Ok. Let’s try this again…RCA 9TC240 Alignment

[Penthode]

Have you checked if the 6AL5 is lit?

[Chris K]

Originally Posted by Penthode

Have you checked if the 6AL5 is lit?

No not yet. I'll do that this evening

[Chris K]

6AL5 is fine. New scope in and working. Got the trace...BUT IT'S BACKWARDS!

[Penthode]

So the other scope was sick?

To ensure we are on the same page, please define backwards. Do you mean the x axis is scanning right to left? If so that suggests a polarity inversion on the x channel input.

And why is part of the trace darker? is the photo accurate to what you see or is there a shutter speed issue? If it a shutter issue, perhaps reducing slightly the scan trace speed will help.

[Chris K]

Originally Posted by Penthode

So the other scope was sick?

To ensure we are on the same page, please define backwards. Do you mean the x axis is scanning right to left? If so that suggests a polarity inversion on the x channel input.

And why is part of the trace darker? is the photo accurate to what you see or is there a shutter speed issue? If it a shutter issue, perhaps reducing slightly the scan trace speed will help.

Yes I believe the other scope was sick. This one gave me bright, clean and sharp traces.

By backwards I mean it's like a mirror image left to right like the trace rotated 180 degrees around the Y axis.

The picture being darker on one side is a shutter issue. It's a great trace, crisp, clear and of equal brightness intensity throughout.

[Chris K]

BUT...the markers are in the right places so maybe the rotation is with reaspect to the X axis

[old_tv_nut]

On a symmetrical trace like this, how do yoiu know if it's the horizontal or vertical that's reversed?

[Chris K]

Originally Posted by old_tv_nut

On a symmetrical trace like this, how do yoiu know if it's the horizontal or vertical that's reversed?

By the frequency of the markers. It's rotated 180 degrees around the X axis...my mistake earlier

[Penthode]

The 8601a is a ramp waveform sweep to the x axis input. If the trace is backwards, there must be a phase inversion switch on the x channel input at the scope.

[Penthode]

Is that an invert button beneath the volts/div control?

[Penthode]

And can you reduce the sweep speed slightly on the generator (little knob on the lower right from panel) so that the photos show a bright clear display for us?

And I should add that on late 40's RCA TVs, almost all have the 5.1 ohm series filament resistor to the 6AL5 discriminator. I have restored about a half dozen of these sets and four of the resistors were bad or became bad shortly after coming back to life. So be prepared if you loose sound to first look to see if the 5.1 ohm is bad.

[Chris K]

Originally Posted by Penthode

Is that an invert button beneath the volts/div control?

It says waveform off

[Chris K]

Originally Posted by Penthode

And can you reduce the sweep speed slightly on the generator (little knob on the lower right from panel) so that the photos show a bright clear display for us?

And I should add that on late 40's RCA TVs, almost all have the 5.1 ohm series filament resistor to the 6AL5 discriminator. I have restored about a half dozen of these sets and four of the resistors were bad or became bad shortly after coming back to life. So be prepared if you loose sound to first look to see if the 5.1 ohm is bad.

I will check the resistor. I tried changing the sweep rate on the 8601 and took a series of photos...they were worse

[Chris K]

About as good as I can get

[Chris K]

Manipulated the photo a bit