Zenith H2447R 19" Porthole TV

[Sandy G]

You fellers who really know how to Work on this stuff are near Deities in my book.. I tried to learn enuf to maybe change out caps & resistors & stuff, but even THAT was beyond my 57 IQ abilities...

[Crist Rigott]

Let's try and get caught up a little at least from the start.

After removing the chassis from the cabinet, I took many of the customary initial pictures of both the main and power supply chassis. I removed the tubes earlier when transporting the TV back home. I then removed the CRT.





I then decided that this thing needs a bath. I went to the local "Quarter" car wash. Yup the local car wash. I used the "Presoak" setting to spray off both chassis on top and on the bottom. Then I used the "Ionised Water" to rinse them off. These settings at the car wash use a lot less pressure and with the wand 3 feet away, the car washing did an amazing good job of cleaning those chassis. Once back home I blew off the excess water with my blow gun set at 40 pounds. Then the chassis went into the oven set at 170 degrees F for several hours. Well worth the effort.

[Crist Rigott]

I then wanted to check the "health" of the chassis by checking all the transformers and coils. All checked good even the nasty looking flyback except the H Hold coil L22 (Sams).

I removed the coil.


I then unwrapped the black tape. Sure enough there was a broken wire.




I was an easy repair to make. I unwound 1 turn and cleaned off the insulation and soldered it back on to the green terminal. If you look closely you can see the original wire underneath the white tape.


I then used some black electrical tape to secure the wire.

[Crist Rigott]

Then I labeled each component according to Sams 120-13. This is my usual practice. This helps me understand the chassis and the parts locations. When labeling the parts I checked their value against the parts lists. This readily points out what the differences are. Sure enough there were just a few. The Sams had a few typo errors and I also used Riders V6-1 to cross check both the Sams and Riders and the chassis. The biggest difference was R39 (located under L14) is listed as a 33K resistor wired to the 130V bus. This was what the picture shows to be in the Sams. But the chassis has a 75K resistor wired to the 360V bus. The Riders shows a 68K wired to the 360V bus. I'm thinking that perhaps a 68K 1W resistor was in short supply and a 75K was used on the assembly line. Most likely I'll use a 68K resistor.

Also you'll see that I removed several shafts from the front of the chassis to a pot and the tuner to have better access to the components. These will be cleaned before reinstallation.

[Crist Rigott]

I removed the HV cage and disconnected the 4 wires going to the flyback.







After removing the 1B3GT plate wire along with the 6BQ6GT plate wires and the door knob cap and 1B3GT socket I ohmed out the coils. They checked good. I then cleaned up the coils by removing the melted covering by chipping it off and using heat to melt it some. I used a lot of Q-Tips and acetone. I then cleaned off the yellowed cad plating and cleaned up the rest of the assembly.





After cleaning I then baked the assembly at 225 degrees F for several hours. I then used my MG chemical Super Corona Dope and brushed on 4 coats. 1 coat on one side then bake for an hour, the do the other side and bake it again for an hour. This was repeated for 4 coats. The coils are just about filled and 2 or 3 more coats I'll be done. Stay tuned for the results.

[Electronic M]

With how toxic cad plating is (and that it is original) I usually try to leave it alone.

Given the set has not ran in a long time I'd be leery of completely sealing the fly windings. Sometimes moisture collects in the windings and it takes a while running the set for it to boil out....Plugging it's escape route seems like something to avoid doing.

[Crist Rigott]

Originally Posted by Electronic M

With how toxic cad plating is (and that it is original) I usually try to leave it alone.

Given the set has not ran in a long time I'd be leery of completely sealing the fly windings. Sometimes moisture collects in the windings and it takes a while running the set for it to boil out....Plugging it's escape route seems like something to avoid doing.

The CAD plating is removed easily and is captured in the solution. I think it's best to get rid of it once and for all.

Remember that I baked it prior to sealing.

[Kevin Kuehn]

Looking good! At some point I need to try dipping a flyback in Polyurethane varnish and see how it holds up. The Super Corona Dope MSD sheet says it's a modified Alkyd, which I'm assuming means it's a your basic Alkyd resin with Polyurethane additive for better flexibility/heat resistance. Also most Alkyd and Phenolic resins are moisture permeable, meaning they will allow moisture vapor to slowly pass through them.

https://www.alliedelec.com/m/d/f2adb...1b03fa9565.pdf

[Crist Rigott]

Thanks Kevin.

[Crist Rigott]

Today I re-stuffed C2. I used some solid 22awg 600V wire for each lead to the terminals. I'll let the pictures tell the story.

[Eric H]

I'm still not sure about upping the wattage on resistors. I think I'd rather have a resistor smoke than a flyback or transformer. Granted a half watt or a watt may not make much difference.

[Crist Rigott]

Originally Posted by Eric H

I'm still not sure about upping the wattage on resistors. I think I'd rather have a resistor smoke than a flyback or transformer. Granted a half watt or a watt may not make much difference.

Interesting thought. Though I'll add a "mains" fuse and then there is a .250 amp fuse in the HV cage. Though I'm not really sure what it protects.

All of the modern day 1/2W resistors seem to have very wimpy leads on them. Great for use on PCB's but not so good for point-to-point wiring. Another reason I used 1W, their leads are thicker.

[Crist Rigott]

I finished the power supply. I decided to paint the chassis. I used Rust-Oleum grey primer #254150 and Metallic Matte Nickel #727830. I then used Bar-B-Q Black #7778 on the transformer.

There were only a handful of components to change. I cleaned the tubes and their sockets. I did have to notch one end of the aluminum plate because to went over the choke mounting ear.

I then cleaned all the wires underneath and going to the plug. All done.

[Sandy G]

Man, that chassis sure is PRETTY...Almost as striking as an E.H. Scott chassis..

[bandersen]

Beautiful job but one thought occurs to me. Capacitors can get warm from self heating due to internal ESR plus ripple current. Especially the main B+ filter caps. Sealing them up with hot glue and PVC isn't going to allow them to breathe much and may hasten their demise.