Sylvania 1-076 arrived! - Page 10 - Videokarma.org TV - Video

jr_tech · #**136** 02-21-2010, 10:10 PM

"I'm going to ring test the yoke and perhaps swap the horizontal leads to see if the focus issue moves to the other side of the screen or stays put."

That experiment should be interesting!

"20KVDC, max pulse 40KV scope probe"

6015A?

jr

jeyurkon · #**137** 02-21-2010, 10:59 PM

Quote:

Originally Posted by jr_tech

"I'm going to ring test the yoke and perhaps swap the horizontal leads to see if the focus issue moves to the other side of the screen or stays put."

That experiment should be interesting!

"20KVDC, max pulse 40KV scope probe"

6015A?

jr

Yes, but not mine. I borrowed it.

John

jeyurkon · #**138** 02-23-2010, 11:11 PM

I ring tested the yoke with a Sencore LC101. If the yoke is good it's supposed to give 10 rings or more. I got 9 max. Not definitive.

The DC resistance is supposed to be 36 ohms. I measured 47 ohms. The yoke is a bit different in that the horizontal windings are in parallel. This would mean that each coil should be 72 ohms. If I assume the difference is due to one coil, then it would have a resistance of about 135 ohms. Quite a bit different.

I swapped the horizontal leads and while the raster reversed, the focus problem remained on the same side. This, along with trying to rotate the focus magnet and moving to different positions has no effect on the problem leads me to believe that the yoke has a problem.

Another clue is that it appears that someone replaced on of the horizontal leads with HV wire. It has a polyethylene core and a plastic jacket. All the other leads are fabric coated.

Normal

Reversed

The ringing is probably due to the long jumpers I used to connect the yoke.

Notice that the keystoning is the same for both. If it was a supply issue it should be reversed when I reversed the leads.

It looks like I need to search for a yoke.

I would need a Sylvania 100-0001 or a 100-0002 and a horizontal choke 241-0002. The second version has a center tapped yoke instead of parallel windings and thus needs a center-tapped choke. I'd call it a transformer, but they call it a choke.

The Merit numbers would be MD-13 for the yoke and C-2980 for the choke.

If anyone can provide Thordarson or other cross reference numbers that would be great. The actual parts would be even better!

John

jr_tech · #**139** 02-23-2010, 11:44 PM

If you rotate the yoke 90 or 180 degrees does the area of poor focus follow the mechanical rotation of the yoke? If it still stays on the right hand side of the tube, perhaps some steel part near the neck of the CRT is magnetized ?

jr

jeyurkon · #**140** 02-23-2010, 11:55 PM

I can probably only rotate the yoke over a +/-15degree angle. But that's probably enough to do the test you suggest.

I don't think it's a magnetized part of the chassis. The point at which the focus gets bad follows a vertical line. I wouldn't expect it to follow a straight line line if it's the chassis.

It's a good test though, if the bad focus rotates too, then it has to be the yoke.

John

jeyurkon · #**141** 02-24-2010, 12:10 AM

I have a Sylvania yoke that is similar to the one in the set. I just did a ring test on it and got 25 rings. Quite a bit more than the one in the set.

Sencore says to make a shorted copper loop and place it around the yoke windings. If the number of rings doesn't change by a lot, then there is probably a shorted turn.

I'll have to try that along with rotating the yoke over its limits.

But, not tonight...

John

jeyurkon · #**142** 02-24-2010, 11:42 AM

I finally scored a hit with Moyer's. They have a RAM yoke that will replace either the 100-0001 or 100-0002 Sylvania yoke. I don't think that there are many of these around so it won't hurt to have one on hand even if it turns out that the yoke is o.k.

John

miniman82 · #**143** 02-24-2010, 05:14 PM

Sorry I don't have time to read this lengthy (and great) thread, but that looks like an h-linearity problem to me. See how it's all stretched out on the right hand side in the second pic?

jeyurkon · #**144** 02-25-2010, 12:01 AM

Quote:

Originally Posted by miniman82

Sorry I don't have time to read this lengthy (and great) thread, but that looks like an h-linearity problem to me. See how it's all stretched out on the right hand side in the second pic?

That's true, but is only due to the temporary connection by the use of jumper leads. It's not part of the focus problem that I'm concerned with.

John

jeyurkon · #**145** 02-25-2010, 12:07 AM

I tried rotating the yoke over the limits of it's travel as suggested by jr_tech. I used a dot pattern to judge whether the focus problem followed the rotation or not. It follows the yoke.

I'm getting more and more convinced that the problem lies with the yoke. I should find out soon, when the RAM yoke arrives.

John

jeyurkon · #**146** 02-26-2010, 08:57 PM

I received the RAM replacement yoke today. I tried ring testing the horizontal and saw 33 rings as opposed to the 9 rings I saw with the original yoke.

I don't think I'll get a chance to install it this weekend. The core is loose on this yoke also and I'll need to fix it in position before I install it.

John

miniman82 · #**147** 02-27-2010, 10:49 PM

Hope the new one fixes the problem, you're so close to having a very nice picture!

jeyurkon · #**148** 03-03-2010, 12:18 AM

I made a couple of attempts at making rosettes. The one on the left was done with a clear epoxy that is close to mahogany in color. I did spray it with brown mahogany lacquer.

The one on the right is made with a white paste epoxy. I think I'll try dying the epoxy to the right color, then give it a coat. Although it does kind of match the aging of the cabinet as is.

I need to trim the rosettes a bit to remove the excess epoxy.

The photo on the right shows the rosettes before coating.

John

jeyurkon · #**149** 03-06-2010, 09:27 PM

I finally got around to swapping the yoke. Guess what, it was the yoke that was causing the focus issue!

I'll post some photos as soon as I get it finalized. In spite of being careful I managed to swap the two horizontal leads. I left them long in case I did something stupid like that. There's a bit of ringing that I hope clears up when I dress the leads.

The yoke that was in the set is the wrong yoke. It was a 100-0002 and the manual says that you cannot use it with an output choke that isn't center tapped without danger of breakdown in the yoke. That must be what happened to it. The manual warns that servicemen have been replacing the 100-0001 with the 100-0002 when they shouldn't.

The yoke I put in though is made just like the 100-0002. Moyer said that RAM says it can be used for either yoke. It came wired as though it was a 100-0001, but internally it's like the -0002.

Does anyone have a RAM catalog? I'd be interested in knowing what it says about a Y70F25 yoke. It's to replace a 100-0001 yoke in a 1-108 sylvania chassis.

I'd feel better about using it if I could find a center tapped choke to go along with it. Can anyone tell me cross reference numbers for a 241-0002 choke for this set? I've yet to figure out why they call it a choke instead of a transformer.

John

John Folsom · #**150** 03-06-2010, 10:29 PM

John,

Thats fantastic! Way to go. You may find the ringing is better when you swap the yoke leads, as often the yoke has a balancing capacitor across one of the two horizontal windings.

The Y10F25 yoke is speced at 25mH (H), 50mH (V), 27 ohms (H) and 60ohms (v). RAM does not list a replacement for the 241-0002 (flyback transformer, not a choke)

Thordarson, Stancor and Merit do not list a replacement. Must be an oddball flyback...?

The Thordarson cross ref. lists the 1-108 chassis as using a 113-0010 flyback, with a HVO-50 replacement. Is this a mistake in the Thordarson listing?