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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Sony 53XBR35 Pincushion/convergence problem
One special note. When you remove the old convergence ic's, completely
remove the old heatsink compound and reapply an air tight thin coating of heatsink compound to the new ic's. Make sure they are firmly attached to the heatsinks. Be very careful not to damage or overheat the circuit boards when removing the old parts. Sony boards tend to be easily damaged and lift the circuit traces. David Mirek Chmiel wrote in message news:3fb80cf5$0$9745$afc38c87@... This TV is about 7 years old. About 2 years ago it had similar problem. At that time, we had a local company fix it. On the bill, they stated replacement of one transistor. Unfortunately, I don't have that info anymore to specify which one. This time, I did google search on this problem and found much useful info. The purpose for this email is to further pinpoint the root cause of my problem. For a couple of weeks, while TV was warming up, I did notice short picture problems. For a fraction of a second the picture would be distorted. Because of a short duration, I couldn't tell exactly what the distortion was. Yesterday my family told me, that there was a problem with TV. I couldn't immediately check it out so can't say, if this was instantaneous or not. When I finally looked at it, I saw a pincushion problem. Today I replaced F902 fuse and for a short while, everything is OK. After few seconds (10-20) the red color fails and, on the convergence screen, it moves off half of the screen to the left. Blue is still pretty good. At this time, I can smell a burning component and I turn the TV off. After checking for hot components, I did notice, that the top STK is hot. At this time, I'll follow the advice from David Kuhajda from 2000/06/09 for a Sony RPTV KP-41EXR96 : If the fuse is blowing, even intermittently you need to Replace both STK convergence output ic's, check all the low ohm resistors in the convergence output circuit. Then check the vertical output ic and the 2 small fusible resistor to the vertical ic, typically when one of the convergence ic's starts to go it opens up the fuse, which unbalances the voltage to the vertical ic, if it is not bad now, it will likely fail within the next month. I had 3 in a row that got 2 convergence ic's and a fuse, only to have the vertical ic fail within a month later, so we now replace the vertical ic whenever either the +15v or -15v fuse opens up, order the ic by number from MCM or other generic parts distributor, as well as the stk outputs, Sony wants way too much for these high volume parts, and they buy them from the other manufacture as well. David If anyone has any additional info/advice please let me know. Thank you. Mirek |
#2
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Sony 53XBR35 Pincushion/convergence problem
You are still looking at the same voltages driving the convergence ic's.
Those should be replaced regardless. The vertical ic is not a concern if you are not worried about the chance of having to open the set up again and replace it later. It is not like you will have to make another trip out to fix the set a second time. Sony models use almost identical internal electronic chassis designs for any given run. I would have to check but since your set does fall at the same vintage, 7 years or so, as the other Sony chassis that had the same problems, I would be suspect of the vertical output ic. To be sure is the signal board with the fuses and vertical output ic mounted vertically on the right side of the set (when looking from the rear) with the convergence board mounted towards the front of the set? David Mirek Chmiel wrote in message news:3fb82c40$0$9746$afc38c87@... Thanks David. Since you were dealing with different TV before (RPTV KP-41EXR96 ), does the rest of your advise apply to my model. At this time, I don't have a schematic for this TV. So far I verified, that all low ohm resistors are OK. Should I replaced vertical ICs? Mirek "David" wrote in message ... One special note. When you remove the old convergence ic's, completely remove the old heatsink compound and reapply an air tight thin coating of heatsink compound to the new ic's. Make sure they are firmly attached to the heatsinks. Be very careful not to damage or overheat the circuit boards when removing the old parts. Sony boards tend to be easily damaged and lift the circuit traces. David Mirek Chmiel wrote in message news:3fb80cf5$0$9745$afc38c87@... This TV is about 7 years old. About 2 years ago it had similar problem. At that time, we had a local company fix it. On the bill, they stated replacement of one transistor. Unfortunately, I don't have that info anymore to specify which one. This time, I did google search on this problem and found much useful info. The purpose for this email is to further pinpoint the root cause of my problem. For a couple of weeks, while TV was warming up, I did notice short picture problems. For a fraction of a second the picture would be distorted. Because of a short duration, I couldn't tell exactly what the distortion was. Yesterday my family told me, that there was a problem with TV. I couldn't immediately check it out so can't say, if this was instantaneous or not. When I finally looked at it, I saw a pincushion problem. Today I replaced F902 fuse and for a short while, everything is OK. After few seconds (10-20) the red color fails and, on the convergence screen, it moves off half of the screen to the left. Blue is still pretty good. At this time, I can smell a burning component and I turn the TV off. After checking for hot components, I did notice, that the top STK is hot. At this time, I'll follow the advice from David Kuhajda from 2000/06/09 for a Sony RPTV KP-41EXR96 : If the fuse is blowing, even intermittently you need to Replace both STK convergence output ic's, check all the low ohm resistors in the convergence output circuit. Then check the vertical output ic and the 2 small fusible resistor to the vertical ic, typically when one of the convergence ic's starts to go it opens up the fuse, which unbalances the voltage to the vertical ic, if it is not bad now, it will likely fail within the next month. I had 3 in a row that got 2 convergence ic's and a fuse, only to have the vertical ic fail within a month later, so we now replace the vertical ic whenever either the +15v or -15v fuse opens up, order the ic by number from MCM or other generic parts distributor, as well as the stk outputs, Sony wants way too much for these high volume parts, and they buy them from the other manufacture as well. David If anyone has any additional info/advice please let me know. Thank you. Mirek |
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