$33 Zenith Porthole!!!

[7"estatdef]

The Zenith is on the mend. After I got it home I did the thing you are never supposed to do that is plug it in. All it would do is blow fuses. Did some investigation and found a shorted 5U4. This poses an interesting problem. Which happen first did the 5U4 die or did the filters short and take out the 5U4? So what to do? Well, I took the TV power supply and hooked up my 400v adjustable bench supply to the filter network and looked at the current the filter where drawing. It was only about 15ma so that was good enough for me. Hooked it back up to the TV and it didn't blow any fuses but no action from the set except the toobs where lit. B+ was good but no horiz osc. Did some headscratching and found a bad resistor in the plate circuit of the osc. Replaced that and now things are happening! But not things I want to happen. The plates of horiz output toobs are cherrying (glowing red) which means no bias or drive. Time for a cup of coffee. Poked around a bit and found a shorted coupling cap from the osc to the output. Replace that. Now things are looking good! Horiz osc and output are working I've got HV on the picture tube got boost so seems like I should have a raster but I don't. Hmmmmmmmm scratch scratch. All the voltages look good on the CRT so this has me stumped. Just for the heck of it I took a jumper wire and jumper the CRT cathode to ground. And bang I had a raster! What had happen was the video output coupling cap was shorted which in turn put 120+ on the CRT cathode turning the face black. Replaced that cap and the set not only has a raster but has a picture from a local station. Actually two pictures from the same station. The sweep sections are going to use some going over.

I'm getting an order for the caps together for this set. Normally I would not just plug it in and let'er rip nor would I advise anyone else to do the same. If you do can do a lot of damage by doing this.
Terry

"Things look better in black and white"
Simon&Garfunkel 1982