Roundie picture tube - What wrong with this? Rot? Mold? Delamination?

[lekkerbekkie]

Hi, Just joined the forum and I'm catching the restoration bug. I inherited a CTC20C with a 21FJP22A picture tube (weird combo, seems like a new design married to an older picture tube).

This TV is dead (has 9 bad tubes), but before I start investing in it, I'd like to find out if the picture tube is a lost cause. It has a strange mold-like defect around the perimeter (See pics). I tried searching the forum, but could not find a similar defect. Is this de-lamination of the safety glass? What causes this? Is it fixable or would I need a new 21FJP22A?


STA60052.jpg

STA60053.jpg

Thanks!
Eric

[Eric H]

That is what's called a Cataract, it's the layer of PVA between the tube and the safety glass deteriorating.

It can be repaired but it can be tricky, that one is so bad I suspect it will be one of the easier ones.

Some people use a heat gun on the face of the tube to loosen the bond between the PVA and the glass, that can be hazardous if you heat it unevenly because the tube can implode and spray large chunks of glass all over the place with enough force to kill you.

Another way is to soak the face of the tube in water, sometimes this process takes months to work sometimes a few days.

There's also the Hot Wire method, a small gauge steel Guitar string is heated electrically and used to slice the PVA off.

I'm sure you'll hear from a lot of people on their preferred method.

[jr_tech]

Welcome to the forum! Yes the bonded implosion shield is starting to de-laminate... The common term used for this condition is "cataract". A search on "cataract" should turn up lots of info.
jt

[miniman82]

Welcome to the forum!

The cataract can be repaired, but you have to remove the tube to do it. First put a CRT tester on it, to make sure it's got enough emission to make the cat surgery worthwhile. If not, look for a replacement. To remove the cat, set the CRT face up in a plastic trash bin. Next step varies by method chosen, but I slowly insert wood wedges around the perimeter between the faceplate and tube till it pops off. It can take days for the PVA to release it's hold, but eventually it will let go. Others place the tube face down in a bath of water and let that do it's thing. One tube I broke the glass front off with a screwdriver, but I don't recommend that unless you like glass everywhere...

[ctc17]

NIce 16. Several videos on youtube on how to fix that. I have some and DRH (doug) has some.
As others have said, make that the last thing you worry about. Get the set working good first. Get it going well enough to know the flyback and CRT are good first.

I have almost that exact set sitting next to me. They make a great picture.

[ChrisW6ATV]

Here is one trick: Search this forum for the word "catEract" (notice the mis-spelling). One of the biggest discussions uses that spelling in its title.

[Eric H]

http://videokarma.org/showthread.php...ight=implosion

[mstaton]

looks like a CTC-16 not CTC-20. Almost exactly like mine. Around 1965 or 1966. It's also my avatar.

[DaveWM]

no big deal, get the set working deal with it last. I just did another a couple of days ago, soaked in small kiddie pool face down in a few inches of water after removing the tape around the edge. This makes the PVA pliable enough to dig out some for spaces to insert wedges into. after soaking place face up in a large padded garbage can, in the bright sun on a warm day. I use clothes pins for the wedges. tap them in around the edges, into the spaces that you can dig out. just snug, you can break the glass if you go too hard. walk away for 30min and check to see if still snug, if not tap in again, walk away, repeat this process. You will see stress lines in the pva under the bright sun, looks like shadows of fingers forming around the edge, they will form un evenly at 1st but will eventually form all around the edges and work towards the center. the process starts slowly but will speed up as the fingers get bigger until the lens just pops and you are done. move the CRT into a shady spot and let it cool off. You don't want rapid temp changes, even just using the sun to heat it up. After getting the pva peeled off the crt (it will come up easy if its an RCA tube, zenith is different and does not need the soaking as its already very soft and gooey, the defect on zenith is a green not white or moldy), clean both the crt face and lens. Foam tape can be applied around the edge of the lens, then put it back and hold it on with some clear packing tape, or use silicone caulk around the edge to keep it in place.

Warning, implosion is always a danger, the heat gun method is something I would stay away from, its just not needed.

[bgk283]

hello and welcome, you have the same exact set i started working on a couple of months ago, mines a ctc-16xl and its in sams folder 818. I too had to de-laminate the crt and i like the way Dave does it the best. put it out in the sun and the face will pop off. good luck, Bruce

[marty59]

A CTC-20C would be a valid model with the appearience of the 16Xx's. This chassis started out as a CTC-19 series for the 19" portables but with no pincusion correction and other changes to support the 21" tube demands. This was RCA's last roundie and was generally considered a "value priced" set with carryover parts, bezels etc. This smaller sized configuration is loaded with 6GH8 tubes which can be quite finicky but you can get a nice picture out of it. The correct Sams for the 20's is 837-2.

I don't know if you have access to a CRT checker but it would be good to know the condition of it before proceeding. Be cautious in seperating the socket from its base as they can break loose quite easily. And it's normal to see some Flyback drippings..once the set is running it is always wise to verify the current draw on the horizontal output tube. As long as the CRT is in usable shape, go through the whole set before getting yourself concerned about the cataract. Sometimes a weak tube can perform well so hold off on any rejuvinating as nowadays that's a last resort since supplies are limited.

There's lots of us here to lend you some support!

[marty59]

Here's what a CTC-20C chassis looks like.

[lekkerbekkie]

Thank you all so much for the responses. I can't get over how helpful you all are... You guys are great!

The chassis in this set is in fact a CTC20C and it looks exactly the same as the picture posted by marty59. Being that this TV is (what marty59 believes to be) the last of the roundies... Does it make the set worth anything more?

My plan is to take daveWM's advice and get the set working before removing the shield. Incidentally, this set appears to eat 6GH8A tubes for breakfast... Ha!

[mstaton]

Just looked like one. Very interesting though. Money wise it's not worth anymore than most roudies but probably a little more rare. I have a value priced Admiral roundie($299) from 1966 still using a 64 style chassis. Very basic metal cabinet "table top" model.

[joemama99]

I have a CTC20C set myself,and will tell you that it produces a very nice picture.Very well worth the effort to get it going.