I see the ringing, but what's the other stuff

[TinCanAlley]

Okay, started scoping again. The last time I got the ABL scoped and saw the ringing. Today I decided to make sure the pulses from the horizontal board are correct before going on to other areas. They all check out.

Since the ringing was found at the ABL, I figured the best route was to go backwards from there. I just scoped the vertical blanker's base and got the attached image. That's a crap load of ringing! Not only that, but what are the stray lines in the waveform? I did my best to capture them as they're moving around quite a bit. I don't know if it's bad or part of the form.

Anyway, I'll be moving my way up the chain. Wish me luck.

[TinCanAlley]

Another question....

Should I see this horizontal waveform on the base of the vertical blanker? Or, is it disregarded by the circuit? If so, then I'll ignore it.

[TinCanAlley]

Okay, the attached is where the ABL's base gets its signal. So if it's on the base it has to be coming from here somewhere.

There's a 15ohm pot (brightness limiter), 10ohm resistor on pot T2 to ground, 270ohm between pot wiper and base of ABL, spark gap, voltage regulator (7.5V Zener feeding T1) and a 500ohm resistor.

Am I on the right track? I don't see how the ringing can hit the base of ABL and not be from this area somewhere.

[lnx64]

You need one giant megathread, lol

[TinCanAlley]

Originally Posted by lnx64

You need one giant megathread, lol

Things in one large thread get lost/overlooked. I hate creating new threads, but it seems to help keep sub-issues and questions separate w/less confusion.

[lnx64]

True. :P

[TinCanAlley]

Anyone have any suggestions on this? I've been stuck since yesterday morning. I guess I'll just go ahead and replace all the pieces in the ABL circuit and see if that help.

[lnx64]

If you slow down the scopes sweeping speed and lower the sensitivity to make the traces a little smaller, what does it look like then?

[jr_tech]

It would be helpful if you would post the 'scope settings (volts per division & sweep speed) as well as the picture... Hard to tell if the ringing here is significant... perhaps it is a millivolt, perhaps it is 10 volts, we can't tell. I suspect that you are using a very sensitive vertical setting, and those random traces flying by are perhaps from pulses (vertical?) that are much larger, and off screen.
jr

[TinCanAlley]

Originally Posted by jr_tech

It would be helpful if you would post the 'scope settings (volts per division & sweep speed) as well as the picture... Hard to tell if the ringing here is significant... perhaps it is a millivolt, perhaps it is 10 volts, we can't tell. I suspect that you are using a very sensitive vertical setting, and those random traces flying by are perhaps from pulses (vertical?) that are much larger, and off screen.
jr

I can't remember the exact setting, but it was with the 10X setting on the probe. I realize I was looking at the vertical blanker with settings for the horizontal. You're probably right about the voltage of the ringing being very low. My main attention now is the ABL circuit as the ringing shows up with .2 VPD and covers 4 divisions (which is about right since SM says it should be .8V and 15750 sweep). The ringing is clear as day on it. Roughly the same number as the jail bars on my screen.

[old_tv_nut]

You scoped the vertical blanker's base, which I assume is the input. What's important is what gets through to the output. It's very likely that the ringing on the base is clipped flat at the output and is not causing your problem, but you have to scope the blanker output to find out.

I also agree that it looks like you are sweeping too fast (horizontal rate) and with too much gain to see the whole waveform peak to peak at vertical rate.

[TinCanAlley]

Originally Posted by lnx64

If you slow down the scopes sweeping speed and lower the sensitivity to make the traces a little smaller, what does it look like then?

I've realized I was scoping the vertical with the horizontal settings. I'll rescope it with the proper settings and get back to you.

[TinCanAlley]

Originally Posted by old_tv_nut

You scoped the vertical blanker's base, which I assume is the input. What's important is what gets through to the output. It's very likely that the ringing on the base is clipped flat at the output and is not causing your problem, but you have to scope the blanker output to find out.

I also agree that it looks like you are sweeping too fast (horizontal rate) and with too much gain to see the whole waveform peak to peak at vertical rate.

You're all right. I did and I'm going to redo it shortly.

So the ringing I posted in another thread on the ABL was done on the base as the SM shows. The ringing is very noticeable there. It doesn't mention checking any other leg of it. Is that something I should do?