New Project RCA 16t152 Trying to learn to troubleshoot better

[Aperna1985]

I picked up a 16T152 for $25. I brought it up on a dim bulb and after playing with the high voltage tubes it came on. There was a little hum in the audio. I didn't have full horizontal or vertical deflection. The set will get a full recap, but like my last RCA I want to go section by section to try and learn from the failures. So first I want to repair it.the chassis is a KCS-47E. I figure let's go after the vertical first. It uses a 6SN7-GT for the vertical oscillator and sync amp. The output of pin 2 goes through the vertical oscillator transformer then comes out and goes to the height control. Coming off there are 2 caps that go to the grid of the vertical output tube. I'm guessing this is where I should start? Or should I be looking at the section of the tube that feeds the primary side of the oscillator transformer? This side effects the vertical hold control.

Also I attached a picture of what the picture looks like now. This is at line voltage, no bulb.

Here is a link to the schematic on the ETV museum website.

https://www.earlytelevision.org/pdf/...edata-1951.pdf

[bandersen]

More likely power supply if both vertical and horizontal are shrunk. Are you still using a dim bulb setup? That might be restricting power to the set.

[Username1]

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If you have a hum in the audio, then 100% You have bad filter caps in the power supply
that is the place to start. As a matter of fact, whenever you or anyone has a problem
with any tv, start with the ps and be sure it's 100% working within spec.


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[MuzzcoVW]

X3 on the power supply. You have more luxury of easily search and destroying problems on that set. The Philcos I'm working on it's not at all convenient to do so. I would replace any electrolytics before I did anything. Why mess with them at all?

[zeno]

Dittos on PS first.
After that the HV/hoz. Then vert, IF's, tuner etc.
Best to learn the block diagram, just knowing that will speed repairs up

Zeno

[Aperna1985]

I intend to check the main filters. I haven't had a chance to check yet. I only spent about 20 minutes just seeing if I had anything to work with.
But thanks I always looked at the horizontal and vertical as 2 separate systems, rather than being intermingled. I will follow the block diagram like Zeno said.

[MuzzcoVW]

I agree following the block diagram was taught to me by my mentor years ago, it makes things so much easier when you can visualize the specific areas. IMO I wouldn't even check the filters, just replace. They're going to have to go anyway so...

[bandersen]

Part of the vertical circuit is usually powered by a boost voltage that comes from the horizontal circuit.
There is also often a lower B+ voltage derived from the audio output amp.
I can be difficult to just work on one specific circuit and get it to work perfectly,

[Penthode]

I would have to question why anyone would want to do a dim bulb investigation on an unknown set of 1950 vintage? As the set has been retired for decades, firing it up could do a lot of damage.

Ah yes you may say that it will give the electrolytics a chance to reform. This is the point I have tried to make repeatedly that if you refrain from powering it up and carefully analyse separately and in a controlled manner reform the electrolytic dielectric, there is a good chance they will survive. I have saved at least 80% of the original electrolytics in that way as well as transformers, resistors and tubes destroyed by leaky paper capacitors.

Maybe the dim bulb business could be used on post 1965 sets since by that time paper dielectric capacitors were essentially obsolete. On the otherhand what is the point of powering it up before you have completed at least a good visual evealuation of the set with the chassis pulled?

I welcome other opinions for and against.

[Kevin Kuehn]

This TV is one of RCA's early and unusual Direct Drive horizontal output designs. Basically an auto transformer directly driving the horizontal yoke winding. They work quite well when restored. And more energy efficient than the traditional flyback of the time. But the air core design only existed for a year. I believe in the second year models they added a small ferrite core, but the horz yoke winding remained in series with the high voltage winding.

[edit] Looking at the schematic this does appear to be the second version with the small metal core. But take a look at the unusual horizontal output configuration.

Here's the early and later variety. The one on the right is an air core, the left has some very small core, but I'm not exactly sure what it's made of. I'd be curious to hear what Penthode knows about these RCA Direct Drive models.