Cold Feet - Videokarma.org TV - Video

Mick AV-8 · #1 11-05-2009, 07:07 PM

Well..did not get my last two caps int the mail yet.. for the HV section in my 1953 Sylvania.
Everything has been recaped and I am getting cold feet attempting to open up the HV cage..to see the two caps in there.

Do you have to remove the CRT to take out the cage?
Does the tube suspend there just clamped at the front..with no support from the cage?
Some one tell me it would be okay to leave those suckers alone and fire it up to see if I even get raster....

***Eric H*** · #2 11-05-2009, 07:17 PM

It's OK to leave them alone and fire it up, there, I told you.

But seriously, you should change them at some point, it might run now but you don't want one to fail and take out the Flyback someday.

If you don't get high voltage in 30 seconds or so unplug it and see if the Horizontal output tube is getting excessively hot.

***Eric H*** · #3 11-05-2009, 07:18 PM

By the way, do you have some pictures posted of the chassis? Might help if we knew what you're dealing with and how it goes together.

Charlie · #4 11-05-2009, 07:53 PM

Mick,

If your Sylvania is like mine, you should be able to leave the CRT in place, however, it does make things easier if you remove it and get it out of the way.

When you remove the cage, everything in the cage will stay in place. It's been several years since I had mine apart, but it seems that the two caps you're likely talking about are underneath the board that the flyback resides on. Once I removed the cage, I think I loosened the supports (or might have even removed them completely) and tilted the assembly to get at those caps.

Not the best of pics I have for it, but this might give you an idea of what it will look like with the cage removed.

Mick AV-8 · #5 11-05-2009, 07:58 PM

Here are some pics..not sure its a 1953 Sylvania Halolight chassis 23 M-1
Andover model chassis 87111-084-075, 20CP4A tube.
does the tube need to be removed to get at the HV cage?

Mick AV-8 · #6 11-05-2009, 08:16 PM

Hi Charlie, your tube neck support is seperate..my HV cage is also the back tube neck support. It has two wing nuts on the sides of the neck support clamp. And two sheet metal screws that hold the sides of the cage down on the chassis. I do not know if the cage can be pulled back or removed with the CRT still in place clamped at the screen? It has been two weeks and I have not received my HV caps from Just Radios..as they left them out of my shipment. But I am just maybe chicken to start digging in the HV section...

Charlie · #7 11-05-2009, 10:11 PM

Our two chassis are obviously quite different. I'm suprised they had different chassis for the HaloLite sets.

Supporting the CRT with only the front bracket would not be wise... especially since you're working on the set and bumping the neck could add even more stress to the front... and likely enough to cause some kind of damage. YOu could probably get away with putting a block of wood under the neck for support... I would think an exact fit would be best.

Removing the tube would probably be a lot easier and safer.

jeyurkon · #8 11-06-2009, 07:33 AM

Quote:

Originally Posted by Mick AV-8

Here are some pics..not sure its a 1953 Sylvania Halolight chassis 23 M-1
Andover model chassis 87111-084-075, 20CP4A tube.
does the tube need to be removed to get at the HV cage?

Your photo matches the chassis layout shown in the service info for that model. Unfortunately they don't give instructions on opening the cage and you'll have to figure it out. The wing nuts are for adjusting the yoke position.

Wear safety goggles, gloves, and heavy clothes when and if you remove the CRT. The heavy clothes are overkill. You're unlikely to break the CRT, but why take a chance.

If you replace the caps, pay attention to the lead dress. It can be important here to prevent arcing. The same for the 5642 tubes.

John

RetroHacker · #9 11-06-2009, 08:33 AM

Personally, I'd just remove the CRT - nothing to be afraid of, just be careful with it. Actually, I'm suprised that you recapped the whole set without removing it... Any time I rebuild a set where the CRT is mounted to the main chassis, I remove it and put it aside. It makes it much easier to flip the chassis around and you don't have to worry about damaging the heavy picture tube.

-Ian

Mick AV-8 · #10 11-06-2009, 11:51 AM

Regarding the wing nuts and the yoke adjustment...anything I should mark up or consider when removing the CRT?
I do not know..but is the yoke adjustemnt done by turning the ring? Seems like the wing nuts and clamp have a slot that allows for the yoke to twist...wondering if I should mark a line on it ant the tube so I can realign it when putting it back.
So just unplug the CRT socket , remove the front clamp and slide the tube forward out of the yoke?
Guidance appreciated...

***Eric H*** · #11 11-06-2009, 01:16 PM

Quote:

Originally Posted by Mick AV-8

So just unplug the CRT socket , remove the front clamp and slide the tube forward out of the yoke?
Guidance appreciated...

That's it basically, don't forget to unhook the high voltage anode, and be careful not to snag the tube base inside the yoke and tear it off.

jeyurkon · #12 11-06-2009, 02:07 PM

Quote:

Originally Posted by Eric H

That's it basically, don't forget to unhook the high voltage anode, and be careful not to snag the tube base inside the yoke and tear it off.

Wrapping a piece of electrical tape around the base so that it goes about half it's width on to the neck will help prevent it from snagging.

John

Mick AV-8 · #13 11-06-2009, 02:17 PM

Can someone explain how the yoke is adjusted?
And what it actually does to the picture.
Again should I make any alignment marks as to where it is and sits..so I can put it back in the exact spot.

Thank guys..I really appreciate your sharing of information!

RetroHacker · #14 11-06-2009, 02:25 PM

The yoke is what "draws" the line across the screen. In the back of the picture tube is an electron gun, firing electrons at the face of the tube. Left by itself, these electrons would fly straight ahead, hitting the exact center of the screen making a real bright dot. The yoke consists of two seperate coils of wire, one for the horizontal, and one for the vertical. These coils are drivin by the deflection circuits in the television, and act as electromagnets. They deflect the beam sideways and up and down, creating the lines of the picture.

So, the yoke needs to be situated such that the picture fills the screen, and is straight. If the yoke is too far back, the electrons get "bent" earlier, and the picture will be the wrong size. If it's crooked, the picture will be tilted. It's real easy to adjust.

When removing a tube with a loose base from the yoke, I sometimes use a wrap of thin packaging tape or similar, to secure the base to the tube and eliminate the risk of catching it up inside the yoke.

-Ian

Charlie · #15 11-06-2009, 02:29 PM

You're not going to be removing the yoke... well... in a manner of speaking. First, you don't have to loosen those wing nuts. The yoke will remain in the support bracket as it is. Even if you remove the bracket when taking apart the cage, everything will go back into the same place once it's put back together. Loosening the wingnuts will allow you to rotate the yoke clockwise or counterclockwise around the neck. As you do this, the picture will turn with the same motion as the yoke. Chances are that it's right where it needs to be. Even if you do need to adjust it, it's just a matter of turning it one way of another to make the picture level on the screen.

Having the yoke in EXACTLY the right place is not as important on a b&w set as it is on a color set. On color, it also plays a role in achieving good purity. On b&w, it's only an issue of tilt.