Capehart Farnsworth 661P Aquisition

[pendulum]

I removed the horizontal subchassis and ended up replacing a bunch of off resistors and it seems to have made a big difference! Vertical, horizontal hold and everything else is working great. As you can see in the picture however, there is some fold over at the bottom of the screen. I could get rid of it by adjusting the controls, but it reduced the size of the image too much for the mask. However, the one capacitor that I did not replace, 1ohm at 60 cycles 3v non-polarized, goes right across the vertical centering control. I did some math and using the capacitance reactance formula I figured this is about 2650uf. There also are a few resistors in the vertical linearity and height controls, so I will check those next. I also felt for how well the crt tested, I didn't have that great of brightness. However, there are also a resistor chain in the high voltage area which also may be off. Interestingly this revision of the chassis does not have a width control, so I will have to figure out what replaced it and check that area as well, as it stands the width is pretty close to correct for the crt size, but not perfect

[pendulum]

Well I must have made an error at some point. I was replacing the resistor chains in the high voltage area, along with the shorted ac cap and a few resistors on the pots. Now when I turn the set on and the flyback area kicks in something makes a horrible squeal. I was getting an image, and adjusting the horizontal sync control would change the noise, but I was not getting any image or sound like I did before. After turning the set on and off a few times I no longer get high voltage. I ohmed out the flyback and it doesn't appear that any of the sections are open, I'll have to check for shorts between the windings. My hope is that the problem is due to my replacing the resistors in the high voltage chain but not putting any insulating coating on them like was there before. I ordered up a can of corona dope and will see if that changes things when it arrives wednesday. The fact that adjusting the sync did effect the sound really makes me think there is some issue around the 6l6 and 1B3 tubes, though I don't know why this would also kill any sound or video.

[Phil Nelson]

Originally Posted by pendulum

My hope is that the problem is due to my replacing the resistors in the high voltage chain but not putting any insulating coating on them like was there before.

I didn't put any corona dope on those resistors when I replaced them in my 661-P, and it seemed to work normally. I did insulate their leads with shrink tubing and I took care to make all solder joints in that area very smooth.

If arcing is going on, you may be able to see it by turning on the set and observing that area in a completely dark room.

If anyone wants to look at the factory service manual, it's available here:

http://www.myvintagetv.com/Apple%20P...e%20Manual.pdf

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html