CTC-15 restoration

[tvcollector]

mstaton, In case you didn't know, this is the same set that was posted under Curbside months back ago, which you posted.. I found a shipper on U-ship to Florida..

http://www.videokarma.org/showthread.php?t=254480

I'm surprised it's still listed on Ebay.. I guess it hasn't been the three month mark yet..


The vertical is starting to look better and better.. Hopefully the Remote issues can be worked out..

I found other threads on here who have had the same issues with this and the 16 chassis.. seems to be common

http://www.videokarma.org/showthread...ighlight=ctc16

http://www.videokarma.org/showthread.php?t=147493

[miniman82]

After seeing the new pics, the linearity looks pretty decent- it just lacks height. I like the idea of replacing the cap across the vert out primary, that could cause issues. Also make sure the lin and height pots haven't drifted, if you haven't already. You're almost there!

[mstaton]

Just a thought, are those TV shows in widescreen? You may be trying to stretch it out too far. Probably not, just thought I'd throw that out there.

[6GH8cowboy]

This is being fed from a converter box, but the vertical is genuinely underscaned. There should be margin to spare. The 24k resistor is dead on. I did notice I replaced the .036 with a .033 so I added another ,0039 across it but it made no difference at all.

I have noticed on a schematic on boxcarcabin.com the Vert lin. control is connected to B Boost only. I'm using the Sams and the Lin cont is across 405v and Boost. Any thoughts.

Basic power supply volts are good and the lytics have been subd. I tried a different tube earlier from another set with no change.

This would be soooo much easier if I had a test jig.

[6GH8cowboy]

Took Miniman82's advice and measured the pots.
Even though they have an affect on the screen without showing a dead spot I find the Linearity pot is open near one end!
Now whats the real value? Sams shows 100k which originally I felt was curious being one end is at 400 volts and the other end at almost 1200 volts, a lot of drop for a 1/2 watt pot. The RCA diagram shows 3.5 meg sourcing from B+Boost only. I measure aprox 5 meg before the hidden break. I also believe the replacement will need to have an insulated shaft/ rotor to prevent arc potential.

Who hazards an educated guess as to the value and where to get one. The closest I have is 3.5meg full metal jacket.

By the way I have a couple handfulls of 500k with a switch if anyone needs some. Nylon shaft.

[mstaton]

I have one from a junk 16 chassis. My sams for the 15 and 16 show 3.4meg. My control reads 2.7meg. If you want it, PM me your address and i'll send it to you.

[6GH8cowboy]

PM sent.

I'm now wondering if this could be the issue with other early RCA's and Clones. I came across other posts about vertical height issues or slight fold over without a real solution and was referred to as a "common problem"

Thanks again!

[miniman82]

It's not all that uncommon, especially for high hours sets. The pots tend to have a high potential (boost) applied ot them, so they attract crud and grow whiskers faster than other ones on the chassis. And as you found out, being under more stress they fail more often.

[6GH8cowboy]

While waiting for a part and other shop work to finish I decided to remove the cataract safety glass. On this one there was not a really hot afternoon and when a front moved through the temp droped and sky became overcast. I heared the glass "TICK" and that was it.

I have removed most of the pieces and I'm down to the last pieces near the center. The PVA is thinner at the center and there is less 'give'. I'm using single edge razor blades as shims at this point and the going is painfully slow.
I'm hesitant to use a hair dryer to help heat it up as most of the face of the CRT is now exposed. There are a few observations I've made.

• Separations showing as an arc break off quite soon
• Separations as showing like fingers result as larger chunks
• The closer to the center the more dificult to do anything with the glass.
• This tube checks really good and had a great picture and the next time I do a cataract removal they'l have to be much worse!

I have a spare clear glass from another set to replace it with.

Any advise would be great. I'm sure that I'm not the first to have to overcome this situation.

[DaveWM]

I am not sure of the problem? did the safty glass break during the removal? is that what you refer to as "tick that was it"

if the glass broke, I would assume you simply over did it with the wedges around the edges of the glass. you need to dig out some of the pva, if its too hard to dig out for space for the wedges then you need to soak in water for a prolonged time.

After digging out the space the wedges (wood closepins) are inserted and tapped in until snug then you let the heat do the work.

[DaveWM]

as the glass begins to let go esp as the contact point begins to really get small you should release some of the pressure by pulling back on the wedges, should should make the last 2" or so not pop so violently (although I have not had it break at that point it still is scary when it lets go).

[6GH8cowboy]

When Ive done this before the wedges get loose as the separation gets closer to the center. I suspect the fail was due to a lone tight wedge when the progres stoped and possibly temperature change came into play. My method is to dig out some pva and gently tap the clothspin wedge until I sense the First tight response after the dull taps of pva intrusion. On a nice hot day the "fingers" appear and travel to the center until the final pop, glass intact.
I have most of the broken material off but the middle section is very slow going and Ive not found a sample even slightly water soluble. or paint thinner, or accetone, or brake cleaner.

The CRT with the fingers was a previous removal on another CRT. The fragment picture is the current project.

[Charlie]

Wow... you guys get cold fronts in South Florida??? A co-worker of mine lives in your county... he makes it sound as if it's summer all year long there.

At least you had another glass. I have a few spare glasses that I picked up years ago in case of breaking one. So far, I've had to do cataract surgery three times. I've been fortunate that the cataracts were so bad, the safety glasses came right off with little or no effort.

[6GH8cowboy]

Back to the project. Full vertical courtesy of a replacement control via MSTATON (THANKS THANKS THANKS) , new spare glass after a miserable removal of the original.

Now time for a complete registration and purity setup and touchup the grey scale tracking. Awaiting for a remote unit that may be a better match and were good to go.

[tvcollector]

Looks really good.. Great job Dave...