Quote:
Originally Posted by radio nut
My CBS-Colombia tv has a vertical chassis and a metal cabinet.I thought my speaker was blown but now I am begining to wonder about it. When I first worked on this set trying to get it to run at all I had the speaker hooked up sitting on the bench. It sounded fine.Now that it is in the cabinet it sounds blown, any bass at all -even deep voices and it is distorted. The chassis should be isolated from the cabinet by caps and resistors, could that assembly be bad and letting power backfeed or is the speaker probably bad?
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You need to go back into that sound output section, and study it closely. Look at all of the operating voltages at critical points. Sound output tubes very often doubled as series-pass voltage regulators in some of those old sets. The sound output tube provided sound to the speaker--and B+ off its cathode to tuner and IF stages--both pix and sound. All of those voltage settings as shown in a schematic are critical not only for sound but for other functions in the set that you've perhaps not as of yet addressed. You need to do so.
The other area concerning sound is in the sound detector stage. This is usually either a ratio detector or a quadrature detector. Such transformer or coil could probably need minor ferrite slug adjustment to get the sound clear again. But this is on the basis that you've already covered all of the capacitors in the set. That must be done before you take the neut-stick to any transformer or coil slug.
12-27-2009, 10:18 PM
Linear Mode
