Another Project?

[bandersen]

Sweet Maybe you can try this modification to eliminate those retrace lines ?

[leadlike]

Yesterday I got a great deal done, along with the usual amount of heartbreak and compromise. But as the day ended, I had a working set in my living room.

First, the bad news: I pulled the crt to clean it, and saw that it has hairline cracks all along the neck. This tube is a rebuild, and there are two large cracks running along the length of the rebuilt portion of the neck. Whether this is a failure of the rebuilder, or as a result of it being moved roughly (though I packed the tube in a fitted box every time it was remove from the chassis) it is tough to say. As it is, the tube is holding its vacuum, and produces and excellent picture, so it will work for awhile. I imagine it will continue to function until the cracks grow around the crt neck, and the whole thing pops apart.

Luckily, I have a 10" Admiral that I am converting to a 12" set, so I had a spare crt. I will use the cracked 10" for a tester until it completely comes apart. The screen isn't aluminized, but it still produces a brilliant picture. I added A/V jacks to the chassis, adding audio at the selector switch (so the radio/phono audio isn't overidden by the tv audio) and video directly into the grid of the video output tube.

I also dialed in the B+ on an adjustable wirewound power resistor. Because I used a dropping resistor to burn off the excess voltages produced by my replacement transformers, this creates an issue when switching from Tv to radio/phono. When switching from tv to any other function, most of the set's tubes are shut off, altering the output current of the transformers, and effectively raising the B+ by about twenty five volts. My compromise was dropping the B+ by about twenty volts when the tv is powered up, so when one switches to radio, the voltage will only climb to about five volts over the rated B+. Filament voltage is not affected by this, only the plate voltage, so I shouldn't have to worry about cathode poisoning or any of that good stuff.

The final modification was adding the vertical blanking circuit.Following the ETF link Banderson provided, I reduced the retrace lines a great deal. It was fun to watch those waveforms on the scope.

I now have the set in the living room on top of our CTC-9. It is hooked up to a temporary speaker and dvd player. I plan to play this thing for as many hours as I can this week to shake out any other issues. It played for about four solid hours last night, and I never once had to adjust anything. These are solid sets, and probably would have rivaled the 630 chassis if GE hadn't designed it to be anything other than a 10" set (IE, no provision for space on the chassis beyond the stock crt, making the radio integral to the chassis, etc.).

[bandersen]

Nice job Glad the ETF mode worked. Too bad about the CRT though - mine's just about dead too.

I was wondering about that mode switch and the TV tubes. I suppose they're cutting off the juice to the filaments ? Must be a hefty switch if they are.

I can't wait to get started on mine

[leadlike]

....and here it is, playing away. The gentleman in the picture is actually somewhat relevant to this forum, so keep an eye out for him in another posting.

GEDC0184.jpg

[bandersen]

LOL - it looks so much smaller outside of the cabinet. Nice picture too - both the TV and photograph that is.

[leadlike]

Thanks. A couple of points for the 802 you have that I keep forgetting to tell you about:

That chassis flexes pretty bad, as I mentioned before. But I'm thinking maybe that's what cracked the crt neck- it got pinched and the neck wound up supporting the full weight of that chassis when it was being carried around.

Also, it looks alot like your 802 was run as a radio/phono only for some time. The tubes that I can identify are the ones that were only necessary to run those functions. Since your crt is pretty dead, that is likely the cause of why the tv may have been taken out of service, but proceed with a bit of caution, because something else major may be dead in that tv.

As for the chassis looking so small in that picture-well, the CTC-9 has the footprint of a full sized fridge. Those early color sets are huge!

[bandersen]

Thanks for the advice. I think you're right - the previous owner did say that they used it as a radio for a long time. I'm a little concerned about the replacement flyback, but we'll see.

[leadlike]

The dead crt tells me that is likely why it was retired. Maybe the tv shop that wrote "return chassis" on it bought those sweep tubes. I can't see any reason why the owners would have pulled them.

I'd guess that by the time the crt gave out they had a larger screened set by then and just left it as the radio phono.

[bandersen]

I bet you're right!
Do you have any pics of your focus knob ?