Sony TV-700U getting audio but no video

[matthewray2b]

Originally Posted by jr_tech

On the best channel, does the picture change when you adjust the fine tuning control? If not, the control is possibly not engaging.

jr

If by "fine tuning" you mean the Horizontal Frequency knob then yes, it is engaging. You can see it working in the video.

[jr_tech]

No, I mean the fine tuning knob...the outer ring around the channel selector knob. Push to engage.

jr

[matthewray2b]

There's a knob on the left that goes from 14-83.... Is that what you mean? When I turn it it doesn't seem to do much.
However, it looks like when I bump the main channel selector it changes the screen quite a bit. I think I'm gonna clean that knob and see what happens.

[jr_tech]

No, that’s the UHF channel selector. Perhaps the fine tuning knob is missing?

jr

[matthewray2b]

Ah, the fine tuning knob was a second knob that went around the channel selector. Used it, made a big difference. I was still getting a handful of vertical lines that were dimmer than the rest of the screen and couldn't get the screen to not be tilted right but I'm guessing that can go away with just more fiddling?

I can post another picture or video if it would help. Obviously it won't look amazing but it might help.

[jr_tech]

Yes, please post a current video.
jr

[old_tv_nut]

Ditto: please post another video.

But before you do, did you set the channel selector to channel 3 and then adjust the fine tuning? Most games, VCRs, etc. output to channel 3. They may have a switch to select channel 3 or 4, but most commonly they are used on channel 3.

[matthewray2b]

Here's the vid. Should be on channel three. I am now in the process of cleaning the channel selector pot.

https://www.youtube.com/watch?v=8aVixtKT1cQ

EDIT
I cleaned the channel selector and fine tuning pots and it seems to be much smoother but still am not getting it just right yet.

[matthewray2b]

I guess my next question would be how do I know if the fine tuning is adjusted correctly without the hfreq being in the correct position?

[old_tv_nut]

Originally Posted by matthewray2b

Here's the vid. Should be on channel three. I am now in the process of cleaning the channel selector pot.

https://www.youtube.com/watch?v=8aVixtKT1cQ

EDIT
I cleaned the channel selector and fine tuning pots and it seems to be much smoother but still am not getting it just right yet.

At this point you are wasting de-oxit. If there is something left needing cleaning, it's internal, not reachable from the knobs outside,

It's hard to see in your video because it's overexposed, but it appears you did not find any good fine tuning spot. When the tuning is correct, the diagonal stripes should change to dark diagonal bars (sync and blanking pulses) about 1/10 the width of the screen, and the horizontal and vertical should then lock in solidly.

The picture you are getting is like a bas-relief of the normal signal, showing only the edges of the sync pulses and not nice solid black pulses, and the sync circuits can't lock to that. This normally happens when the fine tuning is way off or the TV and game system are not set to the same channel, but there could be some other cause, I guess.

Can you post a video of how your game system is connected to the TV, in case there is a problem there? Show: where the cable is connected to the game and where the cable is connected to the TV, and any adapter between the cable and the TV.

[old_tv_nut]

Here are some images, all with good fine tuning, for reference. I was not able to find an image of bad fine tuning, but it is essentially what you are seeing. All three pics show a standard "Indian Head" test pattern.

Normal picture with test pattern


Picture with normal fine tuning, but sync is floating. (You have floating sync, but it's probably due to the poor tuning, not due to a sync circuit failure.) Note the dark horizontal and vertical sync bars.


Picture with normal fine tuning but horizontal hold (H) control or horizontal frequency control is misadjusted

[matthewray2b]

Okay here's the third update. This ones a bit longer cuz I went through and did all your requests. There is a bit of talking too. Feel free to put it at 2x speed.

https://www.youtube.com/watch?v=bqKhFlhO_lo

[old_tv_nut]

Originally Posted by matthewray2b

Okay here's the third update. This ones a bit longer cuz I went through and did all your requests. There is a bit of talking too. Feel free to put it at 2x speed.

https://www.youtube.com/watch?v=bqKhFlhO_lo

At about 5:00 minutes, the "tangent lines" you point to are the edges of what should be the solid dark bars. Although this is the best fine tuning you have obtained ar this point, it still looks like you are far off the proper tuning point. This effect of seeing edges only means that you are getting only the higher video frequencies (which make edges) and not the whole signal (which would inlcude lower frequencies as well that make solid areas).

The blurry vertical black bars you see earlier in the video are from being very far mistuned, such that you are picking up almost none of the signal and instead are seeing effects of the TV interfering with itself somewhat. (The very high currents in the horizontal sweep can produce a weak interference signal that is invisible compared to a good, properly tuned-in signal from your game.)

"Bas relief" is pronounced "bah relief" and means a shallow carving in stone.
https://www.britannica.com/art/bas-relief

Your sync is not totally floating - the image jumping around or tearing the way it is indicates that the sync circuits are trying to work but are not getting a solid signal to work with.

Turning the H frequency and H hold should find a condition where the diagonals go more or less straight up and down (but still jumping around) and then go diagonal the other way as you adjust further. You had this condition in the earlier videos.

At 8:49 you turn the horizontal frequency and you do get this condition. This is an indication that the H adjustments are good, but again, the sync circuits can't work properly without a solid signal.

Around 9:00- 9:30 you can see a hint of the solid dark sync bar on the left but the main effect is the white "bas relief" edges.

There is still a possibility that the tuner or IF (intermediate frequency) amplifier section is bad in some way worse than just fine tuning. It would be hard to diagnose without opening the set and having the right test gear.

I don't know what the mechanical details of the fine tuning are on this set. I would expect a range of multiple turns with a stop at each end, but the stop could easily be broken. In that case it is possible that the tuning element would fall out of its place fi you tuned too far, but that hasn't happened because you are still getting a tuning action.

Have you been able to go beyond the current best fine tuning point and see if it continues to get better or gets worse again?