Plasma power failure Hitachi 42pd5200eh.

[Portishead]

So guys, budm?

I have a plasma tv currently not working. Some weeks ago it just wouldn't turn on one morning. Pressing the mechanical power button, it sounds like the unit is going to start, makes several usual internal clicks then another click a couple seconds later and nothing.Almost like it's gone into standby. However, the green power light stays lit on the front throughout . It does not go red as standby.
Any thoughts?
I have come across this as a possibility but again, I do not know.

http://pages.ebay.com/link/?nav=item...695662&alt=web

Here is the board: (power board anyway) MPF7409

[Portishead]

Re: Plasma power failure Hitachi 42pd5200eh.

Perhaps someone could advise me how to test these on my board firstly?

http://pages.ebay.com/link/?nav=item...560625&alt=web

[Alastair E]

Re: Plasma power failure Hitachi 42pd5200eh.

TBH--I wouldnt spend a single penny on that set!

Those Fujitsu/Hitachi PDP age terribly and give a bloody awful dingy picture covered in mal-discharge....

They gotta be THE Worst Plasma Ever made for lifespan and picture-quality, not withstanding their original humungous cost and lack of DTV!.

[ReeceyBurger123]

Re: Plasma power failure Hitachi 42pd5200eh.

Agree with Ali the only good thing about them is that the Sustain drivers are probably the best ever, rarely fail. But the screens wear out fast as Vs is only 60v or so which isnt enough to prime the panel enough.

[Alastair E]

Re: Plasma power failure Hitachi 42pd5200eh.

Dunno just Why Hitachi/Fujitsu designed the PDP for such a low discharge voltage--Most makers use three times that voltage, and more....

[Portishead]

Re: Plasma power failure Hitachi 42pd5200eh.

I love the picture it gives. It's excellent and the sound is amazing for 8yrs old.
So, I'd like to fix it. If I can fix it for £10 then good on me. It's all to easy now to throw everything away in the ground because nobody is interested in repairing things because labour charges are astronomical . It's Just the way it is. You'd have to spends hundreds to get close to what this plasma puts out. I've just bought a new Sony led lcd bravia what ever . It's ok, but the picture is dreadfully dark, And if I move slightly away from sitting infront of it the picture goes. And the sound is disgusting quite frankly. I never did like these weird blury lcd led pictures. They just look odd.
So, I'll stick.with my bright clear plasma. 8 years old and a.minor repair isn't bad going.
If I can fix it!
But thanks for your kind help.

[tom66]

Re: Plasma power failure Hitachi 42pd5200eh.

Agree with Ali the only good thing about them is that the Sustain drivers are probably the best ever, rarely fail. But the screens wear out fast as Vs is only 60v or so which isnt enough to prime the panel enough.

Vs is 85V usually on FJH (FujitsuHitachi) PDPs. It's actually a split +/-85V supply giving a Vs of around 170V. Pretty typical for the low luminuous efficiency panels used in earlier models.

Later Hitachi sets used a split Vs of +/-95V to +/-105V, giving a Vs of around 190V to 210V.

Dunno just Why Hitachi/Fujitsu designed the PDP for such a low discharge voltage--Most makers use three times that voltage, and more....

The reason the Vs is lower is because the sustain boards use TERES design. So instead of one board outputting Vs and the other 0V (or 0V and Vs) they output +Vs and -Vs. This produces the same voltage across the panel, but each half of the sustain board need only withstand half the operating voltage, reducing the cost of the board. Va is still single-ended on the address buffers, hence why it is in the typical 50-60V range.

It essentially meant that they could use MOSFETs (with lower breakdown voltage of c.a. 120V) instead of IGBTs (~330V rated); MOSFETs have lower losses and cost less per unit. However, it increased the expense in other areas, such as the power supply, which now needed two separately regulated supplies, and increased other complexities on the sustain boards. Since the supplies came off the same transformer they couldn't use the Vs supply to power the other loads for example the Vscan and Vsch voltages, as loading just Vs and not the -Vs would cause a supply imbalance, causing picture discharge issues. (Some later Panasonic plasmas, 2012 or so, used a separate power supply for SC and SS sides, and on some models the potentiometers aren't well matched, causing a purple discharge to appear on one half of the display.)

Hitachi did stick with the design until their exit from the plasma market, so I can only presume they had figured out the design challenges in this area. But with the falling cost of IGBTs and the higher efficiency of the panels overall there was probably no more need to use a TERES architecture, hence why NEC & Pioneer did not adopt this when they purchased Hitachi's PDP unit.

The gas pressure of a plasma panel defines the minimum operating voltage. The older panels used a low-efficiency design which had low gas pressure. My dad's 11 year old NEC plasma which sucks ~550W (50" screen, 720p resolution) uses a Vs of just 160V or equivalently +/-80V (though it uses an NEC/Pioneer panel so it does not have TERES configuration.)

As technology improved manufacturers were able to increase gas pressure, and with increased gas pressure came increased sustain voltages and efficiency - some Samsung panels in 2014 were using a Vs of 227V! (F8500 being an example with its very high light output.)

[Portishead]

Re: Plasma power failure Hitachi 42pd5200eh.

Bump

[ReeceyBurger123]

Re: Plasma power failure Hitachi 42pd5200eh.

Have you checked if you get Vsus voltage ?

[Portishead]

Re: Plasma power failure Hitachi 42pd5200eh.

Would you mind telling me how to check? I have a multi meter
.

[tom66]

Re: Plasma power failure Hitachi 42pd5200eh.

Check the pins marked Vs on the power supply.

I have a feeling I have met this fault before on other LG-panel Hitachi sets (with a strange combo of Hitachi power supply, Vestel main & tuner board, and LG plasma display panel)

Some thru hole resistors on the PSU had failed open (as part of the inrush limiting circuit), causing the TV to stay stuck in standby. It would not attempt to click the inrush relay on, because the relay supply was provided by a circuit after those resistors, which wasn't being powered.

See if you can locate two or three white ceramic box resistors and test them...

[Portishead]

Re: Plasma power failure Hitachi 42pd5200eh.

What should I check for on the pins? It's marked vs all over the place. And also on other boards.
There are at least 5 white box ceramic resisters shown on my pic above. How should I test them? What am I looking for?

[tom66]

Re: Plasma power failure Hitachi 42pd5200eh.

The particular resistors are in the top left of the power board. Check the resistance across each matches, or is close to what is printed on the resistor.

Vs can be tested on any pin marked Vs.

[Portishead]

Re: Plasma power failure Hitachi 42pd5200eh.

Ok. I've set the meter on 200? They both read 10.3
The resisters are marked 10. OK?

So, assuming the set has to be plugged in live, I see a couple of pins as per picture here. Are these the test points for vs? Am I looking for ac or dc on my meter?

[vinceroger69]

Re: Plasma power failure Hitachi 42pd5200eh.

The restistors toms onabout are the oblong white cement ones just too the left of the ones you have checked theres a few on the psu check them all just to rule them out.

[Portishead]

Re: Plasma power failure Hitachi 42pd5200eh.

Sorry, yes I have tested those two in top left. 10ohm ones. They appear ok

[vinceroger69]

Re: Plasma power failure Hitachi 42pd5200eh.

The restistors toms onabout are the oblong white cement ones just too the left of the ones you have checked theres a few on the psu check them all just to rule them out.

sorry yes you tested the rite ones im not sure about the test points you mention though im sure someone will advise you.

[jetadm123]

Re: Plasma power failure Hitachi 42pd5200eh.

You can try testing the two K2843 mosfets (mounted on heatsink) for shorts. They tend to go short on this power supply.

[Portishead]

Re: Plasma power failure Hitachi 42pd5200eh.

You can try testing the two K2843 mosfets (mounted on heatsink) for shorts. They tend to go short on this power supply.

Just run it by me again how to test those again. I have located them.

[jetadm123]

Re: Plasma power failure Hitachi 42pd5200eh.

1) download datasheet for 2SK2843 mosfet

2) set your meter to low ohms scale (something like 200 ohms)

3) with power off, measure across:

Gate--->Drain

Drain--->Source

Source-->Gate

Low resistance will indicate a short