Featured
Latest
Dare I say the word...
 
Share:
Notifications
Clear all

Forum 141

Dare I say the word, 'Plasma' or will I get black-balled!

11 Posts
9 Users
0 Likes
1,338 Views
Alastair
(@alastair)
Posts: 294
Reputable Member Registered
Topic starter
 

I know this is a 'Vintage Radio/TV site, but thought I would mention this out of interest...

During my normal 'dumpster-diving' visits to the local places, I found this 42" set that looked in good undamaged condition--Unusual, the places normally crack the screen or perloin the things as soon as they arrive....

Grabbed it anyway, thinking I should at least experiment with 21st Century rubbish, out of curiosity!

The set, a 'Hisense' (Never heard of it) had a L.G. PDP42V7 Chassis.

Examination showed that the main PSU caps a little distressed and a blown fuse on one of the other of the three main plasma driver boards.

I found a manual online and was completely shocked as to its contents over its 35 pages.

Basically it said, check this and that--If found faulty replace 'X' board complete, or replace three different boards at the same time.

No Schematic, no proper parts-list, just basic set-up for the few pre-sets it contains and how to remove and replace the panel and or the PCB's.
--Disgusting!

Doesn't Anyone repair to component level anymore....?

Anyway--I found that what they call--The YSUS board had a short-circuit MOSFET in the IPM, and blowing the Vs supply (185V) fuse....
--Whats an IPM?--I dunno--one of those 'Orrible 'STK' type modules under a huge heatsink. They call that item, 'Intellegent Power Management' device--Its actually just a collection of four mosfets and diodes with driver IC's--Nothing intellegent in there at all.....

So--out of curiosity I researched further and find this part is a common failure with this chassis--A VERY common chassis in 42" sets from Philips to Toshiba!--They all seem to use this L.G. chassis.

Outcome is, Ive managed to locate the devices for sale on ebay for only a tenner, so have ordered one. We shall see!

I dont think I'll be rescuing any more Modern Rubbish sets! :lol:

 
Posted : 13/03/2013 8:13 pm
Anonymous
(@anonymous)
Posts: 16832
Group Deactivated Account
 

Also the Plasma display itself has a running time that can make a projection tube look long lived.

Later models ran initially at lower drive and automatically increased drive to compensate for the ageing. OLED are also comparatively short lived displays.

I've not seen Hisense plasma, but a few years ago the LCDs common. Also the Hisense LCDs in the call centre part of the company I worked in proved that LCD get "burn in" too (perhaps the dye on LCD surface to add colour fades from backlight?)

 
Posted : 13/03/2013 8:43 pm
sideband
(@sideband)
Posts: 4214
Famed Member Moderator
 

Sounds like the same YSUS used in the older Philips Plasma's from 10 years ago. Same sort of manual with no real circuits. Just down to PCB replacements. Originally there was a repair facility in Eindhoven providing you sent the old PCB back they sent a 'reworked' PCB as a replacement.

We were told that under no circumstances were the YSUS PCB's to be repaired as the board is matched to the Plasma display which is why no parts were listed. I do know of engineers who have successfully changed these drivers though but also check for any bulging caps in the power supply as this can have a chain reaction effect.

Good luck. It will be interesting to see if you end up with a working TV.

I prefer PL81's and PY802's myself......! :=D

Rich

 
Posted : 13/03/2013 8:50 pm
ianj
 ianj
(@ianj)
Posts: 224
Estimable Member Registered
 

A mate of mine has a huge ( sharp, I think?) plasma set thats over 10 years old now, he now has a freeview box on it as its pre digital, and the picturetube is still working ok, though you can see the things worn, fast movements blur on it, but they dont care. The sound is very good on it, as it has twin forward facing speakers either side of the tube, which must be 50". Its on its own stand. I suppose its on borrowed time, as is my crt set, a Philips 100hz heavy lump lol

 
Posted : 13/03/2013 8:56 pm
Lloyd
(@lloyd)
Posts: 1897
Prominent Member Registered
 

I saved a plasma set from a bin last year, I also documented it here :)

The power board wasn't kicking out the -185v, some 4 legged thing had gone pop, I did try changing it, but it blew again. I ended up buying a new power pcb from eBay. The set is now working well, and the screen looks like its got loads of life left in it, just a tiny channel ident burnt into the top left corner, only noticeable on plain coloured pictures.

 
Posted : 13/03/2013 9:12 pm
Alastair
(@alastair)
Posts: 294
Reputable Member Registered
Topic starter
 

From my limited research, it appears that the IPM has two 15V supplies.

One is for the 'high-side' drive of a set of MOSFETS and the other, the 'low-side'
The High-Side is a floating supply derived via DC/DC Converter from the 5V supply.

The YSUS board in the PDP42V7 has two main rails to it. The 185 'Vs' supply and the 5V (at 8A) Both 15V supplies and an additional 5V supply is derived from the 'main' 5V rail via a transformer from the 5V from PSU board.

The Transformer and the three voltage-regs are on the YSUS board in a fairly 'warm' place, the caps being of those nasty 'surface-mount' leccy-lictics, not even having any 'temp-rating'

There are two more (so far Ive found anyway) supplies that are involved with the 'Set-Up' and 'Set-Down' adjustments for the plasma panel, but these appear to be derived from the 185V supply.

A 'chain-reaction' does seem to occur where the high-side 15V rail to the IPM's (Theres two per set, one in YSUS and the other on the ZSUS board, goes low causing excess heating of the 'output' MOSFETS in the IPM's.
--Indeed, the appearance of the PCB board indicates that the IPM has been getting fairly warm despite its huge heatsink, the board having a slight darkened appearance where the IPM is positioned.

I'm guessing the 15V rails slowly decrease, and get ripple on them as the caps in their circuits dry up causing the IPM to overheat and eventually self-destruct, as there's too low a voltage to drive 'em hard on.

I plan to replace most if not all the small caps relating to all these low-volt supplies and the 7 or 8 10uF 350V caps relating to the 'set-up' and 'set-dow'n supplies too. (Apparently, these supplies are pretty important to the picture brightness/ghosting/sparklies/pixelation effects--I dunno, I'm just gonna change 'em!--There's bags of 'em on ebay and they are cheap!) :thumbr:

--Seeing the small supplies are all derived from the 5V rail, I can run the board from an old computer PSU before getting it anywhere near the set, to confirm all the proper voltages are present first, then check out the set PSU for any issues relating to the caps etc....

The main 'Vs' supply is decoupled by 5 150uF caps on both the YSUS and ZSUS and a whole load of 1uF film-caps too. These appear to be OK....

The IPM,is a 'YPPD-J014C' module is coming from China so probably be a week or two before I get anywhere with it. Also been researching repair of the actual IPM--like the Russians do, by fitting replacement MOSFETS in place of the 'die' chip components inside the IPM's.... :w00t:

 
Posted : 13/03/2013 10:19 pm
Red_to_Black
(@red_to_black)
Posts: 1748
Prominent Member Banned
 

Hi Al,

This chassis has a three panel kit available, which at one time was a reasonable price (unfortunately not so reasonable now :| ), be very careful though there are a few different versions of this kit, and not all are suitable for a given version/make of set/plasma panel.

http://www.chsinteractive.co.uk/electri ... yh036d.htm

Some times one of the Buffers also fail, which can take out the repaired Y-sus, or vice versa :| , this is the problem with plasma sets, one panel can take out others, only you won't know until you replace/repair the obviously faulty one.
Even worse is when you replace a panel, and another faulty panel damages the new one but in a different way.

As a side note, I always thought 'IPM' stood for Integrated Power Mosfet , but could be wrong on this. ;)

 
Posted : 13/03/2013 11:55 pm
Red_to_Black
(@red_to_black)
Posts: 1748
Prominent Member Banned
 

Re:

As a side note, I always thought 'IPM' stood for Integrated Power Mosfet , but could be wrong on this.

I just looked at the Philips variant manual of this chassis, and you are correct, they do indeed call it an intelligent power module. :=D , oh! well :O

I forgot to mention in the previous post wrt the kit, all 3 panels were supposed to be replaced together.
I can remember getting this kit for about £60 + Vat trade at one time (very reasonable), then for some reason the price rocketed and made a lot of these older plasma sets BER, which was a shame.

 
Posted : 14/03/2013 12:35 am
malcscott
(@malcscott)
Posts: 1566
Prominent Member Registered
 

I have a Techwood plasma tv which uses the LG 42v5 display. It is well over 10 years old and still gives a brilliant picture. I aquired this set about 8 years ago with a faulty psu. Once sorted i set about drilling lots more ventilation holes in the rear cover. Never been any problem since, Malc.

 
Posted : 14/03/2013 12:57 am
mark pirate
(@mark-pirate)
Posts: 497
Honorable Member Registered
 

These modern sets are always worth a go, I bought a 42" Samsung plasma for £15 at my local boot sale, on powering it up.... nothing, no standby light, totally dead.
Googling the model No came up with an ebay link to a 'set dead' repair kit consisting of four caps.
So off came the back, all fuses intact, but a close look at the power board revealed a domed cap, so out came the board for a closer look, there was no other obvious dodgy caps, so I replaced the cap and replaced the board.
On powering up the set works perfectly :D
I bought a wall bracket and fitted it to the wall, it is working great, but I run the sound through my hi-fi, as the pathetic internal speakers are pants.

I bet the original owner would be gutted to know that a 50p component was the only fault!

 
Posted : 14/03/2013 8:19 am
freya
(@freya)
Posts: 1312
Prominent Member Registered
 

I have to chuckle with all these admissions of plasma`s being harvested from boot sales and the like, i too got my TH37PE30 37 inch viera from a tv shop that was arson attacked in 2004
The set itself was just covered in black smeech, which the owner cleaned off the front and back with cif or similar. This in itself was ok but he turned it on straight away without realising he had inadvertantly sprayed some through the back vents onto the YSUS board.
As it was a brand new display model at the time he was not best pleased but insured anyway, the set found its way to me and i repaired the blown mosfets on the YSUS board plus had to replace a driver board that had blown a hole in the driver chip.

Its used every day as the family viewing set.

Stephen

 
Posted : 14/03/2013 6:24 pm
Share: