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#1
03-13-2009, 08:08 PM
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1949-50 RCA "U" chassis horizontal osc. problem
Hi:
I have a 1949-50 RCA model TA-129 radio-TV-phono that has horizontal oscillator problems. The oscillator is way off as the set has 3-4 pictures side-by-side. I have recapped the horizontal circuit, checked and rechecked wiring, resistor and capacitor values, etc. I even replaced the oscillator coil with one from a parts set but no difference. Disconnected the sync and no difference. All voltages are correct. Of course I get normal picture when I feed horizontal plate from my B&K Analyst. I have had two friends, both excellent techs, work on it but none of us can figure out what is wrong with this set. Has anyone run into anything like this on an early "U" chassis RCA? Any and all help would be greatly appreciated. Thanks. 
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#2
03-13-2009, 09:07 PM
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The oscillator coil has two sections. One, along with the coupling, cap, determines the frequency. The other is a waveshaping coil.
1. Short the wave shaping coil with a jumper. That's the one with the .01 cap across it. 2. Center the horiz hold control. 3. Adjust the frequency coil for one picture. ( It's the only slug that will do something) 4. Remove the short and set the wave shaping coil for a proper picture. (That's the other slug) 5. Follow the alignment instructions for a final setting. If that does not fix it, let us know what step did not work. Don
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#3
03-17-2009, 02:12 PM
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Hi Don:
I tried that but still can't get less than 2-3 pictures, overlapping and side-by-side. The odd part is the oscillator "squeal" sounds fairly normal. I only have a cheap Radio Shack frequency meter, but when I connected it to the jumpered wave shaping coil the reading fluctuated wildly between 14-17kHz. I don't know fl it is just the cheap meter or if the oscillator is unstable and that is the real problem. I did not replace the filters, could there be AC ripple getting into the circuit and causing the problem? I will have to dig my scope out. Thanks. John
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#4
03-18-2009, 01:18 AM
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It is a possibility. Can you hear the horizontal squesl through the speaker? If so, a sure sign of bad electrolytics somewhere.
Try bypassing the electrolytics for the horizontal B+ supply anyway. Don
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