Home Theater Forum and Systems banner

41 - 60 of 97 Posts

·
Registered
Joined
·
94 Posts
LOL,,,, we could really blow people's minds if we posted how to properly align a plasma. Start talking about ramp waveforms.

I've found a few shortcuts to this, but would rather not post anything about that. I do some things that are really not the proper way. Showing new people some short cuts leads to a lack of understanding of what is really happening, and how to do it properly. There are many ways to do things quicker and easier, but with out the experience to back this up, you end up with a dangerous tech. And sometimes people see me work, and think it is easy. But they've not seen the preparation that goes into what I do. I demonstrated my procedure in one of the LG training classes, after completion it was spot on with the scope. But I understand what the waveforms are doing and lacking that, you can easily damage a panel.
 

·
Registered
Joined
·
105 Posts
Discussion Starter #42
All very good points gentlemen.
While you guys were talking shop I was putting my new ESR meter together.
My curiosity got the better of me and I figured even though I would rarely use it and it might not be needed in this case I was going to keep it.

So last night I took a few hours getting this baby soldered up. I got to say I really really stunk at first.
You wouldn't believe the silly mistakes I was making. And my solder contacts looked like large globs.
But as the night went by my form started looking better and better. By the end of the night I was a pro and those contacts were looking really good (if I do say so myself).

So here is a pic of my new BLUE ESR (before and after)
 

Attachments

·
Registered
Joined
·
105 Posts
Discussion Starter #43 (Edited)
So the first thing I had to do was test the old cap against the new one.
The old one was definitely bulging at the top. I turned it over on the table for you guys to see and it was teetering like a top. So what did the ESR say?

It says the old cap reads 0.08 and the new cap reads 0.08.
According the the ESR chart, caps with a capacitance greater than 500uF should have a reading below 1.0.
So even though the cap looks to be on its way out it still registers as good.
Your guess might have been right Jim.
I still don't have a MM with a capacitance feature so I couldn't check its capacitance to see if it off.
But I will hold on to it and test it when it arrives.

Even though the cap tested good I went ahead and replaced it with the new one.
But the new one worries me because it doesn't have the slits at the top.
It might be hard to visually detect if the cap goes bad in the future.
 

Attachments

·
Registered
Joined
·
105 Posts
Discussion Starter #44
Last thing I did was hook everything back up together on the TV. I installed the SDR-D and the SDR-U spot was left empty. I fired the TV up and I got a SOLID blue light. No picture but no blinking lights.

So it seems the SDR that's off for repair is the missing link.

The TV isn't hooked up to any inputs so there woudn't be any sound but I pretty happy that nothing blew up in my face (knock on wood).

One thing that I did was to go through and test every capacitor on the PSU-2. Mainly for giggles to see what the readings would be. But to also test for caps that you guys warn me about... the ones that were bad but looked innocent. All caps tested as they should have. I could bore you all with a nice graphic I made with the values over where that caps are located but I don't want you all to think I am weird(er). :nerd:
 

·
Plain ole user
Joined
·
11,121 Posts
How did you test your caps?
 

·
Registered
Joined
·
105 Posts
Discussion Starter #46 (Edited)
How did you test your caps?
I measured the new vs old bulging caps (while they were off the PCB) with the ESR meter.
They both read the same...0.08.

Having read that the ESR meter can take readings of a electrolytic cap while the caps are on the circuit board I measured each e-cap on the board. I connected the alligator clips to the caps leads on the back of the board. They were all within specs of good caps according to the ESR chart.

I even measured the new cap after installing it on the board. It read 0.06.
This shows that the readings aren't totally immune to the effects of other components on the board.
I did not get a chance to test the old bulging cap with the ESR while it was on the board however.
I doubt it would have been any different but it would have been good to know for sure.

As I mentioned I did not measure capacitance because my new meter had not arrived yet.

I have read that a cap that tests GOOD with a capacitance meter can actually but BAD.
Now I wonder if the same is true for an ESR meter...
 

·
Registered
Joined
·
105 Posts
Discussion Starter #47 (Edited)
http://en.wikipedia.org/wiki/ESR_meter said:
Limitations

An ESR meter does not measure the capacity of a capacitor; the capacitor must be disconnected from the circuit and measured with a capacitance meter (or multimeter with this capability. Most do not also measure ESR). Excessive ESR is far more likely to be a troubleshooting problem with aluminium electrolytics than out-of-tolerance capacity, which is rare in capacitors with acceptable ESR.

A faulty short-circuited capacitor will incorrectly be identified by an ESR meter as having ideally low ESR; an ohmmeter or multimeter will easily detect this case, much rarer in practice than high ESR. It is possible to connect the test probes to an ESR meter and ohmmeter in parallel to check for both shorts and ESR in one operation; some meters both measure ESR and detect short-circuits.

ESR may depend upon operating conditions (mainly applied voltage, temperature); a capacitor which has excessive ESR at operating temperature and voltage may test as good if measured cold and unpowered. Some circuit faults due to such capacitors can be identified with freezer spray; if cooling the capacitor restores correct operation, it is faulty.

An ESR meter connected to a capacitor with significant voltage across it, either because of stored charge or in a live circuit, may be damaged; protective diodes across the input will minimise this risk (but the meter can no longer be used to measure battery internal resistance).

When used as a milliohmmeter any significant inductance present between the test probes will make measurements with an ESR meter meaningless. For example, an ESR meter is unsuitable for measuring the resistance of transformer windings. This effect is significant enough that probes with coiled cords should not be used due to their inductance.

.
Answer found. They also say that when capacitor ESR goes bad it increases by a large amount so ESR accuracy (0.06 vs 0.08) is really not an important characteristic.
 

·
Registered
Joined
·
105 Posts
Discussion Starter #48
Im still waiting for the IC to be replaced on my SDR-U. Its been a week since it was delivered and im pretty anxious to get it back. But in the meantime, i have been using this oppprtunity to:
Upgrade my surround sound wiring (from 18 to 16 gauge)
Upgrade my surround sound system from a 5.1 to a 7.2.
Giving my hookups a more finished look by using A/V wallplates instead of having HDMI and component cables sticking out of holes in the wall.
Finishing my Diretv upgrade (swm lnb with power inserter) and other wirings for a professional/clean look.

I have enough stuff to keep me busy for the rest of the week so hopefully by the time im done my board will be back and the P60 will be up and running again.

Man i cant wait.
 

·
Plain ole user
Joined
·
11,121 Posts
Accuracy is not terribly important in ESR measurements. In circuit measurements have to be understood in the context of the circuit. If there is a parallel component or circuit with a lot impedance or short, it will mask a high esr cap. If you have two caps in parallel, for instance, one with normal esr and one with high, you will read the lower impedance.

You can have a cap with good est and good capacitance value that is still bad. There are other parameters, for instance DA, that can cause odd behavior. You can also have caps that leak electrolyte that measure fine, for a while. The electrolyte can cause other issues in the circuit.
 

·
Registered
Joined
·
105 Posts
Discussion Starter #50 (Edited)
My new board came in the mail today. And when I say new I mean NEW.
It wasn't the original board I sent in.
I've spent so much time looking over these boards when I first pulled them there was no way I could not notice.
I double checked my pics and confirm.
Although it was another board the part numbers matched and a test with my multimeter showed the resistances were equal across the board... since I don't know what the specs should be that could mean the buffers are all good or all bad but I have to give it a try and email him later to ask what happened.

Unfortunately the set is still not working.
After installing the board and firing it up, the set behaved the same as when the defective buffer board was out.
Solid blue light... no picture.

I connected a A/V source to the TV to see if at least i got some sound and still nothing.

Pretty disappointed.
I checked all my connections and reseated the ribbons to the buffers.
Still no luck.

I then went to the repair manual and DW3 TROUBLESHOOTING FLOW CHARTS (power supply)



After going through the flow chart it seems my issue the Power Supply.
 

·
Registered
Joined
·
105 Posts
Discussion Starter #51 (Edited)
The next step was to test and see if the Power Supply was getting the Power On signal from the switch.
Its worth noting that the BLUE Power light is ON at all times. The remote will not shut the TV off and I have to hold the main power switch for about 10 seconds for the TV to go into Standby mode.







With my multimeter tested Pin #1 and Pin #3 on CN63 which read 5.18V and 3.28V, respectively.
Which seems to be okay.

Then I tested Pin #6 aka Power_1 (4.7V) and Pin #7 aka Power_2 (0V).
If I am reading this correctly both Pins 6 & 7 are supposed to give me +3.3V.

I finished step 4 & 5 but I didn't' get any readings off of them.

I'm not totally confident I am reading the above trouble shooting guide right though.
I am not sure what they mean (at the bottom) by "does not rise".
I'm not sure if I was supposed to toggle the TV between the On and Standby mode.
That's the only way I could conceive there be a rise in voltage....

So I am laboring under the assumption that I now have a Power Supply issue and not a Power-On control signal Issue.
 

·
Registered
Joined
·
105 Posts
Discussion Starter #52
The first thing did was look at the new e-cap I installed earlier.
Wanted to make sure I didn't do something foolish like install it wrong but the markings are pretty clear so I ruled that out immediately.

Then I looked over the whole board again. Unlike many of your boards this one is pretty big and packed pretty tightly. Another reason I am NOT looking forward to desoldering and testing each component is the solder they use is pretty strong. The solder I have melts really easy at around 250 but to get that old buldging cap off I had to crank my tip almost to the max for a minute just to get the solder to melt. I made sure I didn't hold it on too long and used solder wick to remove it but still... if I have to go through that for every little component I understand why they say just get a new board. Perhaps this is where HOT AIR shines.

One thing I did notice upon closer inspection was one of the transformers looked a little funny.
By that i mean the glue (or whatever that stuff is) looked degraded compared to the others next to it.

FUNNY LOOKING TRANSFORMER


OTHER TRANSFORMERS


The funny looking one looks as if it has seen a lot of heat and that heat has baked that glue sitting there.
The other ones look fine in comparison. Of course, this is a layman's observation. I haven't seen enough transformers to know a good vs a bad one but its just something I noticed.

I would have to take it off the board to test it and the other ones.
And as I mentioned before that isn't going to be fun because is soldered down to the board at about 10 points.
 

·
Registered
Joined
·
105 Posts
Discussion Starter #53 (Edited)
So now, Im at the fork in the road.
I have already checked the ESR ohms of the larger capacitors (albeit while they are still on the board).
Do I go ahead and start removing and testing components?

If so, were do I start?

I read somewhere that if nothing is obvious I should start with Caps, Transistors then Transformers.

With a board so packed what is the best way to go about it?
Removed, test and immediately replace? Or replace the components at the end?

I like the idea of replacing them later as it will give me a lot of room to work.
The trick of removing one leg and testing almost wouldn't work because I have so many little components next to great big components that I feel I really need the caps, transistors (with their heat sinks) and transformers completely out of the way.
 

·
Plain ole user
Joined
·
11,121 Posts
What are you missing out of the power supply?
 

·
Plain ole user
Joined
·
11,121 Posts
You said that you thought you had a problem with the power supply. Check the voltages out of the power supply and determine if any are incorrect or missing.
 

·
Registered
Joined
·
105 Posts
Discussion Starter #57
You said that you thought you had a problem with the power supply. Check the voltages out of the power supply and determine if any are incorrect or missing.
I got you.
I think I already did much of that (unless you are talking about something else).
In the few posts above I described how I check the output voltages coming from the board.
They were part of the troubleshoot guide I included.

With my multimeter tested Pin #1 and Pin #3 on CN63 which read 5.18V and 3.28V, respectively.
Which seems to be okay.

Then I tested Pin #6 aka Power_1 (4.7V) and Pin #7 aka Power_2 (0V).
If I am reading this correctly both Pins 6 & 7 are supposed to give me +3.3V.

I finished step 4 & 5 but I didn't' get any readings off of them.

I also tested the filter PWB and PSU_1 and they showed pretty healthy AC voltages going into PSU_2.
PSU_2 is the board where I found the bulging cap.

 

·
Registered
Joined
·
105 Posts
Discussion Starter #58 (Edited)
I went through and rechecked all my output voltages starting from the very beginning .... The filter PWB (where the power cord connects to the TV). At that point it reads 122V-AC as to be expected.

Then I tested the main power line that joins PSU1 and PSU2 together (its basically a pair of thick wires) and it read 50V-AC but it was dropping rapidly for some unknown reason. I held the lead of my multimeter on the live wire until it got into the single digits. Scratched my head and just stared for a minute.

Why wasn't PSU-1 supplying a constant power supply to PSU-2 when the TV was powered on (not in standby mode)??
I went back to the filter PWB and tested it again (at the point of entry to PSU-1) and conformed that PSU-1 was still getting 120V.
n
I went on to the outputs of PSU-2 and checked the ports. They were all fine according to the voltages written on the board.

Then I went back and unplugged the TV and disconnected the main power line that joined PSU-1 and 2 together along the others metal cable near the bottom. I connected my test lead of the multimeter to the live lead going out from PSU-1 and plugged the tv back in. The MM jumped up to 220v and immediately started decreasing. Within five minutes voltage was in the single digits again. By isolating PSU-1 from everything else I think I am a little closer to figuring this thing out.

I connected everything back the way it should be and repeated the exercise with the test lead still connected to the live wire. Same result. I then went over to the X-SUS and tested all the cables coming from the power supply. None had any voltage across them.

I think the culprit is PSU-1 not supply any high voltage power to PSU-2 resulting in no power going to the X-SUS or the Y-SUS.

Why PSU-1 is not providing constant power is a mystery though.
Could be a bad component although its not apparent to the naked eye.

PSU-1 gives off its familiar clicks when it powers on.
There is no sign of board damage or defect.
And the blue light is solid (no blinking).
But there is NO HEAT coming from this board.
There are large heat sinks and caution signs all over it but it its cool to the touch even after the TV is sitting with the power on for several minutes.

This board is half the size of PSU-2 and not nearly as crowded. So testing components won't bad as much of a pain.

Anyone have any idea where to start testing?







 

·
Registered
Joined
·
105 Posts
Discussion Starter #59 (Edited)
Its been a week since my last post and I wanted to give you all an update.

Happy to report that I got the TV working again but its not 100%.

First let me start by saying that I got my hands on 2 crucial documents that helped me tremendously (although I found them at various stages of the repair this week).
The first was the Troubleshooting & Repairing Switch Mode Power Supply ebook by Jestine Yong. This was a very good primer into SMPS repair and after reading (and rereading) it I was not so intimidated about tackling the troubleshooting job.

The second document I found was a Hitachi troubleshooting document titled DW-3 (42", 50" and 55") POWER SUPPLY FORCING VOLTAGE GENERATION. Its a 7 page support document written by Alvie Rodgers C.E.T. that shows you how to test your power supply by placing specific jumpers on various pins and verifying the resulting output voltages.
This takes the guess work out of knowing if you SMPS is good or bad and its how I came to my suspicions that there was a problem with my power supply.

In the last episode, after placing my new buffer board in its slot the TV would power on (solid blue light) but I got no picture or sound.
After spot checking the voltages on the PS1 (this unit has 2 power supplies) I noticed that it would power up initially only to cut out within seconds. So I took it out and starting testing the components as there were no visual signs of defect.

Desoldering this thing was a pain because I think they used lead-free solder.
I bought a $12 desoldering iron from Radio Shack (the one with the suction bulb) and it really worked well to get that solder off.
I checked all the caps both on and off the board for my own edification….they all read good.
Then I checked the diodes and resistors….those read good as well.
Just for the hell of it I tried to get those transformers off to see what I could see (and get them out of the way) but that's about the time the tip on my desoldering iron decided to give out. Getting those things off would have been a real hassle anyway. They have 10 pins and if you can't get all of the old solder completely out its not moving. After I eliminated the obvious and things that might have been easy fixes I put everything back together and put it back into the TV with the same results as before.
At least I didn't screw anything up with my teardown.

This was about the time that I stumbled across the Alvie Rodger's Forcing Voltage doc. For the 60" it deals exclusively with the 2nd power supply (the big one) where all the PDP outputs are located. I went through the steps and saw that I was not getting any voltages across certain connectors but was getting voltages across others. This told me that my PS1 might be alright after all. So I took PS2 down and to do the same thing to it as I did with PS1... tested component on and off the board.

By this time I came across Jestine Yong's ebook and took the time to read it. It helped me get a better understanding on what each component's function was and how it related to the others. Jestine also has an ebook entitled Testing Electronic Components which shows you how to test the different kind of components you are likely to run into when repairing electronics. Highly recommended! One thing I learned (and that was immediately useful) was the difference between using hot and cold ground and how not using the right one will affect your measurements.

So with a bunch of new desoldering tips in hand and my ebooks I went to town.
I focus primarily on the sub power side testing diodes, resistors and transistors.
I meticulously wrote everything down and took a lot of notes as I went along.
I pulled up the data sheets of every component I inspected to get a better understanding of them.
There was a moment when I thought I found a short across diodes in 2 bridge rectifier arrays but when I pulled them and tested them the diodes were good.
They only read as shorted (both ways) while in circuit. I spent several hours trying to figure how could this be.
Admittedly my weakness is looking at the underside of a board and understanding what's going on.
I searched for a schematic for this power supply but found absolutely nothing.
Hitachi certainly doesn't make it easy to fix these power supplies.

After I had done all that I could do with the equipment at my disposal and my skill level I decided to put it all back together again and get it back on the TV.
The ebook mentioned that there are a few components that can only be tested with power running to it (voltage regulator) and some which test only test bad when current is running through them (tests good otherwise).

When I got it back on the the TV, the first thing I did was repeat the Alvie Rodger's procedure for getting the PS to generate voltage across connectors.
To my surprise I started to get readings!
All the outputs were reading their correct voltages but I was having problems doing the Va/Vs checks.
I was able to get Va done but never got a proper reading on Vs.
The Alvie's procedure warns about this however so I just chalked it up to my inexperience.

When I hooked all the connectors up to the PS and turned the TV on I got the same result (solid blue led, no picture).
Then I disconnected all the jumpers and reconnected JUST the power switch jumper and plugged the AC back. (its the first time I connected only to power switch by itself)
Something funny happened.... the PS gave the usual 2 clicks but this time .. for the first time the 2 fans came on and stayed on.
Usually the fans would cut on for 1-2 seconds and then shut off.

I killed the AC and reconnect all the other cables.
When I turned the TV on I saw the lights in the room room dim a bit and heard a the TV fully energize.
I looked at the TV screen and I had a perfect picture! And was doing the happy dance!



I pushed to power button on and off played around with it for about 10 minutes .
I even unplugged it for a few seconds.
Powered up with no problems.

NO HERE'S WHERE THINGS GET FUNKY

When I left the TV unplugged for a while and plugged it back up, it did the same thing as before (solid blue led, no picture, and the fan cut out after a second).
I cycled the AC off and on again with the same results.
I left the tv unplugged for a while and tried it again ... same results.

I disconnected all the output connectors to the PS except the power connector (as I did before) and started the TV again. ... Fan came on and stayed on.
I then reconnected the outputs one by one to see what would happen….fan stayed on each time power was applied to the TV.
The last connector I reconnected was the power connector to the XSUS and YSUS.
When I turned the TV on it worked. Got perfect picture again.

I then did a little experiment.
I unplugged the tv for 10 seconds and reconnected it again…..GOOD (picture and sound came on with no problem)
I unplugged the tv for 20 seconds and reconnected it again…...GOOD (picture and sound came on with no problem)
I unplugged the tv for 30 seconds and reconnected it again…..BAD (Solid Blue LED, NO Picture, NO sound and No Fan)


I repeated this experiment about 2 times.
I determined that if the AC was disconnected from the TV for more than ~25 seconds I would get a solid blue led, with no pic and no sound.


If I am interpreting the symptoms correctly this is CLEARLY some sort of DISCHARGE issue.

Luckily I then figured how to recover the TV from this state.
All I had to do was unplug the TV, disconnect the XSUS & YSUS from the PS, reconnect the AC, turn on the power via the power swtich, unplug the TV again, reconnect the XSUS & YSUS and power the TV back up. Then everything works fine.

For clarification, the cable that feeds XSUS and YSUS from the PS is one cable.
That cable runs directly to the XSUS.
The power to the YSUS is supplied via another cable from the XSUS.
In an attempt to isolate the issue I have tried unplugging the power to the Y-SUS (from the X-SUS) but when I turn the TV on there is audio for a split second (and possibly a flash of video but I can't see it from back there) until the TV realizes there is no Y-SUS and the TV cuts out.
When I unplug the the connector to the Y-SUS (which feeds both Y-SUS and X-SUS boards) and activate the TV I get 4 blinking LED error which is to be expected.


The fact that I have perfect picture quality (when the picture is present), no signs of damage on the X-SUS and Y-SUS boards makes me feel the power supply the culprit.
I truly believe that the 25 second power symptom is the key to figuring out this issue.

At the moment I have a working TV as long as the power doesn't go out for more than 25 seconds.
Even if it, buy unplugging the X & Y sustain I seem to be able to get it back running again with no problem.

Because the extreme difficulty of unmounting this unit from the wall (200 lbs) and removing the back panel (60+ screws) every time the power goes out what I have done for now is to cut a small access panel on the back cover so I can reach that connector whenever I have to. My plan is to keep it covered with a black wire mess.



I'm not worried of about the aesthetics of the back panel too much but I will try to make the finished product look descent.
It can even double as a vent for extra cooling. I am also not worried about resale value either. Because of its size and weight selling it would be pretty difficult. This unit is going to stay with me until its other 3 wheels fall off and then it'll be parted out for the benefit of other P60 owners out there. Hopefully that won't happen for many years to come!

If it is a power supply issue then my choices are pretty limited but I am glad I have the opportunity to get more life out of the unit.
Without assistance further component level diagnosis is probably out of my league.
Finding a replacement PS is near impossible and having it repaired by even the most qualified technician is going to be a challenge for a number of reasons.
Primarily because the technician will almost undoubtedly have to have this TV set with them in order to make the repair and test their work.
Remember this has 2 power supplies which run in series and the symptoms (solid blue led, no picture) manifests itself on the TV and not on the PS itself as far as I can tell.
The hard to find or non existent schematics and support is another problem.

I am not satisfied with the current state of the TV as it is.
I would like know what the problem is so I can fix it.
I have a feeling that if I don't resolve it it will lead to other failures.

I'm going to do more research and see what other ideas are out there.
If you guys have any please feel free to share.

I'm going to hold off remounting the TV until i have reasonably exhausted all ideas on what the issue could be.


Thanks!
 

·
Plain ole user
Joined
·
11,121 Posts
My guess would be a cap with bad DA or a reset circuit that is malfunctioning. DA is also known as "battery effect" and will result in a cap voltage RISING after it is discharged. It can create some unusual effects and is not uncommon, even in new caps. A DA of over 15% is considered bad, but I have tested caps at around 10% that would not work in some circuits.
 
  • Like
Reactions: KYBOSH
41 - 60 of 97 Posts
Top