I have a GE 44 inch rear projection tv 46GW945 the picture has suddenly become concave and it seams as though the collars have seperated
I know this set very well--you are describing a convergence problem and this set is prone to one fairly simple thing going wrong that causes this trouble.
I need to know if you have any knowledge about testing Diodes? The common problem in this set is there is inside ABOVE all the main circuit boards a smaller board held in with 4 screws; there are only a few plugs on the board. This board provides POWER to the convergence circuit.
On the far right side of the board are several small black diodes and TWO LARGER ONES----what usually happens is one of the two large ones shorts----if you locate them you check them like a fuse---if one reads like a fuse it is the bad one---it will have a location number on top of the board under it---give me the location number and I will Try to get you a part number---the diode if it is bad is 85% chance causing the convergence problem---over the years I have seen over 24 of these sets with this trouble.
THESE DIODES ALSO HAVE A GENERIC NUMBER ON THEM.
Let me know if you have questions and I will help you--keep in mind possible differences in Time as I am in California.
SD TECH
The two large diodes are your best hope for a easy fix. Both should read the same on a diode test-I suggest you unsolder one end of each diode and lift them up to get a good test. These sets do not have many convergence problems other than this--they should be close to each other towards the right side of the board--with one end of each unsoldered check them out of circuit with the diode test feature if your meter has it......If they are good--let me know what happens if you go with an original remote into the TECH menu and try to adjust convergence--I hope you find one of the diodes bad--the other possible reasons are not simple---those two diodes are much larger than the others on that board.
On a regular ohmmeter set to 20 k or more you should read about 4 k one way and nothing the other.
If I remember there is also a to220 type transistor on that board--check it also--9 out of 10 times one of the diodes is bad. The only other way to confirm this is with the board back in check voltage on the side of each diode on the output side (towards the right) The way all these sets work is one diode will have the K facing right and the other left--they work with two voltages---placement of the diodes means one voltage will be plus and the other negative.
I will be around for a few hours---lift the diodes and carefully check them---if one has a different reading out of circuit than the other (lower etc) it may be leaky---the voltage check will confirm this--both output voltages should be close except one will read positive and the other should read negative.
SD TECH
The diodes cannot read 3.2 ohms in one direction--that would be a
short--3.2 K or thousand would be acceptable. The other part you are
talking about is a voltage regulator ic. It controls voltage on the board--STK-730-020.
Something you have to keep in mind--when measuring voltage this set like others uses two different grounds--you have to have your ground lead on the meter connected to a ground on the board--do not measure from the main chassis or metal frame around the crts. One is a neutral or earth ground but the one on the board will be from a "Hot" ground. if you measure using the wrong ground you will get wrong readings---
Based on what you have told me the two large diodes are good--you may want to look at the large board on the right side of the main chassis--rows of transistors there with heat sinks--it is the convergence output board and can be removed to examine things on it--These sets did not use Convergence chips like most of the other sets--two rows or more of transistors there perform the same job. They rarely fail; if you remove that board you are going to look for either broken solder joints or any open or burnt resistors---I have only seen two or three with problems on that board but if the board with the diodes is ok you have to look there.
That voltage regulator ic cannot be tested--all you can do is check the voltages on it and see which go to the diodes--if in doubt it is a cheap part and you can replace it to see if it helps.
Look for the STK730-020 CHIP--rca no longer sells them but several places on the net do--cheap part.
SD TECH
×
110 views
Usually answered in minutes!
I believe I found the board you are talking about,there are two plugs and several diodes,I tested the large diodes like a fuse they both read like a open fuse,no continuity,I tested them with diode check on my meter and they both read 42 in one direction one reads 75 and one reads 101 in the other direction (I dont know if this is significant but I thought I would let you decide)
thanks
first I want to say, I appreciate your help. I removed one end of each of the diodes and tested them. they were blocking in one direction, 3.2 ohms in the other direction (both were approximately the same). I have tested transistors that have been clearly marked (I am an elec forklift mechanic)but I have no idea how to test what I believe to be the transistor on this board(it is attached to an alluminum heatsink and has 11 pins the number on the board at its location is U19700.)
I forgot to include I checked the voltages before I removed the diodes from the circuit both read 61 volts
×