Zenith jumpy picture ...

[rwagoner]

Originally Posted by damen

look closely at the 9-959 main board and see if there are any "blue" color caps. They would leak. You could see corrosion on the leads as they enter the board. Also, does this set have the extra PIP module ?

It does not, unless it is there and disabled. I never had PIP as an option in the menus.

Think it might be worth just changing all the caps on the 9-959, especially if they are blue?

[damen]

Changing them would be a good place to start. I've had issues with them causing sync, color, and video problems.

[rwagoner]

I will do that ... as soon as I get a little more time, and report back asap.

THANKS!

[rwagoner]

Today I tool out the main board to look for leaking or bulging capacitors. I did not see anything bad. I obviously can't see under the caps that are mounted right on the board with no space, but didn't see anything suspicious at all. I also looked at the sweep board and everything looked pretty clean there as well.

So I put it all back together and tested it to make sure it was at least at the state it was before. It was ... kind of reminded me of a scrambled picture from the old ON-TV or SelecTV days. I left it on for a while to see if it would still clear up a little, and it did. Seemed to get better faster, but honestly I could not really tell for sure. After a while I was able to watch a fairly stable picture.

Here's where it gets weird. I am not sure if it's related to my leaving the VCR/DVD player "on," but I turned off the TV for a few hours. When I turned it on, the picture was almost watchable right from the start. I could watch the DVD I had in the player with just a little jumping, and the FireTV stick going through the converter to the RCA inputs -- though jumpier at first, settled soon after being on. This pattern repeated a few times during the day.

Just now I turned it on, and the picture was almost stable right from the start even on the Fire stick. Right now it is playing Adam 12 via the Fire stick flawlessly, just a few minutes after turning it on.

This is a total longshot, but is it at all possible that leaving the combo VCR/DVD player "on" sent enough of a signal through the RF antenna input that it "heated" the bad part and made it stay more stable?

And more importantly, would that in any way give clues as to what part of the board may have a bad part? Capacitor or not?

Alternatively, are there any recommendations for a repair place near the South Bay area of Los Angeles County (San Pedro, Rancho Palos Verdes, Torrance, Lomita, etc) who might be able to do a true diagnosis?

[old_tv_nut]

The RF output of a player is far, far too small to cause any heating.

[rwagoner]

Am planning to look into this again in the next few days. Was wondering - I originally thought it was a vertical sync problem; as it got worse (the temporary almost working condition didn't hold!) it seems more horizontal in nature. I may have already said it, but at times the picture looks quite like the old scrambled signals you saw with ON-TV and SelecTV over the air subscription TV. The on-screen menus NORMALLY look fine even with the picture "jumping," but if the picture is REALLY bad the menus go with the picture. The menus always look fine when you turn off the video source or switch to an unused or unconnected input.


More likely it is both vertical and horizontal though.

From an old post, there was mention of a capacitor in the flyback circuit ... is that a possibility, or if the menus normally/usually look OK does that rule that out?

I am still wondering if I should concentrate on the sweep board or the main board. Sweep includes the power supply.

I was thinking of just replacing a few capacitors at a time and seeing if that eventually catches the problem ... but again - on the main or the sweep board?

Thanks as always

[zeno]

Its safest to get a manual & just change related caps. Problem is probably on the signal board. Most likely in AGC OR sync. The little cube style 9" sets
of this era used to get a similar problem, a little electrolytic.

Zeno

[liammc00]

Originally Posted by zeno

Its safest to get a manual & just change related caps. Problem is probably on the signal board. Most likely in AGC OR sync. The little cube style 9" sets
of this era used to get a similar problem, a little electrolytic.

Zeno

I got one of those 9" sets and Luckily mine still works fine for now.

[rwagoner]

Well, this is odd. I finally had some time to do some work on it today ... it's been left unplugged for a few weeks (since my last post, probably). It's not jumpy right now ... working perfectly. Have not had it on long yet. Do capacitors ever work better after not being energized for a while? Doesn't seem likely, but I just don't get it.

[zeno]

This may be a good candidate for freeze mist. Start with the signal PCB
around the jungle IC. Spray small areas & if you get a reaction put
some freeze on a Q-tip & touch individual parts. I would almost guarantee its
one of those little electrolytics.

Be a shame to junk it. Its got a strong jug & one of Zeniths last good sets.
You can put pixs on it & maybe a bouquet. You cant do that with a LED set !

Zeno

[JohnCT]

Originally Posted by rwagoner

Do capacitors ever work better after not being energized for a while? Doesn't seem likely, but I just don't get it.

Generally speaking, no - it is usually the opposite - electrolytic caps love heat and hate cold.

When I suspect lazy electros, I get out my heatgun and warm up a section of the board and look for improvement. If the situation improves, it's likely to be a lazy cap.

Turn your boards over and look for dark spots from electrolyte leaking. It will look like a splotchy area.

Zenith caps of that area leak like crazy, but virtually never make themselves known by venting the top out in a nice bulge. But they do leak down their legs and it works its way to the bottom of the board. As it gets work, it attacks the solder mask and the solder connections turn dark gray or black.

If you see evidence of this, replace any cap on the top side that is over the splotchy bottom area.

John

[rwagoner]

Originally Posted by JohnCT

Generally speaking, no - it is usually the opposite - electrolytic caps love heat and hate cold.

When I suspect lazy electros, I get out my heatgun and warm up a section of the board and look for improvement. If the situation improves, it's likely to be a lazy cap.

Turn your boards over and look for dark spots from electrolyte leaking. It will look like a splotchy area.

Zenith caps of that area leak like crazy, but virtually never make themselves known by venting the top out in a nice bulge. But they do leak down their legs and it works its way to the bottom of the board. As it gets work, it attacks the solder mask and the solder connections turn dark gray or black.

If you see evidence of this, replace any cap on the top side that is over the splotchy bottom area.

John

I'll check again ... when I looked before I could not see any such damage. I wonder if one of the controller IC chips is going bad?

[liammc00]

A capacitor can be bad without showing any signs of leaking or venting out the top. What you need is to test the esr with an esr tester and If any of capacitor read high esr that means there out of spec. I don't know about all esr tester but mine can measure caps in circuit as long as there are not in parallel with a nother cap.
Here is one I have it is kinda pricey but very well made. Mine was a little cheaper as I bought the kit version not the already built one https://anatekinstruments.com/produc...esr-meter-besr.