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

[Penthode]

Try increasing now the x gain to fill more horizontally the screen.

Congratulations. That looks much better now.

[Penthode]

To invert the x channel so the sweep is correct from left to right, select the Vertical menu and select INV.

[Chris K]

Not only is the scope new but I’m using a high quality and new TEKTRONIX probe. That could account for the difference in quality. Are we fairly certain this reversal is a scope setting issue or could the discriminator somehow be tuned to produce this? Does it make sense to replace all the resistors and ceramic caps in this area of the chassis? I know these stone caps rarely fail but you never know. I can’t find anything yet on the scope that suggests the horizontal polarity is being rotated out of phase to this degree.

[Chris K]

I did invert it and the trace looks like it’s supposed to but the frequency scale is reversed. They increase right to left

[Penthode]

Originally Posted by Chris K

I did invert it and the trace looks like it’s supposed to but the frequency scale is reversed. They increase right to left

I am then confused. If the frequency increase was originally from left to right, then the y axis must be inverted. Try reversing the inversion on the x axis and apply it to the y axis.

The detector in the receiver is often going to invert. It won't make any difference to the operation so long as it is a symetrical S and the slope in the center of the S is linear. It is only the way we are viewing it.

[Penthode]

When I restore a set, I replace only what is necessary: electrolytics that fail to restore, paper capacitors that have a high DC potential across where leakage will cause a problem. I leave the resistors until I fire the set up and the analyse the performance. Eg narrow width could be the dropping resistor feeding the horizontal oscillator. I have lots of new old stock carbon composition resistors I replace the originals with.

And I try to wire it as if no one has been there since manufacture. (The only difference is the capacitor appearce between the old paper and newer metal film. Resistors look the same except for the added or improved tolerance band). Even if the resistor is slightly out of tolerance, so long as it does not affect performance, I will leave it.

[Penthode]

I know others disagree with my approach, but if the electroytics have not been abused eg powering up the set after decades of in activity, I try to retain the original electrolytics. Of the five pre-1950 RCA televisions in my possession, I have had to replace only two electrolytic cans. The rest survived. I do give the set an extended bench test to confirm all is well and if there is any doubt, I would replace it.

My 1947 RCA 721TS I restored four years ago is used regularly and retains all of it's original electrolytics. I bought the set in around 2015 and the previous owner said the set was retired in about 1960 to his parents attic and had not been powered in 55 years. I carefully and slowly reformed each electrolytic capacitor and replaced only the paper capacitors I deemed necessary before powering up. I don't use series light bulbs or variacs. When the the time comes "wham" on goes the power. I check, recheck and check again everything before the first power and I have never had a set in the last 40 years explode in my face. (I first worked on your chassis in 1969).

[jr_tech]

Originally Posted by Penthode

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

Channel invert is accessible through the menu selection button.

https://w140.com/tekwiki/wiki/TAS465
jr

[Chris K]

Thanks guys…be back on it tomorrow night! Glad I’m working with more reliable equipment!

[Penthode]

Originally Posted by jr_tech

Channel invert is accessible through the menu selection button.

jr

Found it in the menu. Trouble was the x channels did not require inversion but the y channel did in order to match the service notes picture.

[Chris K]

Originally Posted by Penthode

I know others disagree with my approach, but if the electroytics have not been abused eg powering up the set after decades of in activity, I try to retain the original electrolytics. Of the five pre-1950 RCA televisions in my possession, I have had to replace only two electrolytic cans. The rest survived. I do give the set an extended bench test to confirm all is well and if there is any doubt, I would replace it.

My 1947 RCA 721TS I restored four years ago is used regularly and retains all of it's original electrolytics. I bought the set in around 2015 and the previous owner said the set was retired in about 1960 to his parents attic and had not been powered in 55 years. I carefully and slowly reformed each electrolytic capacitor and replaced only the paper capacitors I deemed necessary before powering up. I don't use series light bulbs or variacs. When the the time comes "wham" on goes the power. I check, recheck and check again everything before the first power and I have never had a set in the last 40 years explode in my face. (I first worked on your chassis in 1969).

I have a 721TS that I restored about 3 years ago that had an original stand. I was owned by one family as well and I bought it from a couple who were retiring and downsizing. One of them told me she remembered the day her father brought the TV home and although it stopped working in the late 1970s, it had remained a fixture in their living room until she inherited it. They cared for it as lovingly as her dad did and I was lucky to get it for around $135! I restored it, not with respect for original parts but with new components. It hasn't been turned on in a couple of years. I'll get back to it one of these days.

[Penthode]

Originally Posted by Chris K

I have a 721TS that I restored about 3 years ago that had an original stand. I was owned by one family as well and I bought it from a couple who were retiring and downsizing. One of them told me she remembered the day her father brought the TV home and although it stopped working in the late 1970s, it had remained a fixture in their living room until she inherited it. They cared for it as lovingly as her dad did and I was lucky to get it for around $135! I restored it, not with respect for original parts but with new components. It hasn't been turned on in a couple of years. I'll get back to it one of these days.

That was a great deal for something lovingly preserved! I am very happy with the 721TS as it is relatively compact and is a a good although somewhat archaric performer with split sound and no AGC.

[Chris K]

Photo as best as possible but the trace is equally bright all the way through. I did invert the vertical. What do you all think? Is it time to move to the next step?

[Chris K]

Doesn't get better than this...in the shop watching the Eagles' season opener on my Admiral Bakelite Baby!

[Penthode]

Originally Posted by Chris K

Photo as best as possible but the trace is equally bright all the way through. I did invert the vertical. What do you all think? Is it time to move to the next step?

Yes looking good. Although you could on the 8601a increase the sweep width a bit (there is a vernier adjustment), then increase the x gain on the scope to get a more complete display.

Then adjust T113 top until you get a symmetrical S curve. Then let's move on!