Sharp 32F540 - Bonded yoke?

[grossbard]

I picked up a Sharp 32F540 from a family member yesterday. It has excellent geometry for a flat CRT, problem is, the picture is rotated slightly. I opened it up to adjust the yoke but it appears to be a bonded yoke. It only appears to be bonded at the four corners. I'm debating on whether I should try to remove the epoxy so I can rotate the yoke (if this is even possible), or just live with it.

[Electronic M]

Have you checked the service menu to see if there is a setting for rotation correction?

[grossbard]

Originally Posted by Electronic M

Have you checked the service menu to see if there is a setting for rotation correction?

I did. No luck, unfortunately.

I noticed there's a pot on the Yoke. I wonder what it adjusts?

[David Bridge]

Originally Posted by grossbard

I picked up a Sharp 32F540 from a family member yesterday. It has excellent geometry for a flat CRT, problem is, the picture is rotated slightly. I opened it up to adjust the yoke but it appears to be a bonded yoke. It only appears to be bonded at the four corners. I'm debating on whether I should try to remove the epoxy so I can rotate the yoke (if this is even possible), or just live with it.

That CRT looks suspiciously like a Thomson (RCA) tube. It has a yoke clamp, so you can probably loosen it to rotate it just a touch. It also has the telltale "beam bender" magnet assembly that RCA Thomson used back in the day. Interesting that Sharp would buy their CRTs from Thompson at this time.

[grossbard]

Originally Posted by David Bridge

That CRT looks suspiciously like a Thomson (RCA) tube. It has a yoke clamp, so you can probably loosen it to rotate it just a touch. It also has the telltale "beam bender" magnet assembly that RCA Thomson used back in the day. Interesting that Sharp would buy their CRTs from Thompson at this time.

It's definitely a Thomson. It says "Thomson Mexico" on a label. The tv was made in 2004.

Each of those white pieces on each corner have some kind of epoxy on them, so I figured even if I loosened the clamp, I still wouldn't be able to rotate it?

[JohnCT]

Originally Posted by grossbard

It's definitely a Thomson. It says "Thomson Mexico" on a label. The tv was made in 2004.

Each of those white pieces on each corner have some kind of epoxy on them, so I figured even if I loosened the clamp, I still wouldn't be able to rotate it?

The early pre-yammed RCA yokes were located to the bell of the tube with epoxy. No way of getting one of those to move without destroying windings or the tube glass.

The one you have is held down by hot glue IIRC, so you can heat it and rotate it after loosening the clamp.

But, I would first try degaussing it with a manual degausser and also try rotating the cabinet 90 degrees. Large tubes are really picky when it comes to the earth's magnetic field.

Next I would try adapting the DC rotation scheme that a lot of TVs with large CRTs used. This was a coil that looked like a thin degaussing coil and it was controlled by a three position switch that would add a tiny bit of DC. Some used a positive voltage in one position, neg in the other, and nothing in the middle. Others (like Mitsubishi) used two switches, one for "intensity" and the other for polarity. This coil controlled the tilt and also purity (like in Mitsus) and was draped around the CRT in the yoke area.

I may have a coil for a 35" tube that will probably work if you're interested in it. If you are, I'll check the storage area.

John

[grossbard]

Here's some better pics of the yoke.

https://imgur.com/a/hgRuW3p

I appreciate the offer! but I'm starting to think I can live with the tilt. I don't want to possibly screw up the convergence or something else while trying to get the yoke loose.

[grossbard]

I moved the TV to where it's facing east - west instead of north south and it completely fixed the tilted image. If only everything were that easy!