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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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#1
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CTC187 dead
I got this set, friend wants it fixed.
He said the power button is messed up, and it doesnt turn on. well, I seen that it was a ctc187, I know thats not the case. I got the set, and pressed the button, it presses fine. I immidiately thought in my head, since I worked on these before, the 10uf cap in the SMPS primary is gone, fuse is gone, and STK is wasted. thats what I first thought. I took it apart, only to confirm my suspician, the fuse is wasted. I pulled it out, here is the rundown so far: caps look normal, no bloated or exploaded caps like on most of the ones I worked on. The fuse is gone, the HOT is shorted, and 1 of the 2 secondary diodes is shorted. The one that feeds the flyback and associated circuits is shorted. Ok, question. What caused the HOT to blow in the first place? flyback possibly bad? I got another board identical to it, that had a bad STK, and all the power supply caps. Everything was recapped, but the woman said she tossed it, and didnt want it fixed, so I never got the STK, and ended up robbing the caps and the NTSC processor for another set. The HOT and associated circuits are still OK. I wonder if I should just pull the flyback and HOT, with the diodes, and some blue pincussion caps and change them out? any thoughts would be appriciated. ---- Mike |
#2
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CTC187 dead
Simple ring the flyback to find out if it is bad.
Check the horizontal driver transformer solder connections, could also short HOT. Tuner ground problems or corrupted eeprom due to same can also blow HOT. Arcing back crt could also cause failure. Failure in the smps main b+ diode can blow the HOT. Lots of different possibilities, start doing the basic troubleshooting for that type of failure, then continue troubleshooting once unit can be powered up with the main b+ current limited. David |
#3
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CTC187 dead
Make sure the diode that supplies the HOTr is good or bad, if its good the
HOTr is bad , you have to unsolder one or the other, either one could cause the fuse to go. Vince "Mike Bates" wrote in message . .. I got this set, friend wants it fixed. He said the power button is messed up, and it doesnt turn on. well, I seen that it was a ctc187, I know thats not the case. I got the set, and pressed the button, it presses fine. I immidiately thought in my head, since I worked on these before, the 10uf cap in the SMPS primary is gone, fuse is gone, and STK is wasted. thats what I first thought. I took it apart, only to confirm my suspician, the fuse is wasted. I pulled it out, here is the rundown so far: caps look normal, no bloated or exploaded caps like on most of the ones I worked on. The fuse is gone, the HOT is shorted, and 1 of the 2 secondary diodes is shorted. The one that feeds the flyback and associated circuits is shorted. Ok, question. What caused the HOT to blow in the first place? flyback possibly bad? I got another board identical to it, that had a bad STK, and all the power supply caps. Everything was recapped, but the woman said she tossed it, and didnt want it fixed, so I never got the STK, and ended up robbing the caps and the NTSC processor for another set. The HOT and associated circuits are still OK. I wonder if I should just pull the flyback and HOT, with the diodes, and some blue pincussion caps and change them out? any thoughts would be appriciated. ---- Mike |
#4
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CTC187 dead
Hi!
I have found that i can be either the diode that fernishes the power to the HOTr or the HOTr.unsolder to check, either one of these or the regulator can take out the fuse. Vince "Mike Bates" wrote in message . .. I got this set, friend wants it fixed. He said the power button is messed up, and it doesnt turn on. well, I seen that it was a ctc187, I know thats not the case. I got the set, and pressed the button, it presses fine. I immidiately thought in my head, since I worked on these before, the 10uf cap in the SMPS primary is gone, fuse is gone, and STK is wasted. thats what I first thought. I took it apart, only to confirm my suspician, the fuse is wasted. I pulled it out, here is the rundown so far: caps look normal, no bloated or exploaded caps like on most of the ones I worked on. The fuse is gone, the HOT is shorted, and 1 of the 2 secondary diodes is shorted. The one that feeds the flyback and associated circuits is shorted. Ok, question. What caused the HOT to blow in the first place? flyback possibly bad? I got another board identical to it, that had a bad STK, and all the power supply caps. Everything was recapped, but the woman said she tossed it, and didnt want it fixed, so I never got the STK, and ended up robbing the caps and the NTSC processor for another set. The HOT and associated circuits are still OK. I wonder if I should just pull the flyback and HOT, with the diodes, and some blue pincussion caps and change them out? any thoughts would be appriciated. ---- Mike |
#5
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CTC187 dead
the HOT is fine, I snipped the diode, and its indeed bad, and that means the
STK is bad, and the 10uf cap in the primary caused it. "Vince" wrote in message ... Hi! I have found that i can be either the diode that fernishes the power to the HOTr or the HOTr.unsolder to check, either one of these or the regulator can take out the fuse. Vince "Mike Bates" wrote in message . .. I got this set, friend wants it fixed. He said the power button is messed up, and it doesnt turn on. well, I seen that it was a ctc187, I know thats not the case. I got the set, and pressed the button, it presses fine. I immidiately thought in my head, since I worked on these before, the 10uf cap in the SMPS primary is gone, fuse is gone, and STK is wasted. thats what I first thought. I took it apart, only to confirm my suspician, the fuse is wasted. I pulled it out, here is the rundown so far: caps look normal, no bloated or exploaded caps like on most of the ones I worked on. The fuse is gone, the HOT is shorted, and 1 of the 2 secondary diodes is shorted. The one that feeds the flyback and associated circuits is shorted. Ok, question. What caused the HOT to blow in the first place? flyback possibly bad? I got another board identical to it, that had a bad STK, and all the power supply caps. Everything was recapped, but the woman said she tossed it, and didnt want it fixed, so I never got the STK, and ended up robbing the caps and the NTSC processor for another set. The HOT and associated circuits are still OK. I wonder if I should just pull the flyback and HOT, with the diodes, and some blue pincussion caps and change them out? any thoughts would be appriciated. ---- Mike |
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