I'm not a TV guy, but I thought I'd dabble. I picked a set that has a good raster.  It has a 10 inch CRT.  Slightly unstable picture (horizontal) when it's hooked to my source (DVD player, HDMI to RF converter and a balun), but my first interest is the sound. It's buried under a loud hum, so I suspect the filter capacitors. They are 100uf at 450v, so I have them on order.

I obtained a SAM'S Photofact. My first task is to get it apart, out of the case.

 4 stubborn control knobs and 16 screws later, I was able to pull it backwards out of the case. I hope I haven't bit off more than I can handle. I've tested a few of the tubes that I have access to, but I'll need to unmount these PC boards to get behind them. I retested to make sure I hadn't damaged anything in the process. What I did notice was the audio OK when first turned on, but the hum getting stronger as it warms up. To me that indicates a tube or resistor problem.

I do notice some newer parts, so someone has been in here before. So far, one of the audio tubes tests weak and glows oddly in my tester. A replacement has been ordered. The replacement was as weak as the first one, a 12CU5. I've had 3 of these now and they all test a little weak, so I assume that's just how they are. The audio is a little better. Without my source connected, the hum disappears. The hum increased with volume, so probably not e-caps.

Tested the rest of the tubes.The 5J6 mixer/oscillator tube is bad. Another on order. This may actually have something to do with the horizontal tearing, but I doubt it. Fingers crossed.

The new 5J6 made it worse, the picture has now gone negative. On researching, I suspect my source is providing too strong a signal and overwhelming the AGC. There doesn't seem to be a control to adjust, so I'm going to try putting an attenuator in the line.

The attenuator got my picture looking good, but added  hum to the audio. I'm using a 6db attenuator now. I'm getting suggestions from AI. I'll try to do and audio alignment. But first I've ordered a 3db attenuator and I'll see if that's the sweet spot.

20db seems to work well with the video., but increases the buzz which AI says is a result of the decreased audio signal with a bleed over from the video signal. I've relpaced 2 more tubes and a couple of resistors which helped a little. What helped most was doing an audio alignment, tweaking 3 coils. This brought the audio in clearly, with just a little buzz which I think I can dampen further by small adjustments in the fine tuning and the audio coils. I also found an adjustable attenuator (vintage) made by Radio Shack. I can dial it in better, getting my video and minimizing the audio buzz. It's not marked, but I think I'm probably around 16-18db attenuation.

 Finished 9/29/2026