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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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CTC 169 flyback questions and notes fly p/n# 232191 Update
Got a new flyback from Union and installed it. Everything seemed ok, but I noticed that the HV regulator seemed not to be working. The problem turned out to be a shorted 820pf capacitor on the HV splitter voltage sensing circuit that is mounted on on the splitter itself. Thanks for all the tips folks --DM-- "Dave Moore" wrote in message ... I just fixed an early Family 1 version PTV for a friend of mine. What a nightmare, fixed SMPS, replaced 7 bad xstrs and numerous weak caps in convergence power section, repaired no video, and no sound problem ( TV from hell:-),thought all was ok, then the dang thing just quit working. After defeating/bypassing a number of the shutdown circuits I got it to run for about 5 seconds. Just long enough to notice that the HOT was getting hot. So, I figured that the flyback was probably bad. Out of desperation to verify this, I took a flyback off of a 169 chassi for a 31" TV. Ok, here's where it gets interesting. After studying the situation a bit, I determined that the black wire for the PTV flyback and the same black wire for the 31" TV are not the same. On the PTV, this black wire is the other end of the CRT anode winding, and not the focus tap like it is on the flyback for the 31" set. So, I put the 31" flyback in the PTV, only I didn't connect the black wire to the HV regulator board. Instead I cut the ground traces going to one of the pins on the flyback which I had determined was the other end of the HV anode winding for this 31" flyback and soldered my own "black wire" to this pin and connected it to the HV regulator board. Well, the PTV came up and worked beautifully. All PS voltages measured within specs and the HV measured 28K. a little low I think but the picture looked fine. Well, I ran it for about 8 hours and started to work on adjusting the convergence. While I was working on the convergence, the set went *POP* and shut off and immediately came back on. Then about 5 minutes later it did the same. Then after that. it never did this again for about 3 hours. After I finished the convergence I shut her down and told my friend that he could give it a go if he wanted to, but I didn't really trust it. Sure enough, when he came to get it, we turned it on, it came up and went *POP*,, for good this time. Ok, I am about to order a new flyback from MCM for $29. I just stumbled on a thread in the freelists group where some techs are discussing some problems with the replacement parts for this set. Also I found an article by JURB in the SER Google archives about this same issue. So, 2 questions,,, anyone have any suggestions about why 2 flybacks crapped out when everything seemed to be ok? I realize that the 31" flyback may simply not have HV diodes in it sufficient to handle the beam current in the PTV, but I really have some doubts as to whether this was the reason that the origional flyback checked out. 2'nd question,, anyone had any problems using the sub part 232191 from MCM ? Thanks =^^=DM |
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