Scrunched screen on samsung 50" plasma

[bootlegger17]

Recently I was given a dead Samsung 50" plasma.
It would not boot - blinking light and clicking PSU (relay)
My first searches led me to replace the input board controller. This did not fix the issue. A bit more searching and a few replacement parts later, I discovered it was a faulty X board - this has now been replaced and the TV now boots up.
I got the 'No signal' box on the screen so thought it was working and took it to my living room and plugged it all in, only to find that the screen appears scrunched up.
What I mean by this is that the full correct display is only shown on the first 3/4s of the screen - the last 1/4 is completely blank. Its not like the last quarter is damaged and is missing the last quarter of the display - the full display is there, just scrunched up to the first 3/4s of the full display.
Its almost like a controller board doesnt know that I am on a 50" display, but it thinks I am on a 38" maybe? I also notice sparkles down the very left hand side, fading out to the right hand side (about center of screen before they fade completely).
I am Puzzled


I have checked the Voltages (vs/Va?) on main power board and these are in tolerance, but am unsure of the vscan/ve voltages as I am unsure how to check them on the Y sustain board. (i believe this may fix the sparkles once in tolerance)

So the two boards that have been replaced are the X board and the Input source controller board. The Y sustain, power board, and tcon are the original boards so I dont suspect these board.

I have performed a factory reset on the TV but this made no difference.

Any one got any ideas how and why this should be?

I unfortunately dont have the original input source board as I damaged this BER (trying to reflow as I thought I had nothing to lose as I had a new one anyway). I suspect this board is this issue, but I made sure it was the exact same model code/ part code etc when purchased - inspection of the board doesnt show any jumpers or things I can adjust on it.

Any help appreciated.
Jason

[tom66]

Re: Scrunched screen on samsung 50" plasma

If you used a main board from a 42" then it would have a 1024x768 resolution whereas most 50" 720p plasma panels are ~1366x768. Hence the scrunched look - the panel is only driven with a 1024x768 image.

So you would need to use a 50" board.

--OR--

You can try accessing the service menu: from standby press Info Menu Mute Power on a European model, Mute 1 8 2 Power on a US model. Then access panel option and try to switch it to 50". Not always possible on Samsung panels.

--OR--

You can try to transfer the EEPROMs from the 50" board to the 42" board which would copy its personality across.

[bootlegger17]

Re: Scrunched screen on samsung 50" plasma

interestingly i just saw a sticky thread about accessing service menus and am just having a look in there now.
When i do an mstar pattern test, it only occupies the 3/4 screen, but when i do the Logic test patterns, it fills the full screen. This gives me some confidence that I may be able to fix it in the service menu some how. I will look for things related to what you mention. I am a bit nervous about the moving eprom option incase I kill another board, but it may be my last option - thanks for the detail so far. Regards Jason

[bootlegger17]

Re: Scrunched screen on samsung 50" plasma

I see in the SUB section about the OSD resolution at 1024*768 but this does not appear adjustable. I also see in the PDP section Panel Inch 50HD. bit of a mismatch?

[tom66]

Re: Scrunched screen on samsung 50" plasma

can you change Panel Inch?

[bootlegger17]

Re: Scrunched screen on samsung 50" plasma

There are several options which I think are essential to change, but there appears to be no way of saving the changes. No obvious save option.
There is a PDP Type which is set to PB43?42sd, which can alter to PB45?50sd and another code at PB430 which can alter to PB450, but cant seem to save the changes, so after power off and on, it goes back to previous settings. It doesnt appear to take immediate effect after alteration either, so I guess it will only work after a power recycle if the settings could be changed. I got stuck in the service mode at one point also, no matter how much i recycled the power - I think pressing the mute button does a save effect before pressing the power button , but I am not sure, but if so, I tried that after altering the PB values from 42 to 50, but it still wouldnt retain the settings. I also upgraded the firmware but it appears its a generic firmware for many models. Lastly I have reset NVR and EPROM settings, but again, no difference.

[bootlegger17]

Re: Scrunched screen on samsung 50" plasma

Tom66 - you are a god damn genius man!

I replaced the eproms around and now it operates in full screen.

Got some diags to do yet , and want to get the settings written down for the future just in case, but so far so good.

I owe you a pint!

Jason

[tom66]

Re: Scrunched screen on samsung 50" plasma

Nice to hear, for future ref, what chips did you swap?

[bootlegger17]

Re: Scrunched screen on samsung 50" plasma

it was the eprom on the underside of the board (AT ML H906 off broken board to replace the AT ML H912 on the working board) - labelled as IC3001 on the board

[bootlegger17]

Re: Scrunched screen on samsung 50" plasma

Dunno if it will be useful for anyone else, but heres my settings from my service menu on my working telly.

[bootlegger17]

Re: Scrunched screen on samsung 50" plasma

Lastly, it might help if I give you some model details;

MODEL CODE : PS50B451B2WXXU
Version : BF04