Mulja tv repair portal
Equipment Repairs => PLASMA TV forum => Topic started by: tns1 on June 18, 2012,17:12:35
-
Apparently there are hundreds of plasma sets from this era that die in the same way - no picture, 10 blinks. Hopefully there are only a few root causes to explore.
When the set is first plugged in, I believe I get the normal 3 relay clicks - two quickly and a third after ~15secs. The LED is no flashing at this time. When I push the power button, I get some relay clicks, the fans power on for just a second before the set shuts down and the LED flashes 10 times repeatedly.
Holding the power button down does not get me any further.
I am trying to follow the service manual, which has great schematics, and board pics, but does not provide diagnostics or explanations of the power up sequence. For instance the code table pg26 lists 4 SOS conditions associated with a 10 blink code:
Sub 5V SOS, Main 3.3V SOS, DTV 9V SOS, Tuner Power SOS, all with the check point being the DG board.
It took awhile to realize these 4 conditions come from different places, possibly different boards.
Some of those SOS conditions are come from the P board, some the H board, some the DG board.
I would have thought that for a power problem I would first check the power board. Is there a way to verify the power board operation without the other boards attached, or is this not practical?
-
You would need a power on signal to turn on the power supply. This comes from the micro. you should be able to disconnect other boards without a problem. It may be posssible to simulate the power on signal, 1k resistor from the 5v stby supply?. This does not always work though.
Mark
-
Thanks. I am beginning to understand how the power circuits work. I can see that most of the power is OK, such as the STB5V, and the related 9V,5V,3.3V,1.2V,1.8V, 30V. Many of these only appear in the short time before SOS shutdown, but I believe they are in range.
One or two other voltages are not as expected. The power board should be generating 15v and I don't see that, I am also not seeing the P5V either, and it isn't clear what this depends on outside the power board.
-
When I press power on, I see the MAIN Power ON signal (aka Panel ON), is correct but the Vsus and Vda do not get generated, even with the SC SS panels unplugged.
All of the low voltages seem present, but what I see is the P+15v and P+5V appear, but are dropping out 100ms before I get an SOS, suggesting that one of the many voltages/currents are out of range.
The 15V was 15.8V so I adjusted it down thinking it may be too high - did not fix. How far off can these voltages be before the various SOS protection kicks in? 10%, 5% ? I have 5.3v and 9.22v - are these too high?
There is an EHMDD9851, dual 5v,9v regulator I would like to find the datasheet for.
The relays on the Vsus power board never turn on, but it is difficult to say if the fault is on that board, or if the required signal inputs are just not present. Being able to test each power board independently is essential. What external power/signals are required to turn on the Vsus power board?
-
You need to be checking Vs control module MC301 on the power supply (P board). On it you will note a TEA1611 chip. Off pin 13 of that chip is a 1uF surface mount located to the left of the upper left corner of the chip.It becomes leaky and curtails the operation of the TEA. You should find plenty of info on the internet about this fault. It is well documented. Most 10 blink errors in these are caused by this capacitor.Replace it. If it's not the cause, you will have lost little.If it is the cause, you will have gained much.
-
Those posts mainly apply to 42" sets. The TH-58PZ700U uses a 2-part power board. It does have an MC301 module but it is a 25pin rather than the smaller module discussed. Mine uses the TEA1610T (a 16pin part) rather than the TEA1611T. This is the same type of regulator, with the same purpose (15v generation), so the Vdd capacitor is still worth investigating. The additional info/diagnostics in these posts is a good find.
Thanks.
-
Simply replacing the two Vdd ceramic caps on the MC modules did not solve the issue. I can see that the bias voltage reaching the TEA1610 chip on MC301 is only 11v, not high enough to start it. It is possible the chip or other smd parts are leaking. As I mentioned, the MC modules are a different design than the ones referred to in the many posts about leaky caps. It may be those caps aren't the main problem on this model.
Since it seemed likely the power board was the issue, I found a used one for $150. That fixed it. I replaced the two Vdd caps (MC201, MC301) on the replacement board as a preventative measure. On models with the 2-part power board, this is simply done with no need to unsolder the MC modules.
If I have another failure, I now have more parts to experiment with.
-
Most curteous of you to post feedback and outcome.