I have run across this problem several times and was hoping for some insight...
In regards to lcd tv/monitor:
The tv has a bad picture ie wrong colors, rainbow like color distorsions etc but the osd and menu show up correctly. Is it wrong to assume the tcon board is good if the osd/menu show up correctly? I assume the problem lies within the main logic/display board. Is this assumption correct or could the tcon still be suspect?
Thanks.
aliasdck
Senior Member
Last Activity: 12-26-2011, 12:50 AM
Joined: 09-17-2009
Location: California
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general troubleshooting advice on lcd tv
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Re: Need some help indentifying this smd diode
I found it! It is a diode, but not what I was originally thinking...
It is a bi-directional transient voltage suppressor diode which makes sense considering the circuit it was used in
Anyways, here is the datasheet for a replacement in case anyone out there ever comes across this and needs it:
[url]https://cdn.badcaps-static.com/pdfs/813cbb6aa5259d94d08c4c679024cbf9.pdf[/url]
Part number is SMCJ20CARe: Need some help indentifying this...br /> I found -
Re: Need some help indentifying this smd diode
This is NOT a diode.
I made the incorrect assumption it was a diode based on my IN circuit testing. I knew better than this, but I got lazy and assumed it must be a diode since it was labelled D3 on the circuit board and I was reading .397 in one direction with the diode feature on my multimeter. Out of circuit it reads open in both directions.
I've been sifting through page after page about smd codes, manufacturer logos etc. Never was able to find anything based on what is imprinted on the device while...Leave a comment:
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Re: Need some help indentifying this smd diode
Forgot the attachment...Leave a comment:
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Need some help indentifying this smd diode
Check the picture for the component in question. I am unfamiliar with the markings on this component so I need help identifying the manufacturer so that I can hopefully find a datasheet.
The only thing I know so far is that it is a diode (atleast I hope I'm right), and its forward voltage drop is reading .397
Thanks
Last edited by aliasdck; 07-30-2010, 06:04 PM. -
Re: Is this new capacitor ok?
There is no maximum esr rating for the new cap in the KMQ datasheet however there is a maximum ESR rating for the old cap in the KMH Series datasheet.
The maximum ESR for the KMH Series capacitor is 1.13 ohms @ 20 C @ 120hz. Since I am testing both caps with an esr meter that is using a test pulse of 2khz, I don't think I have much to worry about since both readings are well below this.
I was just concerned since the new caps esr was double the old cap but now I suspect it may just be due to different design/makeup (The...Leave a comment:
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Is this new capacitor ok?
I am in the process of recapping a power supply for a large 3 phase UPS. I just had one question concerning one of the caps I received from digikey.
I have attached a picture of the cap. On the left is the original cap... there is nothing wrong with it, but I have been asked to replace every cap on the power supply since a couple of the smaller secondary caps failed. The cap in the picture is on the primary side rated 220uF 450V.
The cap on the right is the replacement I ordered from digikey. As far as I can tell, the cap I ordered was nearly identical in specifications...... -
Re: 50" Mitsubishi Plasma TV
I have trouble articulating the symptoms so I must apologize...
The tv displays a perfect image whenever the majority of the display is black... for example, when there is a small logo on a black brackground. But when the majority of the display is a bright color then the image becomes noisy and dark. A full white screen is very dark and it appears the display is struggling to illuminate.Leave a comment:
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Re: 50" Mitsubishi Plasma TV
Hooked up the scope again today and did some more investigating.
I must have been doing something wrong last time as both sustain waveforms look good. I had y sustain on channel 1 and z sustain on channel 2 and everything looks appropriate.
I'm beginning to suspect the control board. I followed the troubleshooting guide for an LG plasma set and it suggests the control board as well... (this display is NEC).
Guess I might buy a control board (logic board) but I'm not 100% sure this is the problem yet.Leave a comment:
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Re: 50" Mitsubishi Plasma TV
Needed a good enough excuse to give to the wife
So I got a new scope and had a look at waveforms today. Not 100% sure what I am looking at here as I am not familar with NEC panels. I found a service manual for this tv but it does not provide any waveforms or service information for the y,x or z boards. It only contains service information for the power supply and logic boards.
But I am familiar with what the waveforms on an LG panel look like and I have been using...Leave a comment:
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Re: oscilloscope probes
Thank you for your advice.
I just acquired a tektronix 475 a couple of days ago. I'm not going to bother trying to find better probes as it sounds like my current probes will be sufficient.
Let the testing begin...Leave a comment:
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Re: Dell W1700
I picked up a dell w1700 at a local ewaste recycler a few months ago. The power led would light but the backlights would not fire.
Opened it up and found a blown inverter fuse. I probed around and discovered that one of p and n channel mosfets (single package containing both) that drive one of the inverter transformers was shorted. I replaced the fuse, the mosfet ic and also the caps on the board for good measure.
Now this tv/monitor works but unfortunetly it has a horrible red tint due to aging bulb(s). I have put it aside for a rainy...Leave a comment:
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Re: Benq T701 and unknown fet's smd code
I haven't been able to find anything based on what you've provided.
Is it possible it is the reset controller for the microprocessor? How is it labelled on the video board (for example D13 or U10. A picture may help us identify it).
What symptoms does the monitor exhibit?Leave a comment:
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Re: Zenith HDV420 Won't Come Out of Standby
I over looked the fact that you were talking about a set top box and assumed you were talking about a tv.Leave a comment:
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Re: oscilloscope probes
Currently I need a scope capable of looking at setup and setdn waveforms as you mentioned. I'm glad to hear 100Mhz is plenty for this application though ill likely still try to find a 200mhz.
I've been searching ebay for used scopes. Most of what I've come across in my price range do not include probes. I'm thinking about getting a tektronix 475 but haven't made up my mind yet.Leave a comment:
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oscilloscope probes
I have some cheap (~$20) generic 100Mhz oscilloscope probes. I am currently looking for a used 200Mhz scope but Im wondering what type of probes I should consider getting for it. The probes I've found so far are all very expensive (over $100 each). Anyone have any recommendations on which probes I should get? I'd rather not spend too much money if I don't have too.
I plan to use the oscilloscope to help me diagnose problems in plasma tv's... service manual recommends 200Mhz scope. -
Re: Zenith HDV420 Won't Come Out of Standby
I am curious what the red and gray wires you have jumped together are labelled as on the powerboard. I can't make it out from the picture. I don't want to jump to any conclusions without understanding why this "fixes" the problem but it may not be such a good idea to override any safety features that have been designed into this tv.Leave a comment:
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Re: 50" Mitsubishi Plasma TV
I have checked the power supply outputs and they are correct and stable (both when the display looks normal and when it is bad).
I am unable to check waveforms on sustain cards... my scopes bandwidth is only DC to 10Mhz. I want to buy a used 200Mhz scope... maybe this is a good enough excuse to buy one....Leave a comment:
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Re: 50" Mitsubishi Plasma TV
I finally got some more time to play around with this TV today.
I was wrong in my original description of the problem. The OSD does not always show up correctly. It depends on what else is being displayed on the screen.
The TV will show a good display whenever the majority of the display is black. For example, my computer screen saver (black background with just the windows logo moving around) shows up perfectly. Colors are rich and vibrant. The OSD/Menu shows up bright and well defined during this time.
...Leave a comment:
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Re: 50" Mitsubishi Plasma TV
Can't sleep... hate being away from home.
The problem occurs on all inputs, and yes all inputs are analogue. Its an early set and probably not worth repairing but this is strictly a hobby for me at this point... I'm in it for the fun of it and for the learning experience....Leave a comment:
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