Sylvania 1-076 arrived! - Page 11 - Videokarma.org TV - Video

jeyurkon · #**151** 03-07-2010, 12:17 PM

Quote:

Originally Posted by John Folsom

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?

I was wondering about whether the balancing capacitor would do that, but it goes against my grain to think that a one-port passive network would behave that way. There must be enough stray capacitance to make another connection, turning it into a two-port. It does seem to behave as you said though. At least the original one did so I hope this one does too.

Thordarson didn't exactly make a mistake. The RF HV supplied sets don't fit neatly into the charts of Thordarson, RAM, and Merit. The 113-0010 is the RF HV transformer and is listed for the Horizontal output in the Merit catalogue also, even though that's not what it is.

I wouldn't call the 241-0002 a flyback because it doesn't use the retrace (flyback) to generate the HV. It looks just like a filament or audio transformer. All four of the manuals that I have for this set call it a choke, including the SAMS. I assuming that they have a reason to call it that. It hurts my head to think about that part of the schematic.

If you want to peruse the service manual you can see it at:
https://www.msu.edu/~yurkon/Sylvania_9-2_Sup1.pdf

Thanks for pointing out the 113-0010 being called a flyback. I now have cross-reference numbers to search for a spare.

John

John Folsom · #**152** 03-07-2010, 12:43 PM

John, I am afraid I am a poor student. I had forgotten your Sylvania was one of those very interesting RF HV supply sets, and would use s separate transformer (choke?) to drive the horizontal coils. I also note on the schematic the yoke coils are wired in parallel, so my supposition about the balancing capacitor is probably not valid. But hopefully when you reverse the leads on the yoke, your ringing issues will get better.

Good thing you don't have troubles with the RF HV coil, as some of these don't have a replacement.

John Marinello · #**153** 03-07-2010, 01:26 PM

Quote:

Originally Posted by jeyurkon

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

Any thought of making a wood one? If you could make a study enough die, (maybe with jb weld?) you could probably make one the same way the originals were made. Maybe cut a circular piece of mahogany, soak it in water for a while, and force your die over it, maybe in a vice, and let it sit until the wood dries?

jeyurkon · #**154** 03-07-2010, 03:10 PM

Quote:

Originally Posted by John Marinello

Any thought of making a wood one? If you could make a study enough die, (maybe with jb weld?) you could probably make one the same way the originals were made. Maybe cut a circular piece of mahogany, soak it in water for a while, and force your die over it, maybe in a vice, and let it sit until the wood dries?

That would be cool! I think I might try it.

John

jeyurkon · #**155** 03-07-2010, 03:16 PM

Quote:

Originally Posted by John Folsom

John, I am afraid I am a poor student. I had forgotten your Sylvania was one of those very interesting RF HV supply sets, and would use s separate transformer (choke?) to drive the horizontal coils. I also note on the schematic the yoke coils are wired in parallel, so my supposition about the balancing capacitor is probably not valid. But hopefully when you reverse the leads on the yoke, your ringing issues will get better.

Good thing you don't have troubles with the RF HV coil, as some of these don't have a replacement.

The yoke that was in the set, and the replacement, are both made as you described with the coils in series and a capacitor across one coil. The 100-0002 yoke that is in the set was meant to be used in a center-tapped mode. The schematic shows the 100-0001 yoke where the windings are in parallel. That's the yoke that should have been in the set.

So, your comments really do apply.

I wonder why there are replacements for all of the other transformers and coils, but not the horizontal output thing?

John

John Folsom · #**156** 03-07-2010, 05:42 PM

John, if reversing the yoke leads does not work, I wonder if you could try rearranging the yoke to operate in parallel, without the balancing cap? How does the inductance of the replacement yoke compare with the original? What Sams Photofact is your set in?

These RF HV supply sets for the 10" and 12" CRTs were oddball sets even in their day, and I suspect the Thordarson/Merits/Stancors of the day did not consider it worthwhile to make these low volume parts.

jeyurkon · #**157** 03-07-2010, 06:24 PM

Quote:

Originally Posted by John Folsom

John, if reversing the yoke leads does not work, I wonder if you could try rearranging the yoke to operate in parallel, without the balancing cap? How does the inductance of the replacement yoke compare with the original? What Sams Photofact is your set in?

These RF HV supply sets for the 10" and 12" CRTs were oddball sets even in their day, and I suspect the Thordarson/Merits/Stancors of the day did not consider it worthwhile to make these low volume parts.

The folder is number 11, set 96. I find the SAMS more difficult to read than the Sylvania or Wallace schematics.

The inductance of the RAM yoke is the same as the Sylvania. If I were to rewire the coils in parallel the resulting inductance would be somewhere between 1/4 to 1/2 the original inductance, depending on how much mutual inductance there is between the two.

I'm doing laundry tonight and when I do laundry I don't have access to the trap door to my basement so I won't get to try it tonight.

Roger Dreyfoos sent me some info from a RAM guide to yokes that is pretty interesting. It talks about residuals fields in some that need to be eliminated. I thought that was my problem, but now I think it's just a bad yoke to begin with, but no shorts.

It has an iron wire winding to form the core, that likely accounts for the low ring test. I don't think there's a short because both half coils test the same for inductance and number of rings. It probably doesn't shield well against the focus magnet which causes a rotation in the raster.

The yoke also appears to be deformed, I'm not sure why that is, but it is also off axis from the housing. The off axis problem is just the way it was assembled.

It also appears that it is not cosine wound, which doesn't help the focus either.

I'm still going to check it out with a hall probe, but using the digital compass on my watch suggests that the residual field is less than the earth's field. I don't think a residual field is the problem. If it turns out to be stronger than that, I might try degaussing it.

John

jeyurkon · #**158** 03-08-2010, 11:46 PM

This is getting to be more involved than I expected.

I checked for residual magnetism in the yoke. The earth's field in Michigan should be about 0.57 Gauss. The field along any axis in the yoke was 0.5 Gauss or less so it doesn't appear to be magnetized. At least not enough to cause any problems.

The first photo shows the rear of the yoke. You can see the bottom h-coil is distorted. The second photo shows that it doesn't appear to be cosine wound. The third photo shows the ends of the coils not being perpendicular to the axix. I think these all add up to the bad focus issue.

If you look through the mounting slot you can see the iron wire that forms the core.

I shortened the leads on the yoke and corrected the reversed horizontal lead connection. The ringing is terrible.

After getting the right image by swapping the leads, the blue lead was not connected to the hot side as both the schematic says and the data sheets indicate. The horizontal output choke appears to at least had one lead lengthened. I don't think it's possible for them to have reversed the output leads and have it work at all.

As John Folsom mentioned, the coil that has the capacitor across it should be on the hot side, which it isn't now that I have the right image. I'll have to move it to the hot side and see how well it works.

The data sheet with the RAM yoke says that when they supply the network with the yoke it's not connected. In this yoke it was already connected. They also give instructions for balancing the yoke if there is still ringing after properly connecting the supplied network. If connecting the capacitor to the other coil half doesn't eliminate all the ringing I'll have to build their little "X" checker device. Just a variable resistor and capacitor in series.

I don't want to run the set while it's in this condition, so I'll take photos once I get it working better.

In spite of the ringing, the focus problem is still gone.

The yoke appears to have been made by Chicago. It looks just like their TY-1 yoke.

John

jeyurkon · #**159** 03-09-2010, 11:00 AM

You can see the Chicago TY-1 here: http://www.bunkerofdoom.com/xfm/CHICAGO1954/004.jpg

and the similarity to the Sylvania 100-0002 is very strong.

The data is here: http://www.bunkerofdoom.com/xfm/CHICAGO1954/003.jpg

and the TY-1 is not cosine wound. It has an iron wire core just like the Sylvania. Not too surprising that focus was so touchy. Especially if they stretched the design to go from 53 degrees to 70 degrees.

John

jeyurkon · #**160** 03-09-2010, 11:47 PM

I moved the balancing capacitor from its original position to the hot side of the yoke. I didn't take any before pictures because the ringing was so severe I was afraid it might damage something.

I haven't aligned the horizontal section or do any serious adjustment of the vertical. I was mainly interested in seeing whether the ringing would be reduced and if the focus would be good. The focus looks good, there is still a little bit of ringing.

The balancing cap in the original yoke was 47pf and the one in the RAM replacement is 68pf. I'll probably use a variable cap first to see what value works best.

Then I need to shim the yoke. For some reason it tilts down a little when it's mounted in the saddle.

Then I'll align the horizontal. That will take care of the curvature and reduce the flagging. There was always some flagging unless I was receiving an over the air broadcast. No chance of that now. There may be a minor problem in the sync separator.

John