LCD Monitor stopped working. :(

[nwg]

I definitley have decided I would like a widescreen monitor. Does anyone know if the Geforce 6100 on baord graphics can do the required 1440 x 900 resolution?

Looking at the resolutions in the display properties, it goes from 1360 x 768 to 1600 x 900.

[Chewy]

http://forums.viaarena.com/messageview.aspx?catid=31&threadid=73756&enterthread=y

no option to add an agp card?

[atifsh]

yes it would do im sure as ATI 9200 can do that resu...

[nwg]

Thanks for the link but I already seen it and didn't see what help it coud be. I can already do custom resolutions with NVidia software.

My board will do PCI Express but I have no intention in getting a graphics card. I don't play games so I don't need the extra hardware. I would also reduce the amount of airflow in my small case.

I saw a 19" HP widescreen and wasn't that impressed. It looked nice and had a stupid advert on it rather than windows. It looked small and I was expecting bigger. I have a 15.4" widescreen on my laptop and it really didn't look much bigger. I think I will go for a normal 19" monitor.

[Mercur]

I had exactly the same problem with my Hansol H711. Problem started as intermittent dark section on the screen. After e few days completely dark screen. Cause: No 12 VDC from PSU when under load. Cause, defect capacitor C7 value 820 uF 16v. Its fitted in the PSU. Easy to replace.

[nwg]

I had exactly the same problem with my Hansol H711. Problem started as intermittent dark section on the screen. After e few days completely dark screen. Cause: No 12 VDC from PSU when under load. Cause, defect capacitor C7 value 820 uF 16v. Its fitted in the PSU. Easy to replace.

Interesting. I am pretty sure the psu is ok (even if it is the second one I have had). Did you still get the green light on? The psu is only just over a year old.

It did'nt start intermittent. One minute is it ok and the next it isn't.

[Mercur]

When the problem started the green LED was still alive. But later when the screen was completely dark the LED was OFF. It took some time to find the fault. At first I did not suspect the PSU as I could measure 12 VDC at the output. But connected to load the voltage drop to just 2 volt. So went into the PSU and detected the suspected cap. Took it out from the board and meassured it to have an extreme low capacitance. I had a 1000 Uf 16 v in the junkbox and the monitor is now "as new" again. Saved a lot of $$$.
Caps are normally the first to look at in a defect switched PSU. Your problem is most likely also related to a cap problem , perhaps the same cap.

[nwg]

When the problem started the green LED was still alive. But later when the screen was completely dark the LED was OFF. It took some time to find the fault. At first I did not suspect the PSU as I could measure 12 VDC at the output. But connected to load the voltage drop to just 2 volt. So went into the PSU and detected the suspected cap. Took it out from the board and meassured it to have an extreme low capacitance. I had a 1000 Uf 16 v in the junkbox and the monitor is now "as new" again. Saved a lot of $$$.
Caps are normally the first to look at in a defect switched PSU. Your problem is most likely also related to a cap problem , perhaps the same cap.

The green LED ok and not off though when it is dark. It seems I am getting different causes by people. Another one is the inverter has failed which turns lights up the backlight.

[RFBurns]

Hello everyone!

Back again for another week of work and play.

Im very happy that folks are finding my tips and info useful, and I will continue to post as much electronic related info as possible. If even just one member finds the info to be of help, that is a greater reward to me than anything else.

Here is another tip for all the do-it-yourself'ers. (Disclaimer below!!)
Sort of long post...sorry about that. Just lots of info.

Capacitors...

There are 3 main types of capacitors in typical electronics. The ones most common and prone to failures are the Electrolytic types. They contain a fluid compound with zinc and aluminum plates dipped into the canister. The plates are seperated by a thin insulator. Capacitance value is determined by the size of the plates, and the seperation between them from the insulated material. A good example of how that works is by examining the old "AIR" tunner variable capacitor found in many older home stereo units that used the air tunner variable to allow tunning of radio reception. These types are not electrolytic but are mentioned so that one can observe the capacitor plates and how varying capacitance can work.

What makes the electrolytics go bad...and this is kind of crazy because us engineers know better, is that designs of devices call for plenty of "head room" when it comes to component tolorance, thus we make sure the design can go a certian range byond center tolorance...ie plus or minus a precent value...+-10% for example. So the overall design has plenty of "room" to allow proper operation over a varying range of parameters, including voltage swing, component aging, temperature change, humidity factors, and load (work or use) variances.

The primary problem is this.....manufacturers will find the cheapest parts a device can use, ie capacitors with LESS tolorance, less voltage swing tolorance, less temperature tolorance and so forth. Thus the capacitor will run at its peak capability even on the conveyer belt as it goes along during testing and final assembly at the plant. This kind of manufacturing process makes the final bottom line as big as possible.

The part ends up working byond its tolorance long before the unit's time, and as a member here posted regarding the 12vdc rail down to 2vdc under load, the capacitor could not handle the filtering charge/discharge cycles during load conditions, thus basically it became a large screwdriver put across the terminals of a 12 volt car battery. SPARK!!!

Most canisters of electrolytic capacitors are designed to "buldge" when it goes bad, mainly the top part of the canister. It has indentions to allow the canister to "pop" open instead of the entire canister "exploding". Older capacitor canisters used to literally explode, spreading fluid, paper insulation, capacitor plates and pieces of the canister itself all over the inside of a device, and often causing more damage than it would have had if the canister just "blew its top".

The thing to watch for when suspecting a bad capacitor is looking very carefully at the top of the canister and the shrink wrap. The shrink wrap is the first sign of a capacitor fixing to fail. It will appear streched, and almost not covering the top section at all and making its way down the sides, distorting the writting on the sides. Also the very top of the canister may appear buldged. These two basic signs are definately signs of a bad capacitor fixing to "blow its top".

The thrid indication to look for is leakage of fluid at the base of the capacitor. However this is not easy to spot since some capacitors are "glued" at the base to keep the capacitor stable. Corrosion from leakage looks grey-black in color, and can and often does cause corrosion of nearby parts and their leads. The leakage may also cause damage to the printed circuit board and the foil traces. If this occurs, especially on a printed circuit board that is multi-layered...ie a board with foil connecting patters on top, bottom and sandwiched inbetween, it may have caused permanent damage to the printed circuit board and might not be recoverable.

When replacing capacitors, you can always go in with a capacitor that has a higher voltage rating than the original. You can also go higher in value, but that depends on what kind of circuit the capacitor is involved with. If it is simple power supply filtering at the outputs, you can play with higher values to give smoother filtering. If however the capacitor is part of a circuit like an oscillator or phase lock loop or even coupling one circuit to another, its not a good idea to change the value rating, higher or lower, because in that case the value is vital to the operation of that particular circuit. Going higher with the voltage rating is ok though. Be very observant as to what circuit the suspected bad capacitor is in and what the circuit does.

Please by all means do not attempt to "take on the world" if you are not sure or comfortable working around voltages and electronic parts/modules. Some parts/modules may have potentialy lethal voltages on them or generated by them and extreme care MUST be taken. Even in today's mostly digital electronic devices, one can be amazed at how much "zap" voltage is generated by a throw away film camera with a flash. And the voltages generated by the small ballast driver boards on LCD pannel monitors/tv's can give quite a bite if not observant of the high voltage leads and taking proper precautions.

DISCLAIMER:

I, Digital Video Forums, its owners/operators/sponsors, or any member or administrator/moderator cannot be held responsible or liable for any damage, personal injury or other resulting in improper obeservation of safety procedures when doing "do-it-yourself" repairs on your own equipment. No guarantee is implied on any repair work or suggestions found in these posts. Each instance of repair is unique and information posted within is general in nature. It is always a good idea to consult with or have a trained technician perform the repairs if you believe it is byond your abilities to do the repair safely.

There are lots of websites on the net with great basic electronic information to "self train" the curious or even the beginning electronic technician/engineer to launch their career. And as always, I will be here to give information to the best of my ability in helping anyone who needs it.

[toomanycats]

Polarity in electrolytic caps in crucial. the solid line is the negative side. The lower the value the less punch but faster discharge rate. I wouldn't replace a polarized cap with a bi-polar cap though I have seen some people do it. Caps can be used to pull voltages down to ground without actually grounding the circuit so be careful about jumping any circuit you could short it out unintentionally. M and M candy colored Caps are usually the cheapest.

[RFBurns]

Polarity in electrolytic caps in crucial. the solid line is the negative side.

Good catch toomanycats! I should have noted about polarity. My bad!

Indeed, observe polarity when replacing electrolytic capacitors!!!!

I wouldn't replace a polarized cap with a bi-polar cap though I have seen some people do it.

Sometimes this can work if the voltage across the capacitor points is low. Replacing a bi-polar or non-polarized capacitor with two end to end polarized caps can also work, providing the combined capacitors match the value and voltage of the polarized original. Again this can be safely done in low voltage non-critical circuits. But most circuits using non-polarized and bi-polar capacitors are special in nature and its design calls for the exact replacements.

M and M candy colored Caps are usually the cheapest.

There is another definition for those little bead looking or M&M colored caps....

...."Bird Tird Caps" !!! (some of us at the developing division came up with that because Sony used these little brown bird dropping looking capacitors in some of the direct view 27" and 32" trinitrons)

And some nifty re-definition value names too!!

Picofarad, Microfarad, Farad etc.......

Picofarad-Picofart
Microfarad-Microfart
Farad-Fatfart

I apologize if the above definitions is offensive in nature to anyone, it is not intended to be so.

[toomanycats]

RFBurns: So what's the deal with the 1 ohm resistor in the Sony TV power supplies and the weird disc capacitor there? I think their should be a hardware section in this forum especially with acces to people like RFBurns. Anyone who has done repairs knows info is hard to come by as is decent repair rates and services. Some people may want to adventure and try a repair on their hardware, and why not, if your going to toss it anyway.

[RFBurns]

RFBurns: So what's the deal with the 1 ohm resistor in the Sony TV power supplies and the weird disc capacitor there?

Hi!

Ahh....that one! The KV27/32 S series set, AA-2 chassis. Green or black in color. However, they are not exactly capacitors.

Those little puppies are "varistors". They are placed into the primary power supply "chopper" circuit to help regulate the operating voltage of the chopper circuit during temperature changes, sort of like a power phase lock loop. When the two transistors mounted on the heat sink (2SC4834) begin to switch at set power on, the varistors act much like the varistor across the picture tube degauss coil. Here is the theory...

A varistor is a varying resistance component that changes resistance with temperature. As it warms up, its resistance increases. As it cools, the resistance decreases. A load must be placed on the varistor for it to function correctly. It acts like a volume control, changing level of signal, or in this case, voltage as the component gets hot because of the load. In a degauss circuit, the degauss coil only needs to turn on for a few seconds when a CRT type television is turned on, removing any build up of magnetic field from the CRT so that the whole surface of the viewing screen is "demagatized".

This helps keep the 3 color beams consistant as the beams travel across the screen surface. Commonly known as "purity". As the name implies, the varistor in the degauss circuit controls the demagnatizing coil or degauss coil so that the color "purity" is consistant on the entire screen surface. If a degauss circuit is not functioning or if its varistor is not working correctly, the result is improper color at various points on the screen surface.

We can cover CRT beams and so forth later.

CAUTION!!! THIS CHASSIS HAS A 'HOT' GROUND, MEANING THE AC GROUND AFTER THE RECTIFIER IS NOT EARTH GROUND, AND CARE MUST BE TAKEN WHEN MEASURING VOLTAGES BETWEEN CIRCUITS THAT ARE CONNECTED TO THE 'HOT' GROUND VS CIRCUITS CONNECTED TO THE EARTH OR 'COLD' GROUND. AN ISOLATION AC MAINS TRANSFORMER IS RECOMMENDED BEFORE ATTEMPTING TO MEASURE VOLTAGES BETWEEN THESE TWO GROUND POTENTIALS!!!

The varistors in the AA-2 chassis power supply controls voltage to the two switching transistors Q601 and Q602 (2SC4834) via the switching transformers T605 and T603. The varistor (VDR601) is connected between pin 2 of T605, then passes through a 10 ohm "fuse" resistor R622, then on to pin 1 of T603. The insertion of a varistor on this circuit path regulates the raw B+ voltage which comes from the rectified AC input through D602, a full bridge rectifier which takes the 120vac and turns it into about 175 to 190 volts DC, filtered by capacitors C606 and C607. Pin 3 of T605 is connected to the emitter (Q601) and collector (Q602) switching transistors which make up the switching system for the power supply. Its return path, or "hot" ground path comes from pin2 of T603 and connected to the ground side of the main AC rectifier bridge D602.

A second fusable resistor of even lesser value, R607, which is a .1 ohm fuse resistor, is where the positive potential of the raw B+ is located and feeds the collector of Q601. There are other components that make up the switching power supply as well, such as those "bird tird/M&M" capacitors C609/610/611/612. These little stinkies help set up the oscillation frequency and resonance of the circuit, making it a "tuned" circuit much like a radio reciever's oscillator or a transmitter oscillator.

In this chassis, the degauss coil is controlled not by a varistor, but by a relay RY601 which is turned on and off by Q644, feeding 120vac to the degauss coil for only a few seconds to demagetize the picture tube. The degauss control transistor gets its command to turn on and off from the microcontroller located on the main PC board "A". The microcontroller is IC001.

I should point out something very important on this chassis. The primary power supply, unlike some other slightly older sets, is constantly "ON" when the AC power cord is connected to AC. The supply is constantly running so that "stand-by" voltage is generated (5vdc) to the microcontroller and a couple other IC's. This allows the unit to be turned on by its remote control and the front pannel keys. There is no switch that disconnects the AC voltage from the wall like older sets used to have. The front pannel keys, ie power/volume up-down/channel up-down/tv-video are all at 5vdc potential all the time. Each key has a specific resistor value tied in series to a common "key bus" that feeds IC001. Much like a data buss in a computer, or more commonly known as a "serial buss". 5vdc is also fed to the IR reciever IC003, which picks up the infrared light pulses from the remote control and feeds those command pulses to the microcontroller IC001. The stand-by voltage is regulated by IC642.

You might notice the many electrolytic capacitors in this power supply, common for switching type power supplies not unlike one found in a computer PSU, except that in a computer PSU and on its mobo, many filter capacitors are used to keep the voltages as clean as possible for computers. This chassis has a very well regulated and cleaned DC side of its power supply, and there are other extra filter capacitors to help keep the supply rails clean throught the set.

There is also a chassis that is about 2 years older than this one that uses 2 varistors and 1 fusable resistor on the main power supply. But in that chassis, the power supply is turned off even when the AC power cord is connected. It is a slightly different design and stand-by voltage is generated from a very tiny rectifier/fuse resistor/varistor arrangement. But the primary power supply design is basically the same. (AA-1 chassis-KV27/32TS series)

I think their should be a hardware section in this forum especially with acces to people like RFBurns. Anyone who has done repairs knows info is hard to come by as is decent repair rates and services. Some people may want to adventure and try a repair on their hardware, and why not, if your going to toss it anyway.

That sounds like a great idea. It would be a place to find technical information and advice and keep me from posting extremely long posts in the other topic areas of the forum!

I can even provide images of sections of schematics related to the discussion and information to help with component location and circuit design/functions. And the images would not infringe on any copyright, since all service literature of any make or brand of device can be found on the internet and obtained directly from the manufacturer by anyone who wants them. There may be a time or two when an image of a circuit may not be available or feisable to post. In such cases, a "best description" alternative would be posted.

Again tho, I must stress...and I am sure the admins/mods and owners/operators would agree...that this forum, its admins and mods, owners and operators/sponsors and any other members including myself, cannot be held responsible for anything that might happen from the advice/tips/suggestions followed by anyone attempting a repair from the information posted. Anyone doing "do-it-yourself" repairs on electronic devices must accept the fact that it is yourself doing the repair attempt, not me, not other members, not this forum, its owners/operators/admins/mods or any of its sponsors.

If the forum puts up a technical section which deals with component level repair attempts on ANY electronic device, anyone and everyone thinking of following the tips/suggestions etc MUST accept any and all risk and not hold anyone else liable except for yourself doing the repair.

With a little paitence, carefull planning, and fact finding prior to even taking off 1 screw from the cover, many repairs can and have been done by owners of electronic equipment within their own homes and saving tons on repair bills. This was a common practice back in the "hey day-old school" era of electronics. This by no means is intended to bypass or put service shops and independant service technicians out of buisness or work. There are repairs that simply cannot be done by the do-it-yourselfer, such as a CRT replacement and alignment, digital convergence setup on a projection tv, optical pickup replacement on a DVD or CD recorder. Some repairs are way byond the ability of the home shop. Examine the situation fully to see if the do-it-yourself method will work.

Many publications were aplenty that assisted the home repairer/hobby/tinkerer. And those publications included Popular Electronics, Radio Electronics, Computer Electronics and some others.

A good place to start and learn the basics is the publication ARRL handbook, published by the American Radio Relay League, a "HAM" radio organization that has been around for a very long time and has helped many people self-teach electronics and radio principles, and even helped folks obtain their FCC amature radio license. Many of the folks learned how to build their own radio rigs, antennas, transmitters, recievers, and even a few odds and ends or "black boxes" that eventually became patented and marketed! One example of that is the well known little box called "Video Stabalizer"!! Even the newest one, the DVD video stabalizer is a device designed and built by a home electronic hobbiest/tinkerer!!

Would it interest anyone to know, that today's cell phone is a spin-off of a ham radio device designed and built by hams? The wireless networking and wireless internet systems as well?!! Yep! Many electronic devices in a vast number of applications used in every day life came from ham radio operators and experimenters "tinkering" in their hobby shack, or as the hams call it, their "radio shack"...not to be confused with the store Radio Shack!

Anyone remember the "Mr.Microphone" toy? That was designed and built by a ham radio/electronic enthusiast. The wireless video/audio sender is another example. Lets see....GPS, satellite TV, stereo FM, stereo AM, balanced audio IC's, push-pull amplifier designs, brick-wall/bandpass filters...

I could go on but I think this post is already breaking records for the longest post ever posted!

[toomanycats]

Judging from some of the technical questions people have posted it would seem a good idea to have a DIY section from information relating to hardware. People are already offering advice on opening computer case (though I have yet to read mention about grounding yourself first!) so it would be good to capitalize of some of the knowledge in this forum though you wouldn't want to be grounded around high voltage!!}. I wonder what the next step would be?

P.S. Was that a standard 125VAC varistor?

[RFBurns]

Judging from some of the technical questions people have posted it would seem a good idea to have a DIY section from information relating to hardware. People are already offering advice on opening computer case (though I have yet to read mention about grounding yourself first!) so it would be good to capitalize of some of the knowledge in this forum though you wouldn't want to be grounded around high voltage!!}. I wonder what the next step would be?

Perhaps members submitting requests to the forum administrators, and maybe if they get enough requests, a DIY section would be created.

P.S. Was that a standard 125VAC varistor?

No. The voltage measured at this point is raw B+ of about 175 to 190 volts DC. The numbers on the varistor, mainly the first 3 digits, give the components maximum working voltage rating. In this case, VDR601 is a 430 volt varistor. It can safely operate up to that point. Anything byond that and it goes POOF!!!

This is a good example of what I spoke about in another section of the forums. That we engineers design stuff with plenty of headroom to account for all kinds of variations in operational environments and parameters. If there was only a 125 volt varistor in there, as soon as the set got plugged in, that varistor would recieve at minimum of 175 volts DC on it, 50 volts higher than a 125 volt varistor could handle, and it would get very hot very fast and soon go POOF, short and cause a major catastrophic failure on that raw B+ rail and chopper circuitry, and possible damage byond the power supply.