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Recapped My Predicta Tandem, I don't know what to do
#38

Your B+ is good enough to have a raster. Both the horizontal and vertical oscillators are running. I haven't been reading too close. Do you have a Sams Photofact? Or something with waveform drawings? It should have voltages too. Also you will need a scope. It doesn't need to be anything special.

I see from your pics that the horiz osc looks to be running too fast. and the vertical waveform driving the yoke is distorted and or way too fast that's why the foldover and saggy picture. Most likely caps causing the distortion. Look for tired resistors too. Oh and apparently the tube sockets are fragile. They break it where they clamp the tube pins just from pulling the tubes out.

Again once you know the voltage here is good. I would start on the vertical deflection it doesn't depend on the tuner, IF, or the horiz section. It's pretty straight forward. It runs at only 30hz. It should deflect full screen all by itself.  Again double check the caps found there and make sure It is wired correctly. Look at the waveforms here and look to the vertical output tube for goodness. The sams will have test points to check with an oscilloscope. You will also need a tube tester or a known good output tube. It takes some watts to drive the yoke.

Adjusting the vert and horiz controls just speeds up or slows down the oscillators so they will lock to the incoming signal IF.  Look to see if the pots are dirty or dead.

Set the vert adjustment at half way and find the vertical oscillator coil and try to lock the picture in. Don't be afraid here.  The oscillators only need to be close enough to lock in. I would use a large mirror so you can see while you are behind the set twisting on things.  You should be able to see the rolling speeding up on not. If you can get the picture to stand sill but won't lock the sync-intergrader in not working. That's the next chapter. 

  Watch a bunch of tv repair videos and it will start to stick in your brain. There a ton of videos.

!!!!!!!!!!!!!!!!!!!RESISTANCE IS FUTILE!!!!!!!!!!!!!!!!!!!!!!  
                           /\/\/\/\/\/\/\/\/\
                                                     
                                 [Image: http://philcoradio.com/phorum/images/smi...on_eek.gif]  Chris


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RE: Recapped My Predicta Tandem, I don't know what to do - by OZ4 - 01-08-2022, 10:14 PM



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