Are these things I should consider bad

[TinCanAlley]

Originally Posted by zeno

Is that the main B+ or one of the video outputs ???
The video out B+ is 240 VDC & filtered by C270. This cap
is notorious for causing jailbars in almost any brand.
Check C270 before going further.
In any case there is 5V of garbage there that shouldnt be.........

73 Zeno

Here's the B+ 240V that feeds the video outputs. Again, I don't know why I sometimes get two traces. I don't have a reference waveform to compare it to, but it does seem that there is ringing in it.

[old_tv_nut]

Originally Posted by TinCanAlley

Here's the B+ 240V that feeds the video outputs. Again, I don't know why I sometimes get two traces. I don't have a reference waveform to compare it to, but it does seem that there is ringing in it.

There is no way to tell if this is significant if you don't tell us the volts/division setting of your scope so we know what the peak-to-peak value of this waveform is.

Edit: I see you did tell the settings on a previous waveform. I suggest you check the filter cap as suggested by Zeno.

[TinCanAlley]

Originally Posted by old_tv_nut

There is no way to tell if this is significant if you don't tell us the volts/division setting of your scope so we know what the peak-to-peak value of this waveform is.

Edit: I see you did tell the settings on a previous waveform. I suggest you check the filter cap as suggested by Zeno.

It had the 10x probe on volts/div of 5 and time/div of 20.

I'll double check the cap. I is new and tested good w/in spec when I tested it before install.

[N2IXK]

What is the amplitude of that ringing on the 240V line? What is the DC voltage?

Can you try temporarily bridging another cap between 240V line and ground to see if it improves the bars or cuts the amplitude of that ringing?

Post the section of the schematic that shows C270 and this supply for those of without a Sams handy...

[TinCanAlley]

Originally Posted by N2IXK

What is the amplitude of that ringing on the 240V line? What is the DC voltage?

Can you try temporarily bridging another cap between 240V line and ground to see if it improves the bars or cuts the amplitude of that ringing?

Post the section of the schematic that shows C270 and this supply for those of without a Sams handy...

You'll have to forgive my lack of knowledge. I'm learning how to use the scope as I go along. All I can tell you is it was 5 volts/div with 10x probe and 20us time/div. How can I get the amplitude of the ringing? Do I increase decrease the volts/div and use the vertical scale just on the ringing portion?

As for the cap, I know I need one over 240V, but is there a particular value I should use? Also, should I parallel it with the current one or can I just find a 240V source and put the cap on it to ground?

I've attached the section of the schematics with the C270 a 10uf 300V. The T207 is the Flyback.

[N2IXK]

The waveform looks to be about 1.5 divisions peak to peak, so that could be either 7.5V or 75V, depending on whether or not the "5V/div" is taking the 10:1 probe into consideration.

75 vpp ripple on a 240V supply is a problem. 7.5V, not so much.

The doubled waveforms might be caused by improper triggering. Make sure you are triggering on whatever channel the probe is connected to, and if your scope has a TVH trigger mode, use it. Try rocking the trigger level back and forth around zero, and see if that makes the trace clearer.

I would start with the same value cap as you already have installed, and putting it right in parallel should be fine if it actually goes to ground. The attachment isn't showing up for me...

[TinCanAlley]

Originally Posted by N2IXK

The waveform looks to be about 1.5 divisions peak to peak, so that could be either 7.5V or 75V, depending on whether or not the "5V/div" is taking the 10:1 probe into consideration.

75 vpp ripple on a 240V supply is a problem. 7.5V, not so much.

The doubled waveforms might be caused by improper triggering. Make sure you are triggering on whatever channel the probe is connected to, and if your scope has a TVH trigger mode, use it. Try rocking the trigger level back and forth around zero, and see if that makes the trace clearer.

I would start with the same value cap as you already have installed, and putting it right in parallel should be fine if it actually goes to ground. The attachment isn't showing up for me...

The probe was in the 10x mode. Also, the triggering is from a Leader LCG-396 Pattern Generator.

The cap is connected the following way. There's a lead from the flyback to a leg of a diode, the other leg of the diode connects to a leg of a 150 ohm 2W, the other leg of the resistor goes to the positive side of the cap and a lead that connects the 240V around the chassis and finally the cap goes to ground.

I'll have to find a local source for a 10uf 300V cap. The local Radio Shack doesn't have them in-store. Must be a place around here somewhere. Not looking forward to paying 7 bucks for shipping of a single cap.

[N2IXK]

Originally Posted by TinCanAlley

The probe was in the 10x mode.

But some scopes can automatically detect the probe setting, and adjust the vertical scale range to reflect the probe attenuation and prevent confusion. This requires both a scope and a probe that support this feature. Do yours?

If your scope is doing this, then the scale really is 5 volts/division. If your scope or your probe doesn't do this for you, then the scale is actually 50 volts/division. This makes all the difference in the world when trying to interpret the waveforms as ripple on a power supply rail.

[TinCanAlley]

Originally Posted by N2IXK

But some scopes can automatically detect the probe setting, and adjust the vertical scale range to reflect the probe attenuation and prevent confusion. This requires both a scope and a probe that support this feature. Do yours?

If your scope is doing this, then the scale really is 5 volts/division. If your scope or your probe doesn't do this for you, then the scale is actually 50 volts/division. This makes all the difference in the world when trying to interpret the waveforms as ripple on a power supply rail.

I have a Tektronix 465M. No auto settings for the probe.

I've been thinking about the waveform. It's a 240V source, so the 5V/Div would be too low to show it and the 10x probe would make it 50V/Div and it would cover almost 5 divisions. What I got was way under that. I'm going to use the DMM to go all the way back to the boost diode and when I find the point it's 240V, I'm going to scope it. With a setting of 5V/Div and the probe in 10x, I should get a form that covers over 4 divisions, right?