I'd keep that blue lead too - never know when it might come in handy.

Which one? The picture quality of the 65" WD-65831 I bought last year is stellar, and I got it for a song at Best Buy.

The WD-60C9. Not as high end as the 831 series, but I'm very happy with it. With it set for natural, the color is quite good. Though the blues tend to be quite electric in some scenes. I'm tempted to try the advanced set up.

I wish I knew where the vertical center of gravity is. Since I have it mounted high enough to go above the Sylvania, I'm tempted to tilt it forward by 10 degrees.

John

Whoops, just looked at the back and it's actually a WD-65735. Went to the Mitsu site, they now have 82" sets! Looks like it's trade up time, huh? :D

Maybe if you have a 20ft deep living room! :D

John

Yeah, no doubt!

Anyhow screw HD, back to watching South Park on the Philco! :)

Here's a thread where making a mold to reproduce an item like that rosette is explained.

http://www.videokarma.org/showthread...highlight=mold

Duplicated

I've added a circuit to supply the screen bias needed for a 12LP4, that uses the existing 170VDC supply and a 135 V. rms tap. It comes out to 255 VDC which is really close to the 250 v typical G2 operating point of the 12LP4.

After replacing the crt connector and adding the circuit I tried operating it with the 10MP4 to make sure I didn't mess anything up. It works fine. In fact, I used to have a minor problem with a crawling horizontal and vertical distortion in the image that I had thought was from the damper tube filament transformer which is mounted near the neck of the CRT. This problem has disappeared. So has the sync buzz you get when tuning, or have text displayed on the screen. In fact the sound quality is dramatically better.

There is no reason the circuit I added should have any effect on either the sweep or the sound. Guess I shouldn't complain though.

The next step will be to try the 12LP4. I'll take photos of the circuit addition when I do the test.

I got rid of my old rear projection set and mounted a DLP on the wall leaving space under it for the Sylvania console. I've attached a photo of how it'll be set up. The cabinet is empty at this point.

John

Swiss Army Knife
 

I've attached a photo of the booster circuit I added. It's on the board with the orange drops.

Close, but no cigar. :tears: Yet. :thmbsp:

I tried mounting the 12LP4. I raised the scanning bridge to the next higher set of holes which centers the yoke on a 12" CRT. However the 12LP4 is 3/4" longer than a 12VP4. The yoke has a large adjustment range to accommodate both the 10MP4 and the 12VP4, but not enough to handle the 12LP4. I was about to give up and consider staying with the 10MP4 and then having to decide whether to mount it in the 1-128 cabinet or the 1-076 cabinet. 10" would make most sense in the 1-076, but the 1-128 cabinet is the one our family kept.

But, not all is lost. It turns out that the chassis has another set of holes for a 12" CRT located 3/4" farther back that would make the 12LP4 fit perfectly. This must be the Swiss Army Knife of chassis. It was used for a large range of sets including one that used a 16LP4 CRT (at least the bridge was). The 16LP4 version has a boost circuit for the screen that uses a 6X4. There is a hole already punched for it in the bridge. I could have gone that route, but I would have had to reroute too many wires. It would have been a lot of work and the work would have been obvious. So, I used a silicon diode version of the circuit that I could hide underneath.

But, the bell of the 16LP4 is 4 inches longer than the 12LP4. I'm guessing but it seems that they had designed the chassis to be able to use the 12LP4 but never built them with it. The 12VP4 was probably less expensive, especially since they could leave out the 6X4.

When I do move the bridge back, the cross brace may not have a set of holes for it. It had one for raising the bridge, but I suspect there won't be a matching location for both raising and moving the bridge back. I may have to make a different cross brace. Not a big deal since it's just a flat strap with a bend and each end.

John

12LP4 working, but need advice
 

I installed the 12LP4 tonight by moving the bridge to the next set of mounting holes back. By the way, there are another set of holes that would accommodate a 16LP4. That's really stretching a design.

I will have to make new side straps because of moving the bridge back. They're 3/4" too short now. To my surprise, the cross brace still fits.

The raster was shifted to the left. I was able to center it with the horizontal center control, but the raster is out of focus on the right. I had to greatly reduce the focusing field to get it to focus, compared to the 10MP4.

I've included a photo of the dot pattern to show the focus, though it's obvious in the movie photo.

I just noticed that the focusing magnet is pretty far off center vertically. It's centered horizontally. This doesn't seem to match the focus issue.

The yoke is very slightly off axis. It's such a small amount that I can't believe it's the cause. I'll try moving it to see what happens.

The GE data-sheet for a 12LP4 says the center of the focus magnet should be 4-1/2" from the reference line. The Sylvania data-sheet for a 12LP4 says it should be 3-1/4" from the reference line. Mine is 3-1/2" from the reference line. I wonder if I should move it back a bit.

Any suggestions as to what might be causing the left shift and the bad focus on the right would be welcome. It seems to be unaffected by the ion-trap position.

John

I think that I also see some keystone from left to right (yoke alignment?) or perhaps some voltage shifts? Are power supply voltages, boost, HV constant ? or do they change with the horizontal position of the beam?

jr

The key-stoning was there with the 10MP4 also, but it didn't have the focus issue and it was centered horizontally. I'll have to check the supply and the boost. The HV will be constant if the power supply is since it's an RF oscillator type. At least it wouldn't be coupled to the horizontal.

It could be the power supply. Since I had to make a large horizontal center adjustment, and the pot that does that also drops the 180V to supply 170V to other sections, it could now be affecting the 170V that I boost to 250V. The 170V is also supplied to the vertical output stage.

Until I'm able to secure the CRT I won't be able to do any measurements under the chassis.

It's probably not related, but right where the screen gets blury is where the right edge of the scan stopped until I recentered it.

John

I scoped the G2 voltage and there is minimal ripple. Perhaps a volt. The G2 is +254V. This shouldn't account for the focus problem. Also, since this is derived from the +180V supply, it shouldn't be causing the keystoning either. I can't get to the -125 supply yet to check it, but it could have ripple causing the keystoning.

The gun does not appear to be a slashed field type. It doesn't seem bent either, but I can't see enough of it to be sure either. This is a rebuilt 12LP4 and the gun is different than the original type. If the end is offset like I see in some diagrams, that might be causing the left shift that I'm having with the raster. I've tried centering the focus magnet better and playing with the yoke with minimal improvement.

Since the gun is different I started to wonder if I needed to use a single field trap instead. The instructions that came with a Miller adjustable single field trap says that CRTs up to 10" or 12" having a straight gun, generally use a double ion trap of 38 gauss. I think by straight gun they mean one with a slashed field.

Then they go on to say that CRTs of 14" to 17" having a bent gun, use a single ion trap of 35 to 45 Gauss. Larger CRTs use a single ion trap of 45 to 55 Gauss.

Since it doesn't appear to be a slashed field type I decided to try a single field type. I had to adjust the field down to 35 Gauss for best results. This is the same strength as the double field trap that I have. With it adjusted to the best position I wasn't able to do any better than I did with the double field trap. With both of them I have to butt it up against the base. I get the impression that it might be better to even move it over the base. Perhaps the field is too strong, but I can't adjust the adjustable trap any lower than 35 Gauss.

The HV is at 8.8KV. The manual says it should be between 9.5KV to 7.5KV depending on the brightness setting. I heard some corona in the coffee can today so I've got to find that. I've suspected it in the past, but I've never been able to see it. I was also afraid of getting my nose too close.

I have another 12LP4 that is rebuilt that I can try. I noticed a strange charging effect when I used the single field trap. I'd adjust it, it would be o.k. for a few seconds and then drift. This didn't happen at the best position though.

If it's a matter of not having the slashed field type gun, I have one unrestored set that has a good original 12LP4 in it. I hate to take it out but I may have to eventually try that.

John

Perhaps it is indeed a straight gun...Do you get any beam to the screen with NO magnet?

"I have one unrestored set that has a good original 12LP4 in it. I hate to take it out but I may have to eventually try that."

It seems that many times the most difficult experiment yields the most useful data!

Since you mentioned charging effects, I had another terrible (perhaps far fetched) thought about the key-stoning/focus... since the tube is not aluminized, is the landing energy of the beam constant as it travels across the screen ? Is it possible that the phosphor surface discharges somewhat during retrace? :scratch2:

jr

O.K. I do get a raster with no magnet. I tried the other rebuilt CRT and it behaves the same way. The raster is best without the magnet. However it is still badly focused on the right side.

The keystone is much reduced without the ion trap. I did have a keystone with the 10MP4 also. I suspect it is the -125V supply not being rigid enough, but I haven't tested it yet.

In defense of your odd theory :thmbsp: when I had the keystone effect pretty bad with the 10MP4 I thought about charging since the raster would move if I got my hand near the front of the CRT. I blew on the CRT expecting moisture to drain any external charging. The raster blew up and disappeared for a second then returned with only a tiny keystone. I think the small keystone is a supply issue.

I did some research and the only way I can see that I could get a raster without an ion trap is if G2 and G3 are at the same potential. I think this would be extremely unlikely. Especially for both CRTs.

I will have to try the old 12LP4 that is in a Sonora that is further down the restoration queue.

BTW, I did look up the specs for a 12LPC. Although it is aluminized, from the factory it still requires a dual field ion trap.

I also found this page where they converted a set from a Triode to Tetrode CRT. They had to reduce the focusing field, which I also observed.

Something else that is happening now is that I get a bright spot for a couple of seconds after turning the TV off. With a gun that requires an ion trap, the electrons have to have the right velocity to make it out of the gun. As soon as the HV drops they get lost. But the straight gun without a trap doesn't filter by velocity

John

I would try moving the focus magnet. Specs for a 12LP4 call for a double-field ion trap, but once they're rebuilt, it seems anything goes. All of the rebuilt CTRs that I've seen used a single-field ion trap. For that reason, I would ignore the focus magnet orientation specs and adjust it for best pic.

Thanks for the suggestion. I tried moving it further back and that helped with the centering, it improved the focus a little at the top and bottom, but the right is still bad.

It could still be a geometry problem, but that it no longer requires an ion trap worries me. Unless the vacuum is extremely good I'd eventually get an ion burn.

John

No pictures, yet I don't have any time left to work on it today.

I tried the 12LP4A from the Sonora. It was made by NU-Videon or something like that. It was better, but basically behaved the same except that it really does need an ion trap.

Using the double field trap I wasn't able to adjust it properly. At the brightest position there was a shadow. It was not as bright at the position that got rid of the shadow, but the focus was good.

I then used the single field trap that was on the tube. This tube really does require a double, but the single field gave the brightest image without the shadow. The CRT is dim and blue opposite the anode connector. It looks a lot like the damage described in the article I posted about adjusting ion traps where the beam hits one of the electrodes and sputters material on to the screen. I fear that's a result of it's being used in the Sonora with a single field trap.

I think the offset raster and bad focus on the right is a geometry problem. I earlier posted that I was surprised that the cross brace still fit after moving the bridge back. Well, it is slightly off shifting the bridge to the left. I'll need to make a new brace.

It may also account for the bad focus on the right. When I mis-adjusted the ion trap I could get a good focus everywhere, dim raster though. This makes it seem like a depth of field problem. When the ion trap is mis-adjusted, only a small portion of the beam exits the gun lowering it's acceptance. That is, there is a smaller range of angles of electrons leaving the gun. This gives a larger depth of field. With a small depth of field the focal plane has to be aligned properly to be in focus everywhere. With a large depth depth of field the focal plane can be tilted with respect to the screen and still have a good focus.

This is conjecture and I'll have to see what happens when I get the bridge back into its proper position.

I'm still worried about the rebuilds not using an ion trap any more though. I wonder how long they would last this way.

John

I tried the used 12LP4 from the Sonora again, mostly to take a photo and try having the bridge in the correct horizontal position. That's the photo on the left. Ignore the vertical non-linearity, my bad.

The bridge position didn't help the focus. It did turn out to be related to the depth of field of the focus of the beam, but not because of a rotation of the screen around the focal plane.

You'll notice a bluish stain in the bottom right corner. This is opposite the HV connector. The HV connector is on top in the Sonora so this stained region is outside of the normal scan in that set. In the Sylvania I have to have the connector at a 45deg angle so that's why it shows up here. Its a really odd stain/ion burn because when you look at it closely you can see that the phosphor grains are coated on one side. I have no idea how this occurred.

The RCA data sheet for the 12LP4 gives more information than the others. It gives focus and ion trap strengths for 9KV and 11KV. The proper field strength for the ion trap at 9KV is about 14% less than it is at 11KV. That means it should be 30 Gauss instead of 35 Gauss. That's probably why I can't adjust the double field ion trap properly because I'm at 8.8KV. If I try this CRT again I'll make a shunt for the trap to reduce its field. I should be able to do at least 9.5KV with the Sylvania. That's supposed to be less than the peak value obtainable. Perhaps I missed something when I worked on the HV section. Maybe the RF transformer is getting lossy. The Sylvania manual also says to try different 6Y6 tubes since they're not all created equal. Or, maybe it thinks it's a Philco. ;)

Since the focus field should be smaller at 9KV and it should be smaller also for a tetrode CRT than a triode CRT I decided to try to reduce the focus field more than I was able to easily do before. I was afraid that I would have to add more shunts, but there was still some adjustment room left.

Now the focus isn't perfect, but it's fairly uniform across the screen. There is some astigmatism. The focus magnet is close to the yoke at the moment. I will move it farther back which should help and eliminate the shadowing on the left.

The Sylvania is capable of better resolution than you see here, though it's not bad for a set of this vintage. It's mainly a focus problem. If I can get the HV up to 11KV I think things will look much better.

They did a really good job of rebuilding the two CRTs I have. They have excellent emission and are nearly identical in performance. My only concern is that they no longer use an ion trap.

John

Great progress! :banana::banana:
Wow what a saga! So where did the Horizontal position pot end up ... still pushing the raster hard to the right? Another 1 to 2 KV should sharpen things up a bit if you can get it and still get enough horiz and vertical scan. Does the "shunted" focus assembly produce a fairly uniform field?

jr

The pot is pretty much in a neutral position now. Basically where it was for the 10MP4. I have more than enough scan width left over in both horizontal and vertical.

I don't know how uniform the focus field is. I'll have to borrow a Gauss-meter. I didn't add any shunts. There are two versions that this same chassis uses. One has two adjustable shunts and another has only one. This one has two so it probably helps to keep the field uniform.

John

Hey! My Philco resembles that statement. :smoke:

Scotty is a great guy! He says the SW30 is the correct gun for a 12LP4, but it is a straight gun and should only be used for an aluminized 12LP4. Since my CRTs aren't aluminized a bent gun should have been used.

He is willing to rebuild the two CRTs again for only the cost of rebuilding the two bent guns. This is more than reasonable since I would have had to pay the rebuilding costs for the guns anyway since bent guns aren't available.

I can highly recommend Scotty for any rebuilding. Also, the emission for the two CRTs were perfectly matched and in my opinion atests to the high degree of control that he has in the rebuilding process.

John

I was wondering if I'd get a rise out of anyone. :D

"rebuilding the two bent guns"

Wow! How does he get the old cathode out? Grind/cut away the retainer ring? Or perhaps he somehow replaces the whole cathode/grid cup assembly and re-aligns it? :scratch2:

Hats off to anybody that can do this.:thmbsp:

jr

He has someone else do it.

When I took mine apart I gound the three spot welds. That left three small holes in G1. I don't think that would affect the operation.

I hope Bob or John correct me if I'm wrong, but for rebuilding their 15GP22 guns Bob edm's the retainer/cathode holder out. That leaves G1 intact. I think they made a tool to stamp out new retainers.

John

I swapped the audio and HV 6Y6 tubes and the HV went from about 8.8 KV to 10.2KV. The audio has crackling noises so it's pretty clear that there is leakage in that 6Y6.

That helped the focus issue a bit. It's livable, but I think I may have a problem with supply ripple or ringing in the horizontal section. The vertical focus is quite good most everywhere now. But the horizontal is off. When I reduce the width to what it was with the 10MP4 the horizontal resolution improves. It's not just a magnification issue because the test pattern resolution improves.

Something else I meant to ask about; when I received this set the yoke was 5-10 degrees off axis. I thought it was just misadjusted, but after restoring the set that was the position it has to be in for the scan to be horizontal. It's unchanged between the 10MP4 and 12LP4.

Is it common for yokes to need to be adjusted this way? If not, what could cause it?

John

I forgot to mention that after getting the HV back up to where it should be, the corona sound got louder and I do smell ozone. It doesn't happen with the coffee can off though. It looks like there is a discharge between the cap of the 1B3 and the can, based on burn marks on the paint. The cap seems smooth, but I guess I should try polishing it more.

About the yoke rotation, the yoke is in a steel cradle that is half a tube. A solenoidal magnet will rotate the scan. Since the focus magnet was very close to this it may have magnetized it and it could be acting like a solenoidal magnet. I'll have to try degaussing it the next time I have the CRT out.

The vertical centering magnet assembly was falling apart from age, so I made a new holder for it out of fish paper. The red paint on the ring indicates the North pole of the magnet.

The disk on the left is the original one.

John

Since I had to move the bridge back to accommodate the 12LP4 I had to make longer brackets. The second one from the bottom is the original one. The bottom one is one that I bent from sheet stock. The third from the bottom is one that a machinist friend made. It looks the nicest, but even though it is the same thickness, it is too stiff to bend. I may have to try annealing it.

The top object is the original cross brace and the one below it is the one I made. There is very little difference between them other than the bend angle and a slightly different hole location.

John

I also had to make a longer strap. I found a piece of strapping in a dumpster that was the right width and thickness. I cut a piece of steel for the retaining end and took a 10-32 stainless socket head cap screw, but the head off, and beat it with a hammer to make the other end. These parts are shown in the first photo. The second photo shows the original strap. The next two show the ends of the strap after spot welding the pieces on and the next two show the completed chassis after assembling the parts.

The original CRT had a brown paper strip glued around the CRT under the strap. It was also glued to the strap. I guess this was to provide some minimal protection for the CRT and keep it in place. Although not as original, I used cork. It works well and holds the CRT securely. I'll trim it up after I am satisfied with the CRT adjustments.

You can pick up a resistance welder on eBay for almost nothing. They come from China. I can't figure out if they are a knockoff of the ones that Hobart and Miller sell, or if they supply Hobart and Miller. If you do get one off of eBay, don't expect it to work out of the box. It takes some adjustments.

I also wanted to have a fire extinguisher nearby in case a spark caught something on fire. If you have a cat, don't expect the release pin to be in the extinguisher when you pick it up. I can't figure out where Schatzi has hidden it! :dunno:

John

Cabinet work
 

Since I have to replace some missing pieces of the cabinet I needed to learn how to do veneer work. After doing some reading using a heat activate glue sounded like the easiest. It's safe, water based, and you can do it in your living room. You can align pieces without them sticking until you are ready.

I missed the first photo. I forgot to load the film (CF card).:withstpd:

I taped the veneer down to keep the glue from getting on the face. The veneer is cut larger than the plywood. I've already applied the first coat of glue to the plywood in the first photo, but I didn't apply it to the veneer yet since it's a paper backed veneer, it won't require two coats. The glue needs to dry for 20 minutes.

I was surprised at how easy this process is.

In the second photo I've applied glue to the veneer and the second coat to the plywood.

The third photo shows the veneer setting on top of the plywood ready to iron on with medium-high heat.

The last photo shows the finished product after trimming the excess veneer. At this point it would be ready to do any cutting to final size and drilling any needed holes.

It needs to sit for 24hrs before doing any finishing. I will try that next to see if I can match the existing finish.

John

Very interesting - thanks for detailing your process.
How did you trim the excess veneer ?

I have never really had good luck with the iron on veneer. I use very thin paper-backed veneer with contact cement. I typically reveneer an entire panel, or if it will be noticeable, redo a facing panel as well, so they will properly match. This of course involved stripping the entire cabinet. Maybe it's overkill, but by the time you are into that level of woodworking and preparation, you just may as well take it all the way.

Banderson-to trim veneer, I pretty much use whatever is sharp. I keep an Exacto knife and a variety of other razor blade tools, as well as a double edged razor blade like you find in the old safety razors-they are deadly sharp, and perfect for those tight corners. I also sand down the edges when I am done trimming. There are tools on the market that are also made for just such jobs as well, although they are really only good for straight edges.

Banderson, I used a utility knife. I did pick up a band trimmer, but it doesn't work well across the grain. Since I'll be working with the panel later, the trimming doesn't need to be precise. But, the utility knife turned out to be surprisingly precise.

Leadike, are you talking about the iron on veneer that already has the adhesive applied or the type of product that I used? I find that this HEATLock works really well. It's thermoset so heat doesn't help if you try to remove it later.

John

I decided to try using the method of wiping on orange shellac with a cloth to seal the wood and fill the grain. Photo one shows the materials. The shellac was cut with ethanol.

The shellac was wiped on trying to wipe most off of the surface. It was then sanded down to the surface. Several coats were applied. The result is in the second photo.

I then used Mohawk Utra Classic Toner, Brown Mahogany, aerosol lacquer to finish the board. The last photo compares the color of finished sample to the cabinet. I will be making a front panel to mount the bezel and I would like the panel to match the rest of the cabinet as closely as possible.

Being a bit red/green color blind I'm not sure how well I've done that.

I'm a bit confused about the cabinet. It's supposed to be Mahogany. The interior surfaces, even the hidden ones, are definately a Mahogany veneer that looks like modern Mahogany. The sides of the cabinet match that. The inside surfaces of the doors match it also. However, the front of the doors appear to be almost a different wood. I'd suspect that they put the wrong side out, but all of the other panels that are veneered have mahogany on both sides.

John

Nice job - that's a really good color match. Maybe just a tad more brown and less red, but I wouldn't worry about it especially if it's on a separate panel.

I've used Behlen water-base grain filler a few times. It's messy and there's a lot of rubbing and sanding, but the results are excellent - a glass-like surface.

How did the shellac work out as grain filler ? I've been meaning to try it out for a while since it seems less messy.

Maybe that odd veneer is from a different batch - or maybe it is a different species. That's one advantage of toner lacquer - it's easy to mix species and get the same color.

It takes more coats than I'd prefer. I had cut mine pretty thin for another project. It dries fast though. If you're refinishing a project the shellac is supposed to stick to almost anything, even urethane. I've not tried that.

John

Jj ecc-82
 

Has anyone had experience with J&J tubes? I noticed that the horizontal on my Sylvania was starting to drift out of alignment so I decided to check the tubes in that section. When I plugged the JJ ECC-82 into my tube tester one set of filaments lit up like a light bulb briefly. The other side was fine. I thought I made a mistake in the settings, but I doubled checked and also checked the voltage at the socket and everything was fine. It would also make sense that the problem I was having was due to this tube.

http://www.jj-electronic.com/pdf/ECC%2082.pdf They're made in the Slovak Republic.

They look really well made, but I'm leary of getting more as replacements.

John

That's just a 12AU7 isn't it ? I can send you a few if you need some.