I finally got one!!! Philco Predicta

[static1701]

I replaced the replacement caps in the vertical section and I have deflection!!!
It rolls a bit but it is working. Super happy to have gotten this far.

[static1701]

Need some help, I have replaced all the caps and resistors in the video and horizontal sections but I can’t get a stable horizontal lock. It wants to pull to the right. Adjusting the contrast affects it as well.

[Electronic M]

The horizontal AFC diode pack may be bad.

[static1701]

Originally Posted by Electronic M

The horizontal AFC diode pack may be bad.

What values are they? I am guessing I will have to make something.

Thanks,

Scott

[Electronic M]

The schematic should at a minimum give you a part number you can search a data sheet for.
Usually the original was a 2 diodes Ina 3 leg package.
You want a replacement with the same or greater Piv and forward current ratings and a fairly fast switching time. Most will favor shotkey diodes for their fast switching time and the broader horizontal locking range they give, but you can often get away with 1n4007s especially if you need a quick temporary sub to confirm the original is bad.

[static1701]

Originally Posted by Electronic M

The schematic should at a minimum give you a part number you can search a data sheet for.
Usually the original was a 2 diodes Ina 3 leg package.
You want a replacement with the same or greater Piv and forward current ratings and a fairly fast switching time. Most will favor shotkey diodes for their fast switching time and the broader horizontal locking range they give, but you can often get away with 1n4007s especially if you need a quick temporary sub to confirm the original is bad.

Thank you!!!!!!!!!!!!!!!

I replaced the 34-8037 (D1) with a couple of Shotkey diodes I had left over from another project and I can get a reasonable stable lock now. It wiggles a little bit but over all it is stable. I am guessing the diodes I have are not the right ones.

Video: https://youtu.be/zOQZrGYF7d0

[old_coot88]

You do have them connected common-cathode (banded end to banded end), right?

[static1701]

Originally Posted by old_coot88

You do have them connected common-cathode (banded end to banded end), right?

Yes, just attached to test clips for now.

[old_coot88]

Is the old dual diode out of circuit?

[static1701]

Originally Posted by old_coot88

Is the old dual diode out of circuit?

Yes, I changed to some different fast diodes and the picture was rock solid. But I don't think they can handle to power, the set has reverted to rolling a bit and the picture is not centered. I will need to get the correct replacement.

The picture is from when I just tried the fast diodes.

[static1701]

Figured it out:

One of the legs of the N5 broke loose. Re-soldered it and everything is fine.

[kvflyer]

Originally Posted by static1701

Figured it out:

One of the legs of the N5 broke loose. Re-soldered it and everything is fine.

[static1701]

I finished replacing all the resistors on the main
Board. I have a buzzing in the sound when txt is on the screen. Going to work on the IF board next.

[static1701]

I replaced the resistors on the IF board, the set works very well. I am happy with it, so I am not going to mess with anything else. I still need to buff out the scratches in the safety glass and get the rust off the stand. Over all, it was by far the hardest set I have repaired. Thank you to everyone that helped me get it working.

[static1701]

I was going to let it be, but I brought it in the house and the buzz that it does when text is on the screen is a pain. It is minimal but I would like to resolve it. What causes that?