Mitsubishi Projection TV--- Trouble free since purchase in 1995.
Recently started showing slight jitter in magnitude of vertical deflection for several minutes after powering up. This jitter evidences itself as intermittent switching between full vertical raster size and approximately 5% reduction in amount of vertical raster size.
This jitter disappears after the TV has been operating for duration of 5 to 6 minutes.
If this is indicative of a pending major failure, I would like to take preventive steps to correct the potential source of the problem.
Have been unable to obtain the VS-5074 Service Manual.
Does anyone on line have suggestions as to whether the trouble symptoms might be due to improperly set power supply voltage or other settings? If so, can anyone provide directions/instructions on checkpoints and adjustment settings location.
I have same problem, but now it takes 6 hours to disappear. Any help?
CharlseV and Jackmac, These problems in Mitsubishi TV sets are generally cause by leaky, or capacitors that are drying out. They mostly are located in the vertical sweep section of the TV set, or the sweep power supply circuit that supply's the b+ to the vertical IC or the vertical drive circuit. The way to troubleshoot this would be of course locate a Service manual, as I did look but have not found one yet, and use an ESR capacitor checker. This type of capacitor checker meter will check capacitors fast and easy in the circuit and without unsoldering them. When I go over a TV set because I suspect more then one leaky or dryed capacitor, I simply check and replace as I go along and doing this will most of the time, fix almost every little problem that is happening in the TV set. If you do not have a meter such as this, you will have to painstackenly unsolder each capacitor and check them with capacitor checker, and those do not really do a good job of doing so. It would be probably less money for you to find all of the capacitor values ariound the vertical sweep IC, and in the power supply feeds to the vertical circuit, and replace them making sure you do pay close attention to the way they come out and go back into the printed circuit boards. One mistake and POW a very unforgiving TV set. This may cost you a little and you may not find all of the bad capacitors this way. I would suggest that you get a trained tech, with all the proper equipment to assist you in this repair. Good Luck and please let us know how you both made out with this repair.
Thanks!
Larry, Thanks from this end also.
Will check into possible acquisition of the capacitor checker. The problem is still intermittent but getting more severe as time goes by.
I am still looking for the Service Manual, but have had no luck so far.
Thanks again,
Charles V
Status report on this continuing problem.From performing several Google searches re this problem, I obtained numerous reports pointing towards the PIP module as a likely source of this vertical jitter problem. Apparently, on early versions of this TV set, this card was plagued with leaky capacitor problems.I located this card and removed it for a close physical inspection. It was in excellent physical condition, with no evidence of any leaky capacitors. I was able to make what is called a "PIP Bypass" to operate the TV with this card removed from the set. Unfortunately, the vertical jitter was still present.Without access to a service manual, I've been unable to identify which card or module contains the vertical circuitry, so as to be able to remove the card or module for a close physical inspection ---- and to be able to replace any apparent problem capacitors.If anyone on site can give me some help in locating where this card resides on the chassis, it would be greatly appreciated.TIA,Charles V
Charles, Do you see a chassis number? I may have a simular model with same chassis
Larry,
Thanks much for the unbelievable fast response.
The only label that I can find is on the back of the high voltage plastic protective enclocure. It just shows the Mitsubishi Model # VS-5074 and a serial number 003896.
Hope this is of help.
Thanks again,
Charles
Larry,
I've found another label on the back of the front speaker panel. Cannot read the fine print, but there is a large numeral 56080 imprinted. It could be upside down, and if so, would be 08095.
Cannot get a magnifying glass positioned close enough to read the fine print, as to whether it is a chassis identification label. It would seem that the obvious place for a chassis label would be on the chassis itself (where the Model No. VS-5074 label is located on the high voltage plastic protective cover).
Charles V
Another Update on Vertical Jitter Problem on Mitsubishi VS-704
Moving the TV Cabinet forward about 24", over tile floor, seemingly has temporarily corrected the problem.
Before so moving the cabinet, the problem had become much more severe, sometimes resulting in complete loss of raster display for periods of several minutes.
This change in symptoms (resulting from cabinet being slightly jarred by movement over tile floor) may point to a faulty connector connection or faulty solder connection on one of the circuit boards.
Now comes the problem of localizing which board contains the faulty connector connection and/or faulty solder connection.
Larry,
Re Chassis Number. Although I still have not visually located the Chassis Number label on my set, I have come across a reference specifying that the Mitsubishi VS-5073 uses Chassis V13B. My user manual is labeled VS-5073/VS-5074 so I suspect both models use the same chassis.
My set was jitter free all day long yesterday and most of today. After being on all morning and through early afternoon today, with no jitter, I turned it off for several hours. When turned back on this evening, the jitter reappeared (as severe as has been previously encountered), with visible off-sets of the individual RGB raster traces followed by complete loss of display for several minutes. After switching power on and off several times, the display came back on with a normal (jitter free) display.
Still need to find which board (and its location on chassis) contains the vertical sweep circuitry.
Does the fact that the jitter problem I'm encountering only occurs for a short time after power start up more likely point to a faulty solder connection or to a defective electrolytic condenser?
If the TV is left on continuously, it is absolutely jitter-free.
Would welcome input from anyone on site.
TIA,
Charles V
Believe I've found the problem and made a temporary fix.
By tapping on the PCB Main circut board, I found the jitter was localized to flat stock heat sink, to which the IC401 (Vertical Out) is attached by a phillips-head/threaded screw. By applying small amount of pressure to this U-shaped heat sink, the jitter was eliminated.
Have made temporary fix by wedging a strip of hi-density foam between the U-shaped heat sink and another adjacent similar heat sink assembly. This applies sufficient pressure to the IC401's heat sink so that tapping it no longer actuates the jitter. Without pressure being applied to this heat sink, any tapping onto it would create lots of jitter and off-set of the individual RBG video display components (major convergence off-set)
A permanent fix will require access to bottom/trace side of the PCB Main. It's not obvious how the U-shaped heat sink is connected to the bottom/trace side and ground-plane of the PCB. There are tabs along the bottom edge of the heat sink protruding through slots in the surface of the PCB Main board. The heat sink appears to be made of aluminum stock and normally would not be readily solderable to the PCB ground-plane, so is probably relying on pressure contact connection .
Before attempting the removal of the main chassis to which the PCB Main is attached for making a permanent fix, I will see how the temporary fix holds up. Access to the circuitry for the tapping/trouble shooting was made by removing the speaker panel, which gave ready access for making the temporary fix. Removal of the main chassis assembly is a more formidable task.
Any suggestions relative to the best procedure for removal of the main chassis for applying the permanent fix would be appreciated. I have been able to obtain a copy of the VS-5074 Service Manual but it doesn't provide much guidance for this next task.
Charles V
Thanks to now having obtained the Service Manual, I have found how convenient it is to access the dynamic convergence controls and have made minor dynamic convergence touch up adjustments. The display now looks as good as when new.
The temporary fix worked flawlessly for a year---- until I was setting up a new remote control and had to turn the TV on & off several times in the process of finding the proper remote contol code number to match the TV's code.
During this process, the TV went blank with no picture. The audio is still present when the set is turned on, but only a single horizontal line sometimes appears accross the upper part of the display when the power is reapplied after being turned off momentarily.
This would seem to indicate the high voltage is present but no vertical scan. I suspect this could point to defective vertical output IC, which is mounted to the flat stock heat sink that was the source of the intermittent vertical jitter, the original problem a year ago.
My problem now is how to remove the PCB Main board assembly. The Service Manual contains only a brief paragraph detailing the removal of a couple of retaining screws. Nothing about removing the high voltage cable bundle to the three projection CRTs nor other wiring disconnects. some of the other wiring cables have enough slack to slide out the PCB Main assembly but not enough to turn the main assembly over to gain access to the underside of the circuit board for desoldering the suspect Vertical Output IC.
Any info on best way to accomplish this would be appreciated.
Obtained Service Manual from MITSUBISHI DIGITAL ELECTRONICS AMERICA, INC.
PARTS DEPARTMENT
1001 CHERRY DRIVE, SUITE 2
BRASELTON, GEORGIA 30517
PHONE: (800) 553-7278
FAX: (800) 825-6655
Charlesv, While sliding back the chassis, pay close attention to the wires that you are pulling on and some you may need to unplug. To the best of my memory though, I think most of the wires can be untied or unclipped with wire ties or clips.
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