Question about Akai PT4298HD Rear Projection Television

1 Answer

Akai PT4298HD Rear Projection

The picture is blurry. I tried "perfect focus" and it did not improve. I tried to use the convergence screen to adjust the focus, but it didn't have any effect. The convergence crosses were somewhat focused, but there were bigger blurry images of the crosses overlapping. It just does not focus the image properly.

Posted by on

  • nutrispot Feb 05, 2008

    I found this solution someone wrote and wondered if it would work for focusing the image better on my TV. Please let me know.



    "I have the same model and I had the red double the image on one side
    of the screen. So I thought that the convergence is messed up and I
    replaced the STK392-040 ($11 from Electronix.com) and worked like a
    charm"

×

1 Answer

  • Level 1:

    An expert who has achieved level 1.

    Hot-Shot:

    An expert who has answered 20 questions.

    Corporal:

    An expert that hasĀ over 10 points.

    Mayor:

    An expert whose answer gotĀ voted for 2 times.

  • Contributor
  • 53 Answers

Perfect Focus and the convergence screen are for convergence, not actual focus. Real focusing is done in a combination of two ways: electrostatic and optical. And to do it right you need a good test pattern, like the convergence pattern from the Digital Video Essentials DVD. At a bare minimum turn your contrast down to half (don't use "dynamic" mode, ever).

This is going to sound scary, cuz it terrified me at first but now I'm comfortable with it:

To focus electrostatically, the front panel under the speakers needs to come off. As in actually unscrewing some screws and opening up your tv. Do all of this without cats or toddlers in the room. There are three circuit boards on which the picture tubes are mounted, and each board has a focusing knob next to the words "red," "green," and "blue." Do not touch ANYTHING other than these knobs. Twist the focus back and forth until it is as focused as it will get. The lines on the convergence pattern will get fatter or skinnier. If they get fat in one direction and skinny in the other, find the best compromise. Do not focus the blue too perfectly, as perfectly focused blue lessens the amount of blue relative to the other colors, making whites look yellowish.

Next you really need to clean your lenses, they are filthy from dust and that's why the focusing is so bad. For this tv, you'll want all three panels on the front to come off. That's about twenty screws, both on the sides of the tv and the undersides of the panels. The middle panel that covers the speakers can rest on the floor by the front panel, but the screen panel needs a resting place. An ottoman, or a chair with a towel on it, makes a good place to rest the screen (parallel to the floor).

Each CRT has a set of focusing lenses, and these can be removed. Do one at a time. They come off from four screws each. FOUR SCREWS. Do NOT unscrew anything else, as just under the lenses is a cover for the CRT. Take this off and you risk coolant leak, leading to expensive electrical problems. Do not, repeat, NOT touch either the lenses or the mirror with your fingers. One scratch is bad. Scuff marks can destroy a picture. These lenses and mirror are easily damaged.

http://www.keohi.com/keohihdtv/learnabout/generaltips/screenoptics.html

There are some cleaning techniques there. I'd only bother cleaning the top and bottom of the lens assembly. Don't mess with the wingnut on the side, we'll handle that later.

Now, with your CRT lenses back on (wingnut facing towards the mirror), replace all of the panels and rescrew the screws. Next we do optical focusing. Again, this is where test patterns from a test pattern DVD come in handy. Regardless of what TV a person owns, a DVD like Digital Video Essentials is, well, essential.

This time we're taking a panel off the *back* of the TV. Scary, huh? Specifically, the bottom one (there are two big back panels). About fifteen screws, four of which are the same ones you do to get the front bottom panel off. Get all of the screws off, pull it back, and lift it out. Don't touch any of the electrical stuff. From here, if you are careful, you can reach up under the mirror and untighten the wingnuts on each CRT lens assembly. If you are using a test pattern, use a standard definition one here, makes the scanlines easier to see.

Here's what I do to focus each gun:
1) Put on a full screen of green, red, or blue, depending on which gun I'm focusing. DVE has just these patterns.
2) Untighten the wingnut, and start making minute adjustments.
3) What you want to see is *scanlines*, as clearly as possible. Make a tiny adjustment, get back around to the front of the tv, and see how well you can make out scanlines. An all-green screen should actually be a bunch of horizontal lines of green. If you can't make out these lines, you aren't focused.
4) If you don't seem to be making progress at all, switch to DVE's convergence pattern to make sure you haven't completely lost focus on that color. You want to start from good focus, and then fine tune very delicately.
5) You may find it hard to get blue-focus perfect. That's okay, really, as blue is a filler color. Green was very hard for me to see lines on, but it was a step up from not being able to see them at all.
6) You may find it necessary to go back and forth between electrostatic focusing and optical focusing adjustments to get them right. That's okay.
7) When it seems you've done the best you can, you're done. Put the back panel back on and rescrew all of the screws.

Now you need to adjust your convergence. You can use the user convergence menu, but it will only get you halfway there, because it only controls like nine or twelve points. What you want is to access the *service* convergence menu. With the tv on, press mute-1-8-3 on your remote (not pressing them all down, just in that sequence). You should switch to a secret built-in convergence screen.

I hate to tell you this, but the only way to save settings made in the service convergence screen that I know of is with a Samsung remote, not the Akai one. This tv is actually a Samsung after all, and the Akai remote is missing some buttons that the Samsung remote has. You can buy them off partstore.com, among other places. Here are what the buttons do:

7-allows you to control red convergence
8-allows you to control green convergence (what the screen defaults to)
9-allows you to control blue convergence
+100-turns red on or off
0-turns green on or off
pre-ch-turns blue on or off
circular direction buttons-moves the cursor to a new convergence point
channel up/down-moves the convergence up or down
volume up/down-moves the convergence left or right

ONLY ON THE SAMSUNG REMOTE:
add/erase-saves settings after blinking the screen and centering the cursor

If you can find a button on the Akai remote that does that, you won't need to buy a Samsung remote.

BTW, you'll want to do this service convergence on each scan rate. So one for 480p (from a progressive scan DVD player), once for 480i (s-video source or non-progressive DVD player), and once for HD (I use my HD DVD copy of DVE).

Posted on Mar 19, 2008

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

Picture is bowed at the top and bottom of the screen. The "Perfect Focus" option does not work to fix this. Is there a way to manualy adjust the picture


If the perfect focus isnt working its caused by failed convergence. You can get the convergence board from www.tvrepairworld.com its under the Samsung / Akai circuit boards.

Mar 30, 2011 | Akai PT5598HD 55" Rear Projection...

1 Answer

My akai pt4298hd is out of zoom and


akai is a samsung tv. you have a defective convergence board. suggest local service center. sorry

Nov 14, 2009 | Akai PT4298HD Rear Projection Television

1 Answer

Curved red image on 46" Akai rear projection TV


Yes! an idea that the flyback transformer is shot!


Please rate our help to keep the free service online

Aug 29, 2009 | Akai PT4298HD Rear Projection Television

1 Answer

Thin red line down the middle of screen


Enter muye 1 / 8 /3
it puts you into convergence mode and clears out all bad magic foces data.
then run perfect focus to save new data.

hope this helps
daniel

Jan 08, 2009 | Akai PT4298HD Rear Projection Television

2 Answers

PT4298HD Double image


BINGO thats exactly what i get paid to do same price 285.00

Nov 30, 2008 | Akai PT4298HD Rear Projection Television

1 Answer

Akai PT4298HD projection tv


convergence must be adj then saved then magic focus
if cannot be adj chips need to be replaced.

Sep 21, 2008 | Akai PT4298HD Rear Projection Television

1 Answer

Self focus


Go into the menu, then go down to "Function", then go to "Convergence". You can then go to the "Red" or "Blue" option and adjust each seperately. This will have to be done with your remote control. Just follow the on-screen instructions.....

 

Hope this helps you out!

Sep 30, 2007 | Akai PT4298HD Rear Projection Television

1 Answer

Green Shadowing Around Images On Akai PT4398HD


your convergence amp's are defective this can usually be repaired for a few bills. easy fix for a qualified repair person...john

Aug 31, 2007 | Akai PT4298HD Rear Projection Television

1 Answer

Convergence


Seems like you need to replace its convergence amplifier ICs (2 pcs). The convergence amplifiers are attached vertically to two heatsinks. When replacing these, remember to reapply thermal paste (white paste for better heat transfer from IC to heatsink). If you don't replace these, over time other components will be affected.

Aug 26, 2007 | Akai PT4298HD Rear Projection Television

Not finding what you are looking for?
Akai PT4298HD Rear Projection Television Logo

744 people viewed this question

Ask a Question

Usually answered in minutes!

Top Akai Projection Televisions Experts

Jaime Hernandez

Level 3 Expert

2267 Answers

seerads

Level 2 Expert

77 Answers

matt martin
matt martin

Level 3 Expert

1191 Answers

Are you an Akai Projection Television Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...