Are these things I should consider bad

[TinCanAlley]

Originally Posted by jr_tech

I'm not sure that I understand your use of the term "lower" in this case... For example, if the scope knob is set for 10V/div and you use the 10x probe, is the waveform measurement on the scope now? :

a) 1V/div
b) 100V/div

jr

With the probe in the 10x mode it would be 10 volt / div. Isn't that how it works? If I set the scope to 1 volts/div and put the probe in 10x mode, it would reduce/lower/attenuate it by a factor of 10 and the display should be read as 10 volt/div?

[TinCanAlley]

Okay, just grounded the ABL's base leg and the jail bars remained. The only affect it had was to brighten the screen when grounded and go back to original brightness when ungrounded. So it seems the ABL circuit isn't to blame.

[jr_tech]

Originally Posted by TinCanAlley

If I set the scope to 1 volts/div and put the probe in 10x mode, it would reduce/lower/attenuate it by a factor of 10 and the display should be read as 10 volt/div?

That is correct, the "10x" is the *attenuation* factor, not a multiplier. It was not clear that you were reporting the actual voltages of the circuit or the amplitude seen on the scope, with or without taking into account the 10x *attenuation* of the probe, or worse still using the "10x" as a multiplier.
So "b" is the correct answer to my question... agree?

Now, where do you set the baseline "0 volts" before probing a DC voltage? If probing a positive voltage, I set the baseline to the lowest line on the 'scope face and count divisions up from there after the DC is applied to the probe. If unsure of polarity, I set the baseline (with no voltage applied) to the center graticule line and see which way the trace goes when probing the voltage.

jr

[TinCanAlley]

Originally Posted by jr_tech

That is correct, the "10x" is the *attenuation* factor, not a multiplier. It was not clear that you were reporting the actual voltages of the circuit or the amplitude seen on the scope, with or without taking into account the 10x *attenuation* of the probe, or worse still using the "10x" as a multiplier.
So "b" is the correct answer to my question... agree?

Now, where do you set the baseline "0 volts" before probing a DC voltage? If probing a positive voltage, I set the baseline to the lowest line on the 'scope face and count divisions up from there after the DC is applied to the probe. If unsure of polarity, I set the baseline (with no voltage applied) to the center graticule line and see which way the trace goes when probing the voltage.

jr

Yes, if the dial is set to 10 and the probe is on 10, then the display is 100 per division. I edited my original post to reflect the probe and dial setting.

For the DC I put set it to GND and moved the trace to the bottom of the screen and then switched to DC. It moved up as it was positive. Since the DC was showing a waveform, I moved the baseline to the top of the first division so it would show the entire waveform.

[jr_tech]

Originally Posted by TinCanAlley

Since the DC was showing a waveform, I moved the baseline to the top of the first division so it would show the entire waveform.

Ahhhh! that's where you lost me... the reported values did not *seem" to correlate to what I was seeing on the 'scope.
jr

[TinCanAlley]

Originally Posted by jr_tech

Ahhhh! that's where you lost me... the reported values did not *seem" to correlate to what I was seeing on the 'scope.
jr

My biggest issue is why the B+ waveform is so fat. I found that if I adjusted the trigger level I could thin it out, but then it would lose the trigger. To get it back I had to zero out the trigger level, but then I got the fat waveform.

I just scoped all of the B+ 125V to and from each of the modules. It was consistent throughout, if I thinned out the waveform, it was roughly 1 VPP before it lost the trigger. If you count the fat wavefrom, it would be roughly 3.5 VPP.

So I'm pretty sure 1 VPP of ringing isn't going to create the jail bars. That and I've pretty much ruled out the ABL.

Not sure where check next. I've done the horizontal oscillator, wave generator and output on the horizontal board. I don't have the probe necessary to do anything with the FB, yoke or HOT.

[TinCanAlley]

Okay, moved on the 240V boost section. I'm attaching three waveforms. Each are done at 50V/div and 20us/div.

The first is directly from the lead off the flyback where it connects to the boost diode. It's taller than my scope can display. I didn't realize it was 900V. Glad my scope didn't do something bad. I'm growing fond of it.

The second is on the other side of the boost diode and is now 248V. The waveform covers just over two divisions, so it's just over 100V and there's ringing in it.

The third is through a resistor and to the 10uf 300V capacitor. Again, I'm getting a really crappy waveform, but the basic form is the same as pic 2.

Now I tried scoping the other 240V boost, but I couldn't get a meaningful waveform. Where I scoped for pic two, it splits off from there to another point where it's connected to a 15ohm coil. It measures at 248V, but the waveform is pretty much non-existent. Don't know if it's the coil smoothing it out, or if my settings aren't working for it.

[jr_tech]

Originally Posted by TinCanAlley

Now I tried scoping the other 240V boost.

I don't understand "other"... are you saying that the set actually has *two* sources of 240 Volt "boost voltage"... I suspect that there is only one source and it is distributed to other boards that may be marked "B+ or 240V", but these are boards where the 240V is used, not produced?
jr

Add: same for the 125V supply... two sources would seem to be unlikely.

[zeno]

Yes C-1 is Zeniths term for composite video. Some sets
even have a "C-1 adjust" pot.
Grounding the ABL base proves its NOT coming from there so ignore
all between the ABL base & tripler.

Depending on the scope I was using I almost never used
DC only AC since I was looking at waveforms. On my sencore
there was a built in meter to speed things up.
Also be sure all your calibrations are set. The are the red
knobs are set to "cal". Some have an arrow to show which direction
to turn them.
If the scope is dual trace you can use sync on B to stablize the
waveform. Hook the B channel probe to a clean hoz signal
such as the hoz drive collector, this may get rid of the multiple
traces.

73 Zeno

[TinCanAlley]

Originally Posted by zeno

Yes C-1 is Zeniths term for composite video. Some sets
even have a "C-1 adjust" pot.
Grounding the ABL base proves its NOT coming from there so ignore
all between the ABL base & tripler.

Depending on the scope I was using I almost never used
DC only AC since I was looking at waveforms. On my sencore
there was a built in meter to speed things up.
Also be sure all your calibrations are set. The are the red
knobs are set to "cal". Some have an arrow to show which direction
to turn them.
If the scope is dual trace you can use sync on B to stablize the
waveform. Hook the B channel probe to a clean hoz signal
such as the hoz drive collector, this may get rid of the multiple
traces.

73 Zeno

I'm using the horizontal trigger of the pattern generator. Is that basically the same as using the B channel on a clean horizontal signal?

Yes, the red knobs are in the calibrated position. Not ready to mess with those kinds of adjustments.

When I check the C1, I get a staircase type pattern. Is that what it's supposed to look like? I have the pattern generator on the color bars w/IQW and chroma off. That gives me long b&w bars on the screen.

Inside the set there's a sheet glued to the wall. It has a section w/the heading of "Major Test Points". The first one is C1 (Picture Detector Output). The other two are used for calibrating the ACC and some IFAGC.