Hisense Plasma PDP4235EU

[s_henya]

Hey guys,

my freind gave me this plasma for my birthday, he had no use of it,

the problem is that frequently the top of the screen is black

(about the 1/3 of the screen, upper side.)

i'll try to catch this online, and take some pictures.

i have no expirience in plasma TV repair.

please guide me what to look for.

i opened it up, and found no visual faults,
(bad caps or burn marks)

[tom66]

Re: Hisense Plasma PDP4235EU

Can we see a picture of this sticker -- we can look up panel model etc. and get a service manual if one is available.

[s_henya]

Re: Hisense Plasma PDP4235EU

hey tom,

thanks for responding,

i've added a picture of the sticker as you asked :-)

if more pictures are needed,

i'll be more than happy to attach them too.

[tom66]

Re: Hisense Plasma PDP4235EU

Very rare panel. Appears to be 480p, but modern, I guess for the budget market.

I don't have a manual for this panel unfortunately.

However tests are still possible.

You will need at minimum a digital multimeter. Ideally, you would also have an oscilloscope. Do you have these pieces?

[s_henya]

Re: Hisense Plasma PDP4235EU

i have a multimeter but dont have a scope
i fixed a couple of LCD TV snd monitors
but this is my first plasma project.

because it wont happen all the time could it be
a cold soldering joint or loos connection of the flat cables

i also noticed that part of the screen has some
flickering dots, hope you know what i mean.

on which pcb should i focus, im gussing that the psu is ok

[tom66]

Re: Hisense Plasma PDP4235EU

When the fault occurs, can you show me a photo, with it playing a video? My guess would be somewhere on the Y-buffer, left hand board with 6 chips on it going to the plasma panel.

[s_henya]

Re: Hisense Plasma PDP4235EU

will do i will let it run and take a few pictures

i feel like an idiot but could you guide me
which pcd is the y buffer?

[tom66]

Re: Hisense Plasma PDP4235EU

This photo
https://www.badcaps.net/forum/attach...9&d=1368727494

Left hand board with 6 chips on it going to the plasma panel. Runs along the left hand side. Drives the rows of the plasma panel.

[s_henya]

Re: Hisense Plasma PDP4235EU

good that was my guess too!
is there any point in
try reseating the flat cables in the sockets
after spraying some contact cleaner?

(works with lvds connector in lcd monitor problems)

[tom66]

Re: Hisense Plasma PDP4235EU

I wouldn't think so at the moment, first wait for the problem to occur so we know what the fault is. Be very careful with contact cleaner. Plasma uses almost 200V on those outputs, so the contact cleaner can conduct if it is only suitable for low voltage circuits.

[s_henya]

Re: Hisense Plasma PDP4235EU

ok, thanks for the warning,
ill wait and take a few pictures first.

[s_henya]

Re: Hisense Plasma PDP4235EU

what do you think?

1/3 of the upper screen is black

[tom66]

Re: Hisense Plasma PDP4235EU

OK, so in a dark room, is the failed portion glowing slightly? A plasma panel will glow slightly if it is being energised.

[s_henya]

Re: Hisense Plasma PDP4235EU

it lookes just like an lcd with no backlight,

you can see the picture but there is no light.

[tom66]

Re: Hisense Plasma PDP4235EU

OK, my suggestion would be the 2nd buffer IC from the top has failed on the Y-buffer, perhaps it is intermittent. Each IC chains the signal to the next. Look at the part # on it. They may be replaceable or you can get a whole new board.

[s_henya]

Re: Hisense Plasma PDP4235EU

ok should i google this sticker?

hope you can see the number of the IC in the picture.

any guess why does it happen randomly?

[tom66]

Re: Hisense Plasma PDP4235EU

Do you have freeze spray or a hairdryer available? I want to rule out nearby MLCC too. It's probably related to the heat produced by the ICs.

Here is the chip, $13 each, so see if a buffer board replacement will be cheaper (perhaps you can get it from another TV with cracked screen, but beware sometimes buffer is damaged by cracked screen.)

http://www.aliexpress.com/item/IC-CH...631122161.html

[s_henya]

Re: Hisense Plasma PDP4235EU

freez spary no, but a air compressor-> it blows prerry cool air,
hairdryer, and hot air rework yes.

tell me what to do, and i will let you know right away.

got an Infrared thermometer, capacitance & esr meter, digital multimeter.

[s_henya]

Re: Hisense Plasma PDP4235EU

thats odd, either my PEAK ESR70 is wrong because of in circuit testing,
or most of the smd caps shows more than 20 in ESR.

by the way couldn't find this pcb anywhere... :-(

[tom66]

Re: Hisense Plasma PDP4235EU

You can't use an ESR meter on those capacitors, they are too small. Anyway, their failure mode is typically leaky or short, which an ESR meter will not capture.

What you need to do is get a cardboard roll tube, like a toilet roll tube, and concentrate the heat on the 2nd chip from the top. See if you can get the picture to blank out much faster than it otherwise does. If heating the chip doesn't significantly increase the time, then move on to the nearby capacitors -- perhaps best to use hot air rework at a low temperature, no more than 100'C.