Question about Akai Projection Televisions

6 Answers

I need to adjust the voltage regulator in an attempt to minimize the "red spotting" on the screen in very dark areas. I was told this is the first step prior to replacing the video card. How do I go about this adjustment?

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  • dw_sherer Oct 13, 2008

    I asked for the information, not a lecture from someone who apparently doesn't have it.
    Can someone please tell me where to locate the potentiometer on the back of the set? I'll take it from there.

  • dw_sherer Oct 13, 2008

    the last solution was for a homemade tv tuner, not the pwr supply of the akai pdp4873m plasma tv. if this is all the help i'm going to get, i think i'm going to have to ask for my money back. again, i need to know the location of the pwr supply potentiometer for the akai pdp4873m plasma tv.

  • dw_sherer Oct 14, 2008

    thanks for pointing out what i already knew. now please tell me where that circuit board is located and which trimmer it is. generic and vague answers only serve to prolong this ordeal and tend to make the so-called experts appear as though they know less than i do. by the way, you're speaking to a degreed electronics engineer with 30+ yrs experience,so don't blow smoke.

  • dw_sherer Oct 14, 2008

    this is a plasma tv, there is no convergence to correct. it has red speckles in dark areas of low contrast.

  • dw_sherer Oct 14, 2008

    well, this has been interesting. i was able to solve the problem by increasing the brightness and removing the adaptive luma control. the picture is a little softer and much cleaner in color. this whole ordeal has left me wondering why anyone connected to this sight calls themselves an expert or a guru. i may replace this tv, but not in the near future. i will, however, be asking for my money back from the group. you see, the sight advertises tech support, instructions and repair service....none of which were offered, only a lot of misdirection and admitted incompetence.

  • dw_sherer Oct 14, 2008

    barneyluc had the only helpful advice and information. this guy knows his stuff. i will still be leaving for good as this is more of a forum than a real tech info service. you guys have fun....i'm outa here!

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6 Answers

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Hello,

thank you for using fixya.
I know that all experts here are trying hard to resolve the issues, however we only have limited ideas to diagnose you stuff because is not personally troubleshoot.

melnavz

Posted on Oct 14, 2008

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Hello, You need to order the manual from servicemanuals.net ,sir. They do not have your sets service manual (I tried already)but claim they can locate it for you in 24 hrs. I looked for the schematic on the 5 service manual download sites I know and none had your unit. The closest I came was a pdp4216m on www.service-manual.net. They want $12 US for that schematic....possibly they also can get it for you.
I am an electronic technician...worked on consumer electronics for 20 + years. I loved your responses to some of the other solutions!!! Very entertaining!!! Good luck to you!!

barneyluc

Posted on Oct 14, 2008

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Its the problem either of convergence settings or the convergence IC on the main power supply board is gone faulty.

for settings click this link
http://www.somelifeblog.com/2007/06/sony-projection-tv-red-line-repair.html

for IC click this link
http://home.earthlink.net/~oleg.filippov/ConvergenceFix.htm

thanks.

hope this helps....

Posted on Oct 14, 2008

  • ready2helpu Oct 14, 2008

    For slight tweaks, the following is not necessary. However, if someone
    turned all the internal controls, if you are making significant changes
    that affect G2 (screen), or you are setting up a new or replacement CRT for
    the first time, then following the procedure below is desirable to achieve
    best performance and maximize life of the CRT.

    The typical user controls - brightness and contrast can, of course, be set
    arbitrarily, depending on video content and ambient lighting conditions.

    Set the user brightness and contrast controls in the middle for the following
    adjustments and let the monitor warm up for 20 minutes or so.

    (From: Jeroen Stessen (Jeroen.Stessen@ehv.ce.philips.com)).

    Now the screen control, that's another matter. It sets the voltage
    on the second grid of the electron guns, typically between +500 and
    +1000 V. You will want to use a well-isolated screwdriver for that
    if it is a naked potentiometer. In the old days there used to be 3
    separate potentiometers for 3 G2s, now there is generally only one.
    Its purpose is to set the cutoff voltage for the guns, i.e. the
    voltage between K and G1 at which the beam is just off. The higher
    you set the VG2, the higher VK - VG1 must be to cut off the beam.

    If you set VG2 too low then your picture will be dark. You can
    compensate for that with the brightness control, which in effect will
    lower the VKs. A disadvantage is that you will not get optimum
    sharpness and peak brightness from your picture tube.

    If you set VG2 too high then your picture will be bright. You can
    compensate for that with the brightness control, which in effect will
    raise the VKs. You might even get retrace lines which can usually
    not be made to disappear with the brightness control. Another
    disadvantage is that you will not get optimum LIFETIME from your
    picture tube. With a too high cutoff voltage the cathode (electron
    emitting surface) will wear out too soon.

    You will need to see the picture tube specifications (or possibly
    the service manual for the monitor --- sam) in order to find the correct
    setting for the cutoff voltage. This is measured as VK - VG1 (for each
    channel RGB) and is typically 130-160 V max. There will be spread between
    the 3 channels, typically the highest of the 3 measured values will be set
    against the upper limit.

    The usual adjustment procedure is as follows:

    * Use any low-level adjustments to set a black picture with all 3
    cathode voltages at the specified level (e.g. 130 V) above
    the VG1 voltage (may be 0 V or 12 V or 20 V ?). (These are typically
    called RGB brightness, bias, or background level and are often on the
    little board on the neck of the CRT but not always --- sam).

    * Adjust VG2 (screen) until one colour just starts too light up,
    turn it back down until the screen is just black again.

    * Now adjust 2 of the 3 low-level black controls until the
    other 2 colours just light up, and then back to black again.

    * Select a white picture and use 2 low-level white (RGB drive or gain, also
    generally on the neck board --- sam) controls to set the proper colour
    temperature for white to your own taste.

    * Check your black calibration again, may have to iterate a bit.

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U have to set it by the tunning a trimmer from the ckt bord 

Posted on Oct 13, 2008

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Please go to the following link http://www.vernk.com/images/TvTransmitter/ATV_Tuner_InsideView.jpg

This will give you the pictorial representation of where exactly the voltage regulator is located. Hope this will be of some help to you.

Thanks

Posted on Oct 13, 2008

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  • Akai Master
  • 61,289 Answers

You are going to need a factory repair manual before you even should attempt this kind of repair, you say you heard this from whom? if you get it wrong the TV voltage adjustment can burn out other circuits, leave it to the pro's to deal with an issue such as this.

Posted on Oct 13, 2008

  • yadayada
    yadayada Oct 13, 2008

    I would ask for for a refund, we don't want to be a party to you causing more damage to the set, you need a manual, do you have one? we do not have any manuals, we are just private individuals working at home, most of our knowledge is of a general nature based on experience in the field. Thanks for choosing FixYa.

  • yadayada
    yadayada Oct 14, 2008

    You need to replace the TV, get a LCD they are much more reliable than the Plasma.

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1 Answer

Red Lines through picture when screen is dark, back ground has a red tint. On my 48 "Sony Rear Projection" TV


You can try adjusting the Red color output. (Very touchy adjustment)

If you take off the front cover/speaker cover, there should be a access panel. Behind that, there should be a small square black box with 6 screws on it. This is the focus block. (At least this is where most of them are located)

It sounds more like you may need less red in the mix. There is a screw for each color. R, G, and B. Do not mess with the focus screws, just the ones labeled 'SCREEN.'

Go to an unused input where the screen should be dark. Barely turn the red down in a dark room so that the red spot is at the same level as the Blue and Green.

Use an insulated screwdriver and DO NOT TOUCH the focus block and ESPECIALLY NOT the back of it.
Very HIGH VOLTAGE. I found that out the hard way.

Do not turn any of these up too high or damage may occur and the TV may detect a short and shut off.

I have found that if the three colors are adjusted in a dark room to where the 3 color spots (R/G/B) are just barely visible on the screen at equal levels, there is a pretty good color balance.

I hope this helps! Just be careful.

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1 Answer

Picture is very blue most times.This is a light blue, but makes viewing difficult. Also before this issue came about, you could see a faint set of arcing lines running across screen especially when screen...


You can try adjusting the Blue color output. (Very touchy and dangerous adjustment)

If you take off the front cover/speaker cover, there should be a access panel. Behind that, there should be a small rectangular black box with 6 screws on it. This is the focus block. (At least this is where most of them are located) If there is no front panel, It may be located on or near the flyback (High Voltage) transformer on your model accessible from the back instead.

It sounds like you may need less Blue in the mix. There is a screw for each color. R, G, and B. Do not mess with the focus screws, just the ones labeled 'SCREEN.' They may have silicone over them to prevent them from moving. If so, you will need to remove it and put more on when adjustment is complete.

Go to an unused input where the screen should be dark. Barely turn the blue down in a dark room so that the Blue spot is at the same level as the Red and Green.

Use an insulated screwdriver and DO NOT TOUCH the focus block and ESPECIALLY NOT the back of it.
Very HIGH VOLTAGE. I found that out the hard way.

Do not turn any of these up too high or damage may occur to the tubes. If you turn them up too much, the TV may detect a short and shut off. this is a normal fail safe. These only need VERY slight adjustments.

I have found that if the three colors are adjusted in a dark room to where the 3 color spots (R/G/B) are just barely visible on the screen at equal levels, there is a pretty good color balance.

I hope this helps! Just be careful. Once again - LETHAL HIGH VOLTAGES ARE PRESENT WHEN UNIT IS ON!!!!!!

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1 Answer

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