Originally Posted by Username1 (Post 3081740)

Sorry I have very few Sams. Not to throw more confusion into this, but this is a video that goes over the concept of O'scope bandwidth, and is good for your problem.

http://www.youtube.com/watch?v=oZ1Dv2dVGkU

After the 2:50 point he starts getting into the "ringing" on an otherwise low frequency oscillator, and the bandwidth you will need to find your problem.

This video shows a little about roll off and why your scope should have a bandwidth well above what you actually want to be able to measure. And it all comes down to what makes up a wave form. He does not go into it here, but a square wave of 1khz actually needs a bandwidth multiple times that 1khz to be accurately displayed on an oscilloscope.

http://www.youtube.com/watch?v=pGwL6FadC9U

Your oscillation is about 10X horiz scan rate, easy to see as you have at least 10 visible vertical bars on the screen, As stated, around 200K, so you will need a scope that has a 1mhz bandwidth to see the ringing clearly. The above video explains the roll off of the scope, and why partly the bandwidth should be 1mhz. He is correct in this.

Another person asks if the bars get darker if the contrast knob is turned. With the same white screen, no signal, when turning the contrast knob through its range, does the bars change in their appearance? If not the noise is getting in other than the video amplifier circuit, (power supply because of bad decoupling cap) if they change significantly then the noise is being amplified by the video amplifier. So its a signal level noise.

Regardless of how the noise gets in, its source is likely at some point in the horizontal section. It is possible it can come from your corona source, does it intensify as you do something to cause the field to come close to arcing?

Other than that, there are two attached pictures from a tv I own, its not yours, but it shows parts near the horiz. area that can be culprits of your problem. Suspect any parts near the red dots, resistors, caps, inductors. You should go to the Sams website and buy your tv schematic, look around in the same parts of the tv, Horiz Osc, Driver, and output stages. There are two red arrows on one of the pictures, they point to waveforms that are capable of generating the "ring" because they are a pulse, and are squared. If a part that is designed to filter out overshoot in the pulse rise is bad, then the circuit, or following stage will momentarily oscillate at a higher frequency and give you that ring, and go into another part of the tv and give you those vertical bars...... Do not overlook shielding, of any parts, picture tube, or grounds.

This is a likely description of what could be causing those bars, its your job to look for a bad part in those areas, you will likely need the Sams, and possibly a good scope, and (2) 1mhz - 5mhz 10X to 1X probe with capacitance trimmer built in. There are good, inexpensive 20mhz - 100mhz Tektronix scopes and cheap starter grade probes that can be had for around $100. + Shipping, sometimes less. (Yes go for more than a 1mhz scope) You may need a second probe to connect to a horiz sweep sync source, as stated be another, so you better get two.

Originally Posted by Username1 (Post 3081748)

Even with a good scope, you may or may not be able to see the ring in the wave form. First Sams will have to had put it in the schematic, Its always possible they just don't chose to show a spot that happens to be the source of this specific problem, and second, you/he would have to be able to pick up on it, and then be able to figure out where its coming from. If it's not confined to one spot, its possible it shows up all over the set, then its back to checking individual parts. And who knows, it could be coming from the flyback, and just transmitting that into some near by improperly shielded item. Anyway, it looks like its a big enough disturbance that it can be tracked down.

Originally Posted by Username1 (Post 3081740)

Other than that, there are two attached pictures from a tv I own, its not yours, but it shows parts near the horiz. area that can be culprits of your problem. Suspect any parts near the red dots, resistors, caps, inductors. You should go to the Sams website and buy your tv schematic, look around in the same parts of the tv, Horiz Osc, Driver, and output stages. There are two red arrows on one of the pictures, they point to waveforms that are capable of generating the "ring" because they are a pulse, and are squared. If a part that is designed to filter out overshoot in the pulse rise is bad, then the circuit, or following stage will momentarily oscillate at a higher frequency and give you that ring, and go into another part of the tv and give you those vertical bars...... Do not overlook shielding, of any parts, picture tube, or grounds.

Originally Posted by Username1 (Post 3081755)

If you replaced the Horiz osc board with a known good one, move on, If you have a known good voltage divider and want to replace it, do so, then move on. With parts of the Horiz. circuit out of the way, move on over to the flyback, and parts that may be mounted near it.

You will have to check items on the chassis that are part of the horiz. that are not on the module.

When you say diodes had their leads cut then resoldered, did they cut one side, then resolder, or cut both sides...? Both sides may mean they chose to replace the part from on top of the board, I have seen that before, cutting one side may just be to test it with a vom.

Originally Posted by TinCanAlley (Post 3081728)

If I turn down the brightness, the screen goes black no matter how high the contrast is set. Because of this, I can't see if the bars are still there. Now if I turn the contrast all the way down and the brightness all the way up, I can see faint bars.

Originally Posted by old_tv_nut (Post 3081757)

Ok - so basically the bars are stronger when contrast is turned up, which says that at least a good part of it is in the video signal.

Originally Posted by TinCanAlley (Post 3081726)

I have jumpers with alligator clips, would those be good for grounding? I can clip from ground to ground on the modules and then to a good chassis ground...

Originally Posted by old_tv_nut (Post 3081759)

Yes, these are exactly what you can do to experiment. Be cautious and make sure you don't connect to something besides ground. Turning the set off while setting up the connection is a good idea.

Regarding all the other questions about your scope, I see you are getting a good one to work with. When you have that, you will be able to use one channel/probe to sync the scope to horizontal and the other to look at various points for your problem.

If it is a ground problem, however, you may see the bars change when you hook up the probe ground leads to the chassis or circuit cards, the same as experimenting with clip leads. This could be either exasperating or fun, depending on how you want to think about it!

Originally Posted by TinCanAlley (Post 3081758)

I guess I should have asked this a long time ago, but which part of the jail bars is not supposed to be there? The light or the dark bars?

Originally Posted by TinCanAlley (Post 3081756)

They cut only one lead and resoldered. I'm assuming they were testing, found nothing and soldered the leg back. No replacements were done.

Okay, just purchased a Tektronix 465M Oscilloscope, NIST-certified, Guaranteed & NIST calibrated off ebay. Hopefully it will be here around this time next week. :banana:

So I guess I'll just change the divider and let her be until the scope arrives. Now you said I need two probes? If so, I'll order another of the one I already have.

Originally Posted by Username1 (Post 3081776)

A 465M is a really good scope, one of my favorites, Calibration certified means you can get your money back if you decide to sell one day. I bet it was expensive, be sure you get the papers. Be sure to get probes so you can use it when you get it.

2 probes are an option, your scope will get a trigger signal off whatever you apply to one channel, the second probe is just in case you need to use a separate trigger source, good idea to have for some needs. Be sure you get ones with 1x 10x options and trimmer adjustment for capacitance, this will match impedance properly. Your scope has a square wave test point on its front, attach the probe, and adjust the trimmer to get a nice square wave with no overshoot, or loading (rounding of the square edges).

Just for the heck of it, when you just set that tv up to run as normal, and wack it a few times does anything happen to either the sound or picture that would indicate any loose connections, since this is a module set, any indication of disturbance while hitting it may mean you have bad plugs, or connectors on the boards....?

Originally Posted by Findm-Keepm (Post 3081783)

One question that doesn't seem to be answered in the previous posts - what is your signal source? Is it a cheapo DVD player, or some sort of RF Modulator? I can get jailbars on any set, tube, solid state, B/W or Color with my cheapo Conar bar-dot generator, so it could be signal source, plain and simple.

Cheers,

Originally Posted by Username1 (Post 3081776)

2 probes are an option, your scope will get a trigger signal off whatever you apply to one channel, the second probe is just in case you need to use a separate trigger source, good idea to have for some needs. Be sure you get ones with 1x 10x options and trimmer adjustment for capacitance, this will match impedance properly. Your scope has a square wave test point on its front, attach the probe, and adjust the trimmer to get a nice square wave with no overshoot, or loading (rounding of the square edges).

Originally Posted by Eric H (Post 3081789)

If you still haven't changed the Focus Divider I would start with that.

If it's arcing then it's defective, anything defective in the HV circuits has the potential to put interference on the screen, so start with that then look elsewhere if that doesn't help.

Originally Posted by TinCanAlley (Post 3081791)

That is on my list for tomorrow. You wouldn't happen to know how the pink lead is connected in the anode cap, do you? It looks like it is just pushed into the cap through the hole next to the anode lead.

Originally Posted by TinCanAlley (Post 3081791)

That is on my list for tomorrow. You wouldn't happen to know how the pink lead is connected in the anode cap, do you? It looks like it is just pushed into the cap through the hole next to the anode lead.

Originally Posted by Eric H (Post 3081795)

Is there a screw in the center of the cap on the inside? If so you probably just loosen that screw and pull out the old wire, reverse process to install.

Originally Posted by TinCanAlley (Post 3081800)

I haven't removed the cap yet, but if I look closely, the pink lead from the divider isn't all the way forward like the anode. I'm attaching a pic. It's the best one I have of it clean. I can find plenty of pics when it was dirty and you couldn't see through it.

I guess I'll know tomorrow when I ground it and remove it.

Originally Posted by Eric H (Post 3081789)

If you still haven't changed the Focus Divider I would start with that.

If it's arcing then it's defective, anything defective in the HV circuits has the potential to put interference on the screen, so start with that then look elsewhere if that doesn't help.

Originally Posted by zeno (Post 3081819)

Thats the old style connector. If you have a NOS tripler use
the larger brown one off it. Usually they have a small phillips
clamping the wires down. Thats IF it has 2 holes !

The 103-193 came in at least 2 styles. Fat grey ones & later
plain old black. Dont worry about them unless they have been
changed.

Grounds I assume you checked the terminal strip grounds.

When u attack the jail bars. I think you have a generator.
Hook it up & if it has a staircase pattern ( stripes going from
white to black across the screen) look at the video with the
scope. You will see two lines of a staircase. This shows you
how the levels relate to the pattern. Go to the IF output
( point 38 or C1 on Sams)
first at 7875 cycles & you will see 2 lines of the pix complete
with staircases at apx 1.5 V. This is raw unblanked video
sync & all. Next put the generator on blank raster.
If the bars have been introduced at that point you will
see 10 little bumps, if not nothing but a line between the
horz pulses. Work your way to the right Q203 B, Q203 C,
Q204 B, Q204 E, etc until you see them. The pattern will
get bigger & be blanked but you will see two lines.

One other thing. Odds are this set ran for years with too
much HV. Check the ABL that is off the tripler at R362.
CR223, R359, 360, Q201 etc.

While you are at it get an old book or look on internet for
what the things on the scope are. Sync pulses,
burst, back porch, blacker than black etc. It will help you
a lot.

73 fer now Zeno:smoke:

Originally Posted by TinCanAlley (Post 3081835)

Would this generator work for what I need to do? It seems to also have a horizontal output, so I think that might help with the scoping?

http://www.ebay.com/itm/LEADER-ELECT...item1c35b17803