Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible?

[johnboy1313]

I found this one for sale locally, about an hour away. The owner claims that it powers up fine with sound and a full picture then shuts off and gives 7 blinks, which from what I can best tell means bad SD, SU, or SC. My lone personal experience with the 7 blinks was a bad SC board which gave no picture or sound whatsoever. From what I've read, if the SD or the SU was bad there'd be no picture at all unless the bad board was disconnected. In which case, there'd only be a half picture and then that means the panel is bad too. Is it even possible to get a good full picture with sound if any one of these three boards is bad?

The owner keeps telling me that he'll do me a favor and meet me halfway so I don't have to drive the full distance. My suspicion is that he is willing to do that because he doesn't want me to be able to plug it in.

Care to add your thoughts?

[tom66]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

SM: http://www.tgohome.com/ServiceManual...&Search=Submit

The owner keeps telling me that he'll do me a favor and meet me halfway so I don't have to drive the full distance. My suspicion is that he is willing to do that because he doesn't want me to be able to plug it in.

Yes, this is a possibility. I always bring a power cord and extension lead so I can plug in a TV, but I'm considering investing in an inverter so I can run a TV for a few minutes off a battery.

However, it is possible to get momentary 7 blinks. The A Board can be defective, leading to mis-diagnosis, as it warms up. Or 7 blink error only kicks in after SOS7 is high for >500ms (possibly more on older chassis) and in some cases this only happens after the first few sustain periods.

Also, 6 blinks can be caused by a drop in the energy recovery voltage, which can occur if the energy recovery circuit is not functioning properly. The panel will still work, but the TV will use much more power (2~3x), quickly leading to shut down.

[jamesharris]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

Tread carefully op, 7 blinks can also be the panel.

[tom66]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

As far as I know, that's only applicable on the newer Panasonics -- this is a pretty similar design to the TH-42PZ70BA Johnboy fixed a few weeks ago. It may well be the same fault...

[jamesharris]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

If that set is around 5 yrs old it should apply, unless I'm wrong about the age.

[rayrod81]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

Yes that is correct, 7 blinks on this model is very possibly a shorted panel. It is a 50/50 proposition.

[tom66]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

What causes a plasma panel to just fail short?

[johnboy1313]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

As far as I know, that's only applicable on the newer Panasonics -- this is a pretty similar design to the TH-42PZ70BA Johnboy fixed a few weeks ago. It may well be the same fault...

The set I fixed a while back (TH-42PZ77U) had no picture or sound. The screen primed, then shut off with 7 blinks. There's a trouble shooting guide floating around somewhere that showed that if you disconnect the SU or the SD and the set powers up you have a bad panel. If not, disconnect the SC. If the set powers up it's the SC. Mine turned out to be the SC. I'm no expert, but I can't see how the set can show a good, full picture, even briefly, if the SU or SD is bad. In my experience, there'd be no picture or sound at all if the SC was bad. Which is why I question the seller's claim. But, like I said, I'm no expert.

The trouble shooting guide for this specific set states that 7 blinks is either SU, SD, or SC.

[tom66]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

Yes, the only possible scenario I see is a faulty A Board misdiagnosing 7 blinks or an Energy Recovery circuit failure.

[johnboy1313]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

So, if I were to go see the set for myself and verify a good but brief picture, that would rule out a bad panel?

[tom66]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

Yes. It would point to D Board, A Board or Energy Recovery.

Also, a priming screen should indicate the panel is good, though I'd have to ask rayrod81 if this is necessarily true.

It all depends on whether or not the addressing period occurs before or after the initial panel priming.

[johnboy1313]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

Yes, the only possible scenario I see is a faulty A Board misdiagnosing 7 blinks or an Energy Recovery circuit failure.

I'm not seeing an 'A' board in the diagram. Is there another name?

[tom66]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

Ah, Panasonic changed the design, again. I would say the closest equivalent is the board with the microprocessor, i.e. DG board.

[johnboy1313]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

It all depends on whether or not the addressing period occurs before or after the initial panel priming.

I'm not following you here. On the Panny I just fixed, the screen would prime and then the LED would blink.

[johnboy1313]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

I just sold that other Panny too. If I were to get this one, it would have been nice to have the boards to troubleshoot with. Assuming they are the same.

[tom66]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

A plasma screen goes through four major states:

1. Initialisation, where the panel is prepared for the next subframe. All the outputs on the buffers are enabled, SC waveform passes through.
2. Addressing, where data is loaded onto the screen. Each buffer selects one line at a time. A failed panel shorts two lines together, buffer blows up because it has a short circuit between outputs.
3. Sustaining, where the data is shown. All the outputs on the buffers are enabled, SC waveform passes through.
4. Reset, where the data is erased. All the outputs on the buffers are enabled, SC waveform passes through.

The Initialisation and Reset are part of the priming process.

I just remembered. When the panel goes bad, it almost always kills the SU or SD. And a dead SU or SD would cause no light at all. So I figure you'll be OK if the panel primes, because the SU and SD are OK.

[johnboy1313]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

I wish this thing was closer. I'd hate to waste the gas to find out the owner was mistaken.

[tom66]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

How about asking them to upload a video?

[rayrod81]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

I have seen a few of these that when first powered on will briefly flash as the screen was primed and shutdown into 7 blinks. So far all 4 have been the bad panel. The 2 I have seen with a bad SC Board did not prime the screen and just immediately began blinking at power on.

I would have a hard time believing the TV is showing a picture and shutting down into 7 blinks. Either he is blowing smoke or miscounting the blinks.

[rayrod81]

Re: Panasonic TH-42PZ700Uv Momentary Sound and Picture then 7 blinks. Is it possible

According to troubleshooting guide there is a slight possibility the D board or power supply could be at fault.