electrostatic focus, so I removed the permanent magnet used for focusing the 17BP4. After connecting the CRT focus pin 6 to boost 520v, B+ 380v and ground, there is no difference. The center of the picture is out of focus but edges seem sharper? Adjusting the ION trap seems to make it clearer in center but not at the same position for max brightness, huh

Question: The CRT has an unused warranty tag listing it as "17H/KP4". 17H has pin 6 for electrostatic focus and 17K lists internally connected focus anode, yet pin 6 is there. Should I reinstall the focus magnet and leave pin 6 alone?