Pilot TV-37 Restoration

[Crist Rigott]

Fixed it. Ready for this. I adjusted the H. Hold and the severe bending at the top of the picture was gone.

However, the picture was still very dim. You see, I recapped my second TV-37 and that one had a lot brighter picture. Then I remembered that L17 has a 1N34 video diode that I never replaced. I pulled L17 and changed out the diode with a 1N34A, 2 resistors, and a 250pf mica cap. Reinstalled L17 and the picture was a lot brighter. I put my crosshatch generator on it and adjusted the vertical size, horizontal size and linearity, and picture centering. All is well.

Thanks to all for your suggestions.

Here are some pictures of the before and after L17.

[Kevin Kuehn]

That's very interesting. Those old germanium diodes seem to develop internal resistance over time and apparently yours was leaking some DC offset onto the video amp grid, messing with sync and brightness. Anyhow good fix.