Advice needed- Zenith Z 4517-06. My first tube color set - Videokarma.org TV - Video

fsjonsey · #1 07-07-2007, 01:19 AM

Well, i found my first tube color set today. Its a zenith all tube color set with a rectagular CRT in a Colonial cabinet. The cabinet is a little worse for wear, it was dropped on its corner and the paper thin plywood cracked. The set works, but the picture has horizontal retrace lines that I cant seem to get rid of, and the flyback makes noise that reminds me of static, but is not arcing. This does not effect the picture.. The picture tube tests good on all three guns on my b&k 465. What are some possible causes of the retrace lines?

jpdylon · #2 07-07-2007, 01:54 AM

The retrace lines can be caused by excessive screen voltage. Flip the set into service mode and see if you have a bright white line. if so, quickly turn down the screens until its all black.

Turn up the red until you see a faint red line, then turn up blue until you see magenta, then turn up green until you see a gray line. flip the switch back to normal, adjust brightness and see if your retrace remains. Also clean the service switch. Sometimes oxidized contacts will cause strange symptoms your having.

As far as the noise you hear, sounds like corona discharge. Open up the high voltage cage and clean out all the dust you can. A faulty high voltage rectifier heater winding can also cause this symptom. Turn the set on in a darkened room with the HV cage open and see if you can see a blue haze --indicating the corona discharge. Also clean all surfaces around high voltage components. This includes the HV cage, horzontal output tube, damper tube, HV regulator (this set may not have one) and rectifier tube, as well as the bell of the picture tube.

Good luck with your sets. Zenith color sets are some of the finest.

BTW, where are the pics?

fsjonsey · #3 07-07-2007, 02:39 AM

I was also wondering if anything can be done about the yellowing around the edges of the picture tube behind the safety glass. they aren't horrible, but annoying to look at

fsjonsey · #4 07-07-2007, 10:11 AM

Well, i turned it on this morning and was greeted to a loud snapping noise. I looked behind the set, the flyback was arcing. I quickly cut the power and let it be. Is the flyback shot now, or is there anything i can do to clean and recoat it?

jpdylon · #5 07-07-2007, 11:15 AM

The yellowing around the edge of the picture tube is known as the "Green Halo" its basically the other less extreme equivalent of a cataract. It is much harder to remove than a cataract and you have a greater chance of breaking the safety glass. I would leave it as is unless its really bad.

If the flyback is arcing over, its toast. There is a short in a winding somewhere ans it needs to be replaced. Someone here may have the number, or you can get your hands on a sams for the set and see what the part number is. Moyers electronics will probably have one.

fsjonsey · #6 07-07-2007, 09:08 PM

Good news!
Its not the flyback that's arcing, but the HV rectifier socket! Will scrubbing the entire socket with alcohol remove the carbon traces, or will i have to find a new socket?

jpdylon · #7 07-07-2007, 09:43 PM

You can try using de-oxit with a pipe cleaner, but more than likely you will need to replace the rectifier socket. Also test the HV rectifier to make sure it hasn't been injured or is the cause of the arcing. Check the pins on the rectifier for scorching or green corrosion.

What HV rectifier do you have? If it uses a 3A3 I may have a spare for you.

fsjonsey · #8 07-08-2007, 09:20 AM

I pulled the socket out of the HV cage to have a look. The rubber coating that zenith painted over the socket pins and anode lead solder joint is dried up and falling apart. Should I clean it and recoat it with RTV silicone? What brand of RTV silicone do you recommend?

andy · #9 07-08-2007, 10:27 AM

Where is it arcing to? The HV rectifier socket should be completely containd within a plastic cup to prevent arcing. If it's arcing through a crack, or hole in the cup, this should be repaired, or replaced. It's not a bad idea to insulate things with silicone, but in this case, it shouldn't be the only thing to prevent arcing. You can get special silicone designed for HV insulation, but I've never had any trouble with GE silicone II.

fsjonsey · #10 07-08-2007, 11:32 AM

The black silicone compund that zenith put on the solder lugs of the tube socket has dried up and fallen off. The arcing was taking place between the lugs.

andy · #11 07-08-2007, 12:19 PM

That's odd. There shouldn't be any significant voltage between the lugs (just 2v for the heater).

fsjonsey · #12 07-08-2007, 07:18 PM

Is it possible to substitute a 3db3 for a 3dc3? Its the only other similar rectifier i have.

fsjonsey · #13 07-08-2007, 07:43 PM

I tried using silicone, but it doesnt seem to be doing any good, the arc burns right through it. The cabinet label said that either rectifier should work, so i subbed in the 3db3, with the same results. Does anyone here happen to have a good rectifier socket they would be willing to part with, for a price, of course. Or, should i try something like corona dope first? The plastic cup is in perfect condition, with no cracks or holes, but the socket itself is arcing from pin to pin.

andy · #14 07-08-2007, 07:53 PM

Are there any resistors on the socket? Check to make sure they aren't open. There should be nothing to arc to from pin to pin. All the pins of the socket are at the same vlotage.

fsjonsey · #15 07-08-2007, 09:06 PM

Quote:

Originally Posted by andy

Are there any resistors on the socket? Check to make sure they aren't open. There should be nothing to arc to from pin to pin. All the pins of the socket are at the same vlotage.

There are no resistors on the socket, only the two wires from the flyback and the anode lead, which is soldered to the same pin as one of the two flyback leads.