Zenith out of cabinet - Videokarma.org TV - Video

ShartZenith · #1 04-22-2012, 04:38 PM

Got the chassis out of the cabinet today. Broke the cap part of the brightness knob off its base but think it can be epoxyed back together. Bigger problem is the grey plastic ring that encircles the picture tube. It's broken at about 11:00 into many pieces and at the base, 600PM where the plastic mounts onto the chassis with two sheet metal screws. It would be a chore to glue all the pieces back together and not sure it would ultimately hold once reinstalled around the tube. Photos attached. Anyone have a good used one they want to sell?

cwmoser · #2 04-22-2012, 05:10 PM

My 16" porthole has a perfect and pliable CRT mask.
But my 19" porthole mask has some cracks.
Might be hard to find a replacement.
Save all the pieces as you probably will want to refurbish it.

Wonder if anyone here has repaired a CRT mask?

Carl

charokeeroad · #3 04-22-2012, 09:16 PM

Quote:

Originally Posted by ShartZenith

Got the chassis out of the cabinet today. Broke the cap part of the brightness knob off its base but think it can be epoxyed back together. Bigger problem is the grey plastic ring that encircles the picture tube. It's broken at about 11:00 into many pieces and at the base, 600PM where the plastic mounts onto the chassis with two sheet metal screws. It would be a chore to glue all the pieces back together and not sure it would ultimately hold once reinstalled around the tube. Photos attached. Anyone have a good used one they want to sell?

What model did it come off of and what is the diameter as best as you can determine? I have one that's 15 5/8" in Dia. good shape. measured as if you were looking at the set. The forward ring in other words.

(oh! I just looked at your other thread. You have a 19".. sorry don't have that one)

ShartZenith · #4 04-23-2012, 07:22 PM

CW - No answers from others so far. Not only are there about 6-8 little pieces but it has some cracks around the perimeter that are in imminent danger of breaking all the way through. I hate to start cementing this old plastic until I gingerly clean it up a bit, especially the broken surfaces that need to be mated. So what to clean it with and what type of bonding agent to use? Steve

cwmoser · #5 04-24-2012, 06:46 AM

I bet poster Bandersen could come up with some suggestions.
If I remember correctly, my 16" mask was some sort of rigid hard rubber. Many cars have rubber bumpers and I saw an episode of the BBC show Wheeler Dealer where they repaired a rubber bumper using a special product. Unless someone comes up with a better idea, I would try that.

My 19" CRT mask has cracks from front to back and when I remove the chassis again, I'll probably have to deal with fixing it.

Also, I wonder if we can find a metal band that we can form around the mask -- but if we do we would have to ground it to the chassis to avoid possible HV shock.

Interesting problem that needs an answer.

Carl

cwmoser · #6 04-24-2012, 06:51 AM

This has got me to thinking.
Wonder if we can get make a mold out of say plaster paris. Then pour some liquid rubber to make a copy.

Here is an interesting video:
http://www.youtube.com/watch?v=b3eR8...eature=related

Carl

bandersen · #7 04-24-2012, 11:38 AM

Thanks for the link. That's certainly one possibility. It will probably require some experimenting with different materials which can be kinda of expensive though

I've repaired rigid plastic with Loctite 2-part epoxy plastic binder in the past. It's strong, fills voids and can be sanded. I haven't tried it on a bezel yet.

Phil Nelson · #8 04-24-2012, 11:53 AM

Yah, I'd make an effort to repair it if you have enough of the pieces to make it structurally sound. Two-part epoxy would be my choice, too.

Once glued together, if there are some gaps, they can be filled with bondo. Then you can sand as needed and repaint.

Casting a reproduction is not rocket science, but it requires an intact original to make the mold. If you repair your ring well enough to serve as the model for making a mold, then presumably it's repaired well enough to use. An alternative would be to fabricate an entirely new model out of clay or whatever, which exactly matches the original, and use that as the model.

I have made simple one-piece molds in the past. This thing might require a two-piece mold. It's also a rather large object. Neither factor makes reproduction impossible, but they would make it more complicated.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

ShartZenith · #9 04-25-2012, 09:10 PM

Thanks for the suggestions guys. I like the two-part epoxy idea. So now I need to clean up the pieces that are to be bonded and do a little experimenting to see how/if this puzzle will hold. No real work to begin on the chassis until next month when friend Bob will help with that. Went over the chassis with a damp cloth and it looks excellent. Opened up the tuner and it looks clean. I'll be back with more later. Steve

leadlike · #10 04-26-2012, 12:11 AM

It is really hard to find any of those plastic rings that don't have at least one crack in them. I think the exposure to ozone-generating HV accelerates the deterioration of the plastic.

I used JB Weld to fill in a crack on my 16" set, and in about a week, it fell apart again. I used Bond-O this time, and it seems to be holding up. I repainted the whole ring in primer grey, and it was a fine match.

cwmoser · #11 04-26-2012, 06:32 AM

Did you use any reinforcing like say fiberglass cloth in the Bondo?

Carl

Quote:

Originally Posted by leadlike

It is really hard to find any of those plastic rings that don't have at least one crack in them. I think the exposure to ozone-generating HV accelerates the deterioration of the plastic.

I used JB Weld to fill in a crack on my 16" set, and in about a week, it fell apart again. I used Bond-O this time, and it seems to be holding up. I repainted the whole ring in primer grey, and it was a fine match.

ShartZenith · #12 04-27-2012, 09:02 PM

CW,
So you're saying to use bond-O exclusively by itself? Or use the expoxy for the initial gluing of the big pieces then fill in the cracks with bond-O?

cwmoser · #13 04-28-2012, 06:27 AM

Quote:

Originally Posted by ShartZenith

CW,
So you're saying to use bond-O exclusively by itself? Or use the expoxy for the initial gluing of the big pieces then fill in the cracks with bond-O?

Bob, do you think that the epoxy by itself will hold?
Would using fiberglass cloth make it stronger?

I've never done this before.

Carl

Reece · #14 04-28-2012, 06:40 AM

I've used JB Weld with very good results sticking bakelite pieces back together on a radio cabinet. Strange it didn't work on that ring. As to reinforcement, you can use fiberglass cloth or scraps of plastic window screen.

Phil Nelson · #15 04-28-2012, 12:45 PM

After curing, JB Weld is stronger than most materials that you might glue with it.

With this and all other adhesives, the pieces to be glued must be clean. I remember one case where JB Weld didn't hold on a metal surface because it was somewhat greasy (as I discovered later).

Bondo is primarily a filler. I use it to fill in cracks after glueing with something that has greater sticking power.

Fiberglass cloth is helpful to fill in a big gap with bondo after glueing the main structure with epoxy.

Phil Nelson