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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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Question on CTC187 was blown HOT.
Hi all,
F27634xxxxx, STK730 SMPS, CTC187BJ. I decided to use bulb 135W (two bulbs) in series on the AC input in place of fuse to prevent horizontal transistor blown again just in case. Glad I did! When horizontal circuit starts up it gave fraction of a second for HV and horizontal pulses then mess up instantly with high current draw. Cycling by the visual of strobing light from bulbs. Checked: flyback transformer, pin circuit, redid tuner & micro grounds (this is one of rare chassis using COPPER box for tuner! Prior to this, I have done so many tuner jobs and it is zinc from my experience with zinc metal & soldering), have HV as well. Had scope on the base of HOT, I got good pulses for a fraction of a second (several cycles) just once strobing kicks off once waveform distorted with high frequency noise in off cycle times at that point bulb lits up and chassis loses power then get power back again, loses power again as it tries to run horizontal. Cycle goes on. Checked the flyback transformer outputs with scope as well and can get nice good waveforms several cycles for fraction of second then distorts, after that point just the bad waveforms as long as bulb strobes. Had to unplug then plug again to get that clean fraction of second waveforms. Makes sense? Cheers, Wizard |
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