Help fixing Mitsubishi TV model CK35304
Hi guys,
Need help to repair Mitsubishi console TV model CK35304. (36-inch, manuf. date 1994). Approx a month ago, when you would turn on the TV each day for the first time, the top of the screen would be shrunk down a few inches. As TV warmed up, the screen would return to normal. Color and clarity of picture has been excellent throughout. The other day, turned it on, just get a line thru the middle of the tube. So, whatever was going bad, has definitely gone bad. I do not have TV repair experience, but I have experience repairing other high-voltage items, such as many Tube Guitar Amps, antique radios, PC's, and even rebuilt a Video Game monitor once (installed a capacitor kit). So I am familiar with the voltages involved. I talked with a friend of mine who repairs TV (lives several hours away from me...), and while he is hesitate to tell me a lot (he never tells the secrets of the trade, so to speak...), he said that this a typical problem with Mitsubishi TVs, and that the problem is probably in the Vertical output circuit, then said 'maybe 5 capacitors, probably a chip, and maybe a fuse'. Here are some photos of the boards inside the set: (mainboard) http://mysite.verizon.net/cowman136/tv1.jpg (closeup of area that may be the problem...) http://mysite.verizon.net/cowman136/tv2.jpg (power supply board) http://mysite.verizon.net/cowman136/tv3.jpg You guys can tell me whether my friends general advice is accurate or not. For starters, I have proceeded assuming his advice was good, and did some searches to try to narrow down what I am looking for. Doing some Google searches based upon part numbers on the transistors that I see on the mainboard (picture "tv2.jpg" above) , I found that TA8427K is apparently my Vertical Deflector chip, that C2073 is apparently my Vertical Output chip. In this circuit, I see the following components (and checked them in-circuit, where noted: - fuse (checks good) - 15K ohm 3 watt resis. - checks good, approx 14K ohms in circuit - 4700uF at 10V cap - did not test - 2.7 ohm resistor - good - 2700 ohm resis - good - red capacitor approx 1 inch size with numbers (2A : 335K S) - value unknown, not tested - resistor with bands of "yellow - purple - gold - gold" - tests approx 4 ohms. My photo tv1.jpg above highlights this area of the board. I do not see any visibly burned components or exploded/leaking caps. Assistance is MUCH appreciated. I really need to fix this myself, as cash is very tight. I do not mind installing a few "extra" parts, shotgun approach is fine. Also, advice as to where is best to buy the parts (the IC's, as I probably have the caps & resistors) will be appreciated. THANKS. BJ |
Help fixing Mitsubishi TV model CK35304
In data Sun, 18 Jun 2006 05:41:26 +0200, ha scritto:
Approx a month ago, when you would turn on the TV each day for the first time, the top of the screen would be shrunk down a few inches. As TV warmed up, the screen would return to normal. Color and clarity of picture has been excellent throughout. You have a vertical problem. The other day, turned it on, just get a line thru the middle of the tube. So, whatever was going bad, has definitely gone bad. I do not have TV repair experience, but I have experience repairing other high-voltage items, such as many Tube Guitar Amps, antique radios, PC's, and even rebuilt a Video Game monitor once (installed a capacitor kit). So I am familiar with the voltages involved. Hantarex ? ;) I talked with a friend of mine who repairs TV (lives several hours away from me...), and while he is hesitate to tell me a lot (he never tells the secrets of the trade, so to speak...), he said that this a typical problem with Mitsubishi TVs, and that the problem is probably in the Vertical output circuit, then said 'maybe 5 capacitors, probably a chip, and maybe a fuse'. Here are some photos of the boards inside the set: (mainboard) http://mysite.verizon.net/cowman136/tv1.jpg (closeup of area that may be the problem...) http://mysite.verizon.net/cowman136/tv2.jpg (power supply board) http://mysite.verizon.net/cowman136/tv3.jpg You guys can tell me whether my friends general advice is accurate or not. For starters, I have proceeded assuming his advice was good, and did some searches to try to narrow down what I am looking for. Doing some Google searches based upon part numbers on the transistors that I see on the mainboard (picture "tv2.jpg" above) , I found that TA8427K is apparently my Vertical Deflector chip, that C2073 is apparently my Vertical Output chip. In this circuit, I see the following components (and checked them in-circuit, where noted: - fuse (checks good) - 15K ohm 3 watt resis. - checks good, approx 14K ohms in circuit - 4700uF at 10V cap - did not test - 2.7 ohm resistor - good - 2700 ohm resis - good - red capacitor approx 1 inch size with numbers (2A : 335K S) - value unknown, not tested - resistor with bands of "yellow - purple - gold - gold" - tests approx 4 ohms. This resistor was good ! (yellow-purple-gold = 4,7 ohm) Changing components without measures isn't a good idea. Start from changing all electrolytic caps in that zone, then My photo tv1.jpg above highlights this area of the board. I do not see any visibly burned components or exploded/leaking caps. Assistance is MUCH appreciated. I really need to fix this myself, as cash is very tight. I do not mind installing a few "extra" parts, shotgun approach is fine. Also, advice as to where is best to buy the parts (the IC's, as I probably have the caps & resistors) will be appreciated. THANKS. BJ -- Inty.Evolution - per email normali e con immagini Jpeg |
Help fixing Mitsubishi TV model CK35304
(closeup of area that may be the problem...) http://mysite.verizon.net/cowman136/tv2.jpg This is the flyback transformer area. If the design has the vertical circuits power supplied by the flyback, then your height shrinkage could be a premature sign the flyback is breaking down, or there could be a problem only in the vertical circuit....changing all capacitors in the vertical circuit is a common solution to certical problems, however the flyback xfmr in that chassis is common fail\, so its of not it be mentioned. |
Help fixing Mitsubishi TV model CK35304
In data Sun, 25 Jun 2006 17:24:49 +0200, default ha scritto:
(closeup of area that may be the problem...) http://mysite.verizon.net/cowman136/tv2.jpg This is the flyback transformer area. If the design has the vertical circuits power supplied by the flyback, then your height shrinkage could be a premature sign the flyback is breaking down, or there could be a problem only in the vertical circuit....changing all capacitors in the vertical circuit is a common solution to certical problems, however the flyback xfmr in that chassis is common fail\, so its of not it be mentioned. MAYBE a blown fuse resistor? -- Inty.Evolution - per email normali e con immagini Jpeg |
Help fixing Mitsubishi TV model CK35304
Hi,
Thanks to `Inty` and `default` for replies. The fuses all check fine, unless I am not seeing all of them. I am familiar with fuse-resistors, too. Update: I changed the 3 electrolytics in the vertical circuits (100mfd at approx 35V), and they did not help. I checked the caps that I removed, and all were close to 100mfd (the weakest tested 88 mfd). Talked to 2 guys (my original source, and another guy that I know who was in the tv sales/service business for many years), and both guys believe that 99% likelihood that the problem is defective TA8427K vertical deflector chip. Both guys said this part goes bad regularly. So I have already unsoldered it, and have ordered a replacement. Cheap solution if it works. Less than $8 including postage for a real Toshiba chip. Should arrive in a few days. If that does not fix it, we'll go from there. The only thing that I wonder about, is that my friend asked me to check whether there is 24V from pin 6 to ground on TA8427K. Well, I got 0, although it was `damn hard` to get a reading in that area of the board while the set was operating. It is possible I was not getting good contact with my meter. Assuming the 0 is accurate, he says that means something else is wrong, although he feels that the chip is probably bad also (which he originally said I should replace). So I Look around on the board, there is not many components in that area. A diode goes directly to pin 6 of TA8427K, and a bunch of other diodes are in the immediate area (all diodes checked normal once I removed the TA8427K), and of course the 100mfd caps (replaced), and a couple mica caps (very unlikely to be defective). There is 1 glass fuse in the area, which is good. He asked me to look for small black square boxes, which he says would be fuses. There is none of them. I can easily identify the components in the area, so I really cannot see any way that I am missing a fuse anywhere. This might be a lot easier with a schematic, but I doubt at this point it would tell me a whole lot. I'll know more once the vertical deflector chip has been replaced. Thanks again. Inty XP wrote: In data Sun, 25 Jun 2006 17:24:49 +0200, default ha scritto: (closeup of area that may be the problem...) http://mysite.verizon.net/cowman136/tv2.jpg This is the flyback transformer area. If the design has the vertical circuits power supplied by the flyback, then your height shrinkage could be a premature sign the flyback is breaking down, or there could be a problem only in the vertical circuit....changing all capacitors in the vertical circuit is a common solution to certical problems, however the flyback xfmr in that chassis is common fail\, so its of not it be mentioned. MAYBE a blown fuse resistor? -- Inty.Evolution - per email normali e con immagini Jpeg |
Help fixing Mitsubishi TV model CK35304
SOLVED by replacing the TA8427K vertical deflector chip. Good as new. Thanks to everyone for their suggestions. |
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