Question about Mitsubishi VS-50605 50" Rear Projection Television

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TV problem D955 and D953 seem to check good out of circuit with both analog and digital meters. Tell me what is correct way to check for leaky diode? REDCAT55

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Use the analog meter reverse your probes you should get no reading one way and get a reading when the probes are reversed. You will need a diode vhecker to test for a leaky diode as often times a diode will fail under load. Its best to replace a questionable diode if you dont have an actual diode checker meter.

Posted on Mar 08, 2008

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My misubishi ws-65809 would not turn on and had the 2-2 blinking light self test. I pulled the convergence board to replace the IC's and when I inspected the board I found that a diode in the middle of...


Hi, well when testing a diode you DO NOT use the meter set to OHMS, indeed you need to use a meter with a "Diode test" feature, you see when using a test with only OHMS, it will NOT supply enough current, unlike the diode test function, to bias the junction correctly, and give you the proper reading. Using OHMS only will and does give erroneous readings always.
Now as to the problem, i see where another person has jumped on the old "Capacitor" bandwagon, if only all faults were so... look without inspecting the unit and taking voltage and current readings it is simply frivolousness to state such a thing unless one has direct knowledge of the fault?

Look to effect ANY repairs one simply MUST obtain a service manual and start with the Power supply and check the voltages there and work out, there simply is NO other way.
The fault you describe may have a myriad of reasons why the unit is doing this "Fault" there is NO shortcut, NO magic method of diagnosing anything OK. With a problem like this unless VERY experienced, one should simply replace any suspected boards, "On Spec" as it were.
Before we can attempt to repair anything at all, there is one thing that one MUST do before anything else is done. Now that is, the making sure that the Power Supply,of the unit, no matter what it is, has the correct Voltages, coming into it, and more importantly, coming OUT of it. This is absolutely imperative, as, IF these Voltages are NOT correct then NOTHING will work, properly at all. So we must measure these voltages with a Volt Meter. All Voltage measurements are made with reference to ground. Meaning we clip, our Black, Minus, Lead onto the Earth, or Chassis, or Negative (-) "Rail" of the Power Supply. Now with the Red lead, we can now, measure these Voltages. Now sometimes, the Voltage of each Output is annotated,or written, onto the PCB, that will indicate the Voltage of that output. However most usually they are NOT, so in this case we MUST have a manual to tell us. Now this manual is called a "Service Manual" or sometimes a "Repair manual" This manual is absolutely vital so much so, that it can be near impossible to do without it. As apart from having "Troubleshooting" step through's, it also has our Voltages. When we measure these Voltages they are 100% EXACT, so IF the Voltage you measure, except for a few rare exceptions, the "Rail" that is NOT at the correct voltage is the one, that the "Fault/Cause" is "ON". Therefore we can now work outwards from the Power Supply, looking for the cause of that problem. Now if the Voltage is Lower than specified, we are invariably looking for a "Short", something has "Faulted" and is "Dragging" the Power Rail down to earth. Now if the "Rail" is "Higher" than the specified Voltage then the fault we are looking for is usually some sort of "Open Circuit" possibly a Diode, or resistor that has changed it's "Value". Now knowing this and knowing that the Power Supply is the FIRST place to start you troubleshooting and repair from. You now have a MUCH better chance of a "Fix". One thing more, DO NOT forget to get your SERVICE MANUAL. for you exact make & model. even if you pay for it, you will be glad you did.
OK if it is shutting down, after that amount of time, of working and then faulting, then it is most definitely a "Thermal" problem, the way we "Find" problems such as this is "Freeze Spray" you use this on each component that is suspected of being the "Culprit" and you will soon,find that errant component. Now also not every fault is a Capacitor, I see many, many people that think, that Capacitors are always the "Culprit" now while that may be true in a few cases, a faulty Electrolytic Cap, or ordinary, Cap goes faulty, this is only a SYMPTOM, something has damaged those caps causing them to "Fail". One MUST always find the root "Cause", otherwise if you just treat, the SYMPTOM, the "Cause" will just make the "Symptom" come back, in short order, as the prime cause still, hasn't been fixed., Now Capacitors hate AC ripple, or Over Voltage. Thats it. Oh.. and Heat, if these Capacitors, are too close to a Heat Source, then thats a prime cause of failure. Resistors, hardly ever go faulty,and if they do, it is generally obvious. However it doesn't hurt to check values with our Multimeter. Remember though resistors are made, with up to 20% tolerance from stated value, as such, are not too critical, unless in Timing circuits etc. Always check, the Values, of resistors, as with any other component, with the power OFF. Now Diodes especially "Zener Diode", are another thing to check, those and ordinary "Signal Diode" should always be suspect. next we have Transistors and IC's. The Transistors MUST ALL be checked to see if they have a good, "Junction" this is done, with our meter set to "Diode Test" and usually are about 0.6 to 0.7. With IC's you must check, voltage levels, or Logic Levels, going in and out, have a look at the circuit diagram, and it will tell you what they should be. It is a good idea to always measure the Power Supply voltages, see if a "Rail" is Low, that will be because some component has gone somewhat or all short circuit, to Earth, now, if the "Rail" is Higher, suspect an "Open Circuit" component, like a Diode, or Transistor. The voltages expressed in the manual are spot on, ANY variation MUST be investigated. I have been doing all this for over 30 years now, and I do indeed wish, we could have a set of "Symptoms" and be ables to say.. "Oh that;s the so-in-so and replace this" however unfortunately this although does happen, most "Symptoms" can have literally tens, of "Causes" all often "Interlinked" One simply has to do a methodical troubleshooting procedure, and always think, "are my Voltages Correct" as this is how, you Fix the problem, by making them so. Keep up the good work. If that link above doesn't furnish a Service manual, it is imperative you get one, even if you must pay for it. It will pay for itself in about 2 mins.

Sep 27, 2011 | Mitsubishi WS-65809 65" Rear Projection...

8 Answers

Hitachi 50UX26B no picture no sound


The deflection board needs replaced.

Dec 05, 2007 | Televison & Video

Tip

How to troubleshoot a power supply board.


After a power surge or thunder storm your TV, DVD, Amplifier or anything with a power supply will not turn on or partially turns on with errors. Your unit may also be many years old and has quit while operating or after shutdown it would not turn on.

If this is the circumstances of your unit you need to first unplug the unit from the mains for safety and remove the cover(s) or back if a TV to access the power supply board.

You will no doubt need to do some sodering so see my tip at http://www.fixya.com/support/r9091711-step_step_procedures_soldering for help with soldering.
.
The first thing you should check is the fuse although with switch mode power supplies you do not find blown fuses very often these days. Using a DMM set to the ohms range (preferably continuity check) check for an open fuse. If there is continuity the fuse is good. If the meter reads a high resistance the fuse is open and needs replaced. Always replace with the exact kind and size (amps) of fuse you take out. Generally these days the fuse rating is marked on the circuit board near the fuse.

Restore power to the unit and try turning it on. If your replacement fuse blows you have a short somewhere in the system. Any boards which will not affect the unit turning on should be disconnected and the fuse replaced and try to power it on again. If the fuse does not blow the problem is in one of the circuit boards which are not hooked up to the power supply. If the fuse blows the problem is in any boards still connected or the power supply.

To troubleshoot the power supply look for any charred or burned components. Look at the electrolytic capacitors to see if the ends are bulging. If they are all the electrolytics should be replaced. Electrolytic capacitors look like small cans, usually different colors but they could be black. They will be marked in microfarads and have a dc voltage rating. They should only be replaced with exact units, same values for both parts of the rating. Also they have a polarity and must be installed the same way they are taken out. The negative terminal is marked on the board and on the device.

If all the capacitors look ok or you replace them all (they are cheap) continue checking all diodes for shorts or opens. Out of the circuit a diode should read high resistance one way and when the leads are reversed you should read about 400 to 800 ohms. This is showing a good part. The DMM should have a diode check setting. It is the location with the symble of a diode beside the position. Diodes can usually be checked in circuit to determine a ball park estimate of whether they have a problem. Remove any which seem suspect and check them out of circuit. Make sure they are reinstalled correctly. They have a polarity also. Line the symble on the device up with the one on the circuit board.

After the electrolytic capacitors and diodes all the transistors (mainly power) should be checked for shorts. If they are shorted you will find them in circuit. Any suspicious units can be removed and tested with a DMM. Testing is done similar to a diode except there are two junctions to test. You should have low resistance between two different sets of leads and high resistance between all others (out of circuit only).

The only things left to check are the resistors. The easiest way to test them is with the meter on diode check make sure they are not in a dead short. Some will be low enough resistance they should test as a short.
They should be marked with the values. Resistors with a high resistance can be tested by changing the range or use auto range.

Any parts can be purchased at http://www.encompass.com or http://www.mcmelectronicsinc.com or http://www.mouser.com .

If all the components check out your power supply is ok and you need to do the troubleshooting on the remaining boards.

Thanks for using FixYa and for the great rating.

hardrocko

on May 10, 2011 | Televison & Video

1 Answer

No sound, no picture but timer srandby light is


If the stnadby light blinks 9x, there is a leaky diode in the G board(5Volts standby circuit) causing the problem. I don't have the service manual but I remember it's the D6301. To make it sure check all 8 diodes including the one in zero detection circuit(all in G board). Hope this helps :)

Dec 25, 2009 | Sony KP-46WT520 46" Rear Projection...

1 Answer

Please help!!!!!!!!!!!!!!!


Good Day;

It sounds like you may problems in the TV's circuits, but try resetting first by unplugging TV from power source. If no fix try these areas of concern:

1. SHUTDOWN CAN BE CAUSED BY NO VERTICAL DEFLECTION. SINCE THE VERTICAL CIRCUIT IS POWERED BY THE SWITCHED POWER SUPPLY THE UNIT MUST BE TURNED ON TO TROUBLESHOOT THE CIRCUIT. THIS CAN BE ACCOMPLISHED BY TEMPORARILY DISCONNECTING THE VERTICAL INPUT TO THE X-PROTECT CIRCUIT. ** TO PREVENT DAMAGE TO THE CRT'S YOU MUST UNPLUG THE CRT PCB'S. ** TO DEFEAT THE X-PROTECT CIRCUIT, UNSOLDER D4A1 LOCATED OFF THE COLLECTOR OF Q4A1. IF THE UNIT POWERS ON AT THIS POINT, YOU HAVE CONFIRMED A VERTICAL FAILURE AS THE CAUSE FOR SHUTDOWN. ** D4A1 MUST BE REINSTALLED IN CIRCUIT TO PREVENT CRT DAMAGE. ** 2.CHECK PIN 1 OF IC401 FOR 10.7VDC. IF LOW OR MISSING CHECK FOR SHORTED D4000 LOCATED OFF PIN 1. (PCB-MAIN) D4000 PART #264P487030 3. CHECK PIN 8 OF IC401 FOR 27.7VDC. IF MISSING CHECK FOR OPEN D955 AND L961 AT S1 TERMINAL OF T902. (PCB-POWER) D955 PART #264P102040 L961 PART #411P012010 4. CHECK FOR DEFECTIVE IC401. IC401 PART #272P239040, OR INSTALL PT# IC-401, THIS KIT CONTAINS CAPACITOR C920, D4000 AND IC401. BE SURE TO MOUNT C920 ON FOIL SIDE OF PCB. 5. EXCESSIVE 130V SUPPLY. CHECK C911 47 UFD 100 V AND C914 47 UFD 50 V, IN THE IC900 CIRCUIT. Good Luck, big IRISH.

Sep 26, 2008 | Mitsubishi Televison & Video

1 Answer

Model vs-4543 mitsubishi tv


Good Day;

One of these may be your problem:

1. SHUTDOWN CAN BE CAUSED BY NO VERTICAL DEFLECTION. SINCE THE VERTICAL CIRCUIT IS POWERED BY THE SWITCHED POWER SUPPLY THE UNIT MUST BE TURNED ON TO TROUBLESHOOT THE CIRCUIT. THIS CAN BE ACCOMPLISHED BY TEMPORARILY DISCONNECTING THE VERTICAL INPUT TO THE X-PROTECT CIRCUIT. ** TO PREVENT DAMAGE TO THE CRT'S YOU MUST UNPLUG THE CRT PCB'S. ** TO DEFEAT THE X-PROTECT CIRCUIT, UNSOLDER D4A1 LOCATED OFF THE COLLECTOR OF Q4A1. IF THE UNIT POWERS ON AT THIS POINT, YOU HAVE CONFIRMED A VERTICAL FAILURE AS THE CAUSE FOR SHUTDOWN. ** D4A1 MUST BE REINSTALLED IN CIRCUIT TO PREVENT CRT DAMAGE. ** 2.CHECK PIN 1 OF IC401 FOR 10.7VDC. IF LOW OR MISSING CHECK FOR SHORTED D4000 LOCATED OFF PIN 1. (PCB-MAIN) D4000 PART #264P487030 3. CHECK PIN 8 OF IC401 FOR 27.7VDC. IF MISSING CHECK FOR OPEN D955 AND L961 AT S1 TERMINAL OF T902. (PCB-POWER) D955 PART #264P102040 L961 PART #411P012010 4. CHECK FOR DEFECTIVE IC401. IC401 PART #272P239040, OR INSTALL PT# IC-401, THIS KIT CONTAINS CAPACITOR C920, D4000 AND IC401. BE SURE TO MOUNT C920 ON FOIL SIDE OF PCB. 5. EXCESSIVE 130V SUPPLY. CHECK C911 47 UFD 100 V AND C914 47 UFD 50 V, IN THE IC900 CIRCUIT. Good Luck, big IRISH.

Sep 14, 2008 | Mitsubishi VS-45607 45" Rear Projection...

1 Answer

VS-5061 -- BLACK SCREEN


Good Day, petterk;
Try resetting TV by unplugging from the A/C outlet for3 to5 minutes. This a 1994 Model, you can't new boards from Mit's. Try this:
1). CHECK FOR 1200 VDC AT PIN 1 OF CONNECTOR "DK". IF LOW OR MISSING CHECK R5D9 100 OHM 1/2 OFF PIN 1 OF THE FLYBACK ON THE MAIN PCB. 2). CHECK IC401 PIN 8 FOR 28 VDC IF MISSING CHECK R510 1.2 OHM 1/2 W OFF PIN 5 OF THE FLYBACK. IF OPEN IC401 PART # 272P239050 MAY BE SHORTED. BOTH ARE ON THE MAIN PCB. 3). CHECK FOR SHORTED OR LEAKY Q2H0, IF BAD APPLY FOLLOWING CIRCUIT CHANGE TO CORRECT. ON FOIL SIDE OF PCB-SIGNAL, SOLDER A 1S2471 DIODE CATHODE TO BASE OF Q2H0 AND ANODE TO EMITTER. LOCATED ON PCB-SIGNAL AT IC201 PIN 2. PT # 264P045040 AND REPLACE Q2H0 PART # 260P559030. 4). CHECK C2H1 100 UFD 35 V C2H2 1 UFD 50 V AND C2H3 47 UFD 35 V OFF OF Q2H1 IN THE SPOT KILLER CIRCUIT ON THE SIGNAL PCB. Good Luck, big IRISH. PS: or call for service, Cost average repair about $500.00, you do the math maybe it's time for a new TV. G.L.

Aug 16, 2008 | Mitsubishi VS-50605 50" Rear Projection...

1 Answer

Convergence Issue 4 JVC AV-54WP74


I was trying to be as clear as possible, sorry. There are several resistors, both in the youke return circuit and feed circuit for the amps that should be checked with a digital or analog meter to see if they have changed in value or have opened as a result of the amp failure. If you've never tested a resistor before then I would strongly suggest having this repair done by a shop. There are several types of resistors, the ones you'll encounter here are a flameproof resistor 1 or 2 watt design respectively.
If you're attempting this you'll need a good analog or preferrably a digital meter with an ohms readout setting. Meter across the resistor and the value of the resistor should not be more than 10% of the rated value. If you read infinity you can assume the resistor is open and clearly should be replaced.
If any of this isn't clear enough then I STRONGLY suggest having a qualified technician do the repair... These are common repairs and if you lack any of the necessary testing or soldering skills you could make matter even worse...
Bill

Mar 29, 2008 | JVC AV-56WP74 56" Rear Projection...

1 Answer

TV problem


Over Current Protection
Pin 1 of IC951 is also the Over Current Protect input.
The internal FET.s ground return is at pin 2 of
the IC. The voltage drop across R955 and R956
indicates the FET.s current, and is coupled through
R953 to pin 1 of the IC. The Over Current Protect
circuit is activated if the voltage at pin 1 of the IC
exceeds 1.35 volts.
Stabilization and rough regulation are provided by
feedback from pin 3 of T951 to pin 1 of the IC. Fine
regulation feedback is from a secondary supply,
through the Photo Coupler, PC951, to pin 1 of IC951.
Its possible that Diode D953 is leaky allowing the voltage to rise on pin 1 of the IC

Feb 23, 2008 | Mitsubishi VS-50605 50" Rear Projection...

3 Answers

TV Turns off on its own ?


You can check the board where the components are mounted and resolder any that look bad. a brief power outages may cause the TV to turn off on its own. If you are using a surge protector, try connecting the set directly to the wall outlet. In your case it could caused by a blown fuse, a leaky diodes or a bad solder joint at the horizontal drive transformer. all can be replaced at a local electronic or hardware store and they're easy to replace If this does not correct the problem, you may need to have your TV serviced.

Dec 21, 2005 | Panasonic PT-53WX42 53" Rear Projection...

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