More screen anomalies

[TinCanAlley]

Originally Posted by Username1

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.

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.

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.

[old_tv_nut]

Originally Posted by TinCanAlley

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.

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.

[TinCanAlley]

Originally Posted by old_tv_nut

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.

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?

[old_tv_nut]

Originally Posted by TinCanAlley

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...

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!

[TinCanAlley]

Originally Posted by old_tv_nut

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!

About now I'm wishing I had a test jig. This poor set has been on it's side and top so I can get to the underside for testing and repair.

[old_tv_nut]

Originally Posted by TinCanAlley

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?

Neither. The jail bars are a plus and minus (darker and lighter) (sinusoid) added to the nominal signal. Ideally you would see only the average brightness all across a blank picture.

[Username1]

Originally Posted by TinCanAlley

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.

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.

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....?

[TinCanAlley]

Originally Posted by Username1

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....?

I have one 10x probe already (just purchased it a couple of weeks ago) and have order a second one. They do have the trimmer adjustment, so I think all will be good when the scope arrives.

The scope is supposed to come with a calibration certificate. I'll probably keep it afterwards and start scoping anything and everything. I know if I get rid of it, I'll need it.

I guess I can use something to tap around on the chassis and modules to see if there's something loose (think I have a drum stick around somewhere). Whacking the set does no good as it's a solid cabinet and only serves to sting my hand.

[Findm-Keepm]

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,

[TinCanAlley]

Originally Posted by Findm-Keepm

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,

The jail bars are there with two different RF modulators, two VCRs and one '87 laserdisc player with built-in RF. Now unless the bars could be caused by the AC line, I think it's the set.

Is there something else I can try? I wish there were a broadcast signal I could tune into. I do have a Blonder Tongue Agile Processor. Maybe I can get it to broadcast a signal on a VHF channel and use the good ole rabbit ears.

[TinCanAlley]

Originally Posted by Username1

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).

I do have a question about test points. In the Sams it shows a test point between one leg of the vertical transistor and one leg of the horizontal blanking transistor. Seems the two legs are tied together and then a resistor goes to ground from that solder point. Now the test point is right at that junction and it can only be reached from the bottom of the chassis. Is it important to get that point or can I just connect the probe on the top side directly to the leg of the blanker transistor? Either way it's on the same end of the resistor, so that's not an issue. It's just not at the solder point of the two legs.

I hope that makes sense.

[Eric H]

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.

[TinCanAlley]

Originally Posted by Eric H

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.

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.

[Eric H]

Originally Posted by TinCanAlley

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.

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.

[jr_tech]

Originally Posted by TinCanAlley

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.

I have never messed with anything that new, but in all that I have seen the clip is soldered to the HV lead. Grease up the lead where it enters the cup and push it further into the cup, while gently pulling the clip out of the cup. The clip should come out of the cup so that you can unsolder the wire and pull it out. Push the new wire in and solder to the clip, then pull it back so that the clip is seated in the cup as before.

jr