daletheone
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Mar 30, 2003, 5:53 PM
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RCA 32" pincushion problem
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Hi Experts (expert = a drip under pressure), I have an RCA 32" (ctc187cn3) that has a pincushion problem. Measured the voltages on the pincushion transistor buffer and amp (Q4801 and Q4802) and found that the bias on the emitter is low - about 7.9V. It should be ~13.5V and this low value is causing these transistors to be in cutoff (since their base is about 13V and these are PNPs). The 13.5V is supposed to be generated after the HOT (CR4401, CR4402, etc.) and through the yoke. The 140V from supply looks good but collector of HOT should read 140V but in fact reads 158V. The pincushion problem went away temporarily and the HOT collector still read 158V so I don't think the high reading is the problem. The cathode of CR4401 reads 62.0V and the anode reads 7.94V (this is the bias that is going to the pincushion buffer and amp that should be about 13V). The R4401 in parallel with CR4401 reads 14.8K (should be 15K so that looks okay). The Vforward of CR4401 is 0.44V which seem okay. Can't figure out why the voltage is too low. Any clues? Thanks!
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