Early RCA Horizontal Circuitry...Help!
 

https://imagizer.imageshack.com/v2/1...922/tbVrsr.jpg

I guess what I'm looking for is some education regarding the horizontal circuitry in the KCS 47 and what all these things do and how they do it. In this one circuit there's a horizontal frequency, horizontal drive, horizontal waveform, horizontal linearity and width adjustments plus the horizontal hold control not shown here. So the 6SN7 puts out the oscillating frequency that's tuned to 15.75 Kc by the adjustable coil for horizontal frequency. That's a sawtooth shaped wave right? It's modified to a double peaked wave where the waveform adjustment lets you tune that shape to where those two peaks are of equal amplitude correct? I guess I'll stop there and try to figure out how this all happens and why. I know only very, very basic vacuum tube operating theory. The tube produces the oscillating waveform that comes out as a sawtooth. The oscillation comes out of the plate, goes through the coil and back to the screen to do what, set the on/off timing of the screen gating the electrons from the cathode to the plate? What is the 180pF capacitor doing for this? I guess what I'm asking is how does this loop produce the 15.75Kc oscillating frequency and keep it stable???

Really admitting my ignorance here but, believe it or not, I am a scientist/biologist professor and I need to know how things work at the most basic origins. Electricity absolutely baffles me. It took a lot of explaining to get me to understand how AC works when there's no net movement of electrons in the wire!!!!!

Oh boy. Short answer is any oscillator is a tuned circuit and requires feedback. The 180pf provides some feedback from the tubes plate circuit to the grid circuit. The adjustments are, for the most part, self evident as they are named, they do as implied.

As far as theory of operation you may be best off reading a service text from the period of the set you're working on. I agree it's really difficult to understand these circuits without building from a very basic and fundamental understanding of circuit concepts. To jump in feet first trying to understand TV circuits, is about impossible. For TV specifics I'll recommend Grob Basic Television 1st or 2nd edition, and Milton Kiver Television and FM receiver servicing 1st-4th editions should be fine. But if for instance you don't have a firm grasp of Ohms law and how voltage division happens in both DC and AC circuits, even these basic TV books will be difficult to understand. Honestly you need to be seriously interested, dedicated, and self driven to learn any electrons theory.

I actually have those texts among others from the era. I do understand Ohms law and DC circuitry to an extent. What do you mean by voltage division? That sounds simple enough but I'm sure there's more to it than that! DC circuitry is easier for me because it's directional and flowing. What is the oscillating frequency coming out of the oscillator?

By voltage division, I mean how the various electrical and electronic components react to both AC and DC current, and how voltage influences current flow. A starting point is to understand how to calculate DC voltage drops across both series and parallel resistances. Once you can do that you can at least follow how the power supplies divide voltage and distribute power to the various circuits.

Do you mean the additive effect of resistors in series vs the overall resistance in a parallel circuit being a value between the hi and low resistor values? I think I understand that however getting parallel resistance right when you're trying to get a resistance value for a resistor you don't have is a bit harder. I use the online calculators and an educated guess then go by some trial and error to get close enough. Is this what you mean Kevin?

Yes but also how the voltage across, and current through, is calculated. But you have the first part. :thmbsp:

I'll stop this soon because VK is no place for electrical theory. I get the hydraulic analogy where V=Pressure, I=Current (amps) and R=resistance or constriction in flow. So if voltage is overall pressure on one side of the divider and coming out of a rectifier tube at 300V DC at 2.0 amps and it encounters parallel resistors one at 1K and the second at 500 ohms, obviously more current will flow through the 500 ohm than the 1K. But I don't see how you calculate the voltage in the 2 circuits after the resistors unless I'm thinking about the mathematics of this all wrong.

As you say, across two parallel resistors the current divides between them, but the voltage drop across any parallel combination is the same. In your analogy you could define the voltage from the rectifier as a constant, and the current draw from the supply is subject to change dependent on the total resistance load. When you combine multiple parallel loads in series they each form their own voltage drop according.

OK got that. Back to my horizontal circuit, specifically the width control and how it influences the horizontal deflection. The yoke is a big electromagnet that bends the electron beam scan using the horizontal windings to deflect the electrons side to side. The vertical yoke when electrified and magnetized determines where the scan starts positionally at the top of the phosphor screen and where it finishes on the bottom. Does the width control, as a variable resistor, potentiate the voltage to the horizontal yoke windings and is deflection left to right dependent on the strength of the voltage induced magnetic strength? It doesn't look to me like it's directly connected (I'll post a better picture tonight) to anything going to the yoke. I understand the role of the permanent magnets, ion traps and electromagnetic focus coils in other TVs providing additional nudges to the beam.

The forum has been so flaky I can hardly get a post in today.

That width control appears to be varying the screen voltage of the Horizontal output tube, and probably determines how long it conducts for the right portion of the scan.

Same here....Service Unavailable

It also adjusts the B+ going the the horizontal hold control. It's not a conventional circuit because of the direct drive yoke configuration.

On my KCS40 chassis they actually do have the resistive width control in series with the horizontal yoke winding. Same basic direct drive circuit, but more than one way to skin a cat!

Direct drive yoke?

This site is very unstable today like you said. I hope we're not on the verge of another crash.

More on the synchroguide circuit here:
http://rca.vobj.org/RCA%20Engineer/R...ignHistory.pdf

The horizontal yoke winding is directly driven by the plate circuit of the horizontal output using that odd looking air core auto-transformer. Conventional flyback transformers up to that point used a isolated secondary winding.

Ok I’ll need to examine the schematic and look in the HV cage at its condition. BTW I built the yoke housing support you showed and tomorrow I’m going to bring up the unrestored chassis on either a dim bulb progression or on my Sencore isolation transformer/Variac to see if it produces anything on the 5” tube. After that, I think I’ll try doing it with the restored chassis and see if I can figure out what to do for the video/sound misalignment. If I can replicate your bench top rig without blowing 15KV across my chest and heart I think I should be able to align it. I have test sockets for all of the tube pinouts so working under the chassis should be at a minimum.

Always use the one hand rule while probing high voltages. Keep your other hand away from anything grounded and stand on an insulated surface if you're on a cement slab. If your uncomfortable or accident prone wear insulating gloves. These chassis rest quite comfortably on their side against the high voltage cage so you can navigate both sides. You need to somehow fix the 5AXP4 in the yoke so it's not moving around. You can see in my photo there's a plastic insulated clamp with an aluminum band holding it against the yoke. I don't know of any source for such a clamp and I believe that came with one of my test crts.

I finished getting the rig setup and it fits on the chassis just fine. I found a loose HV anode cable and soldered two alligator clips together back-to-back to finish the connection from the cage to the 5AXP4. I wish I had a small metalworking lathe so I could turn a custom connector. This anode wire at the cage end is not bare wired rather, it has a socket on the end just like the HV connector on the RCA chassis. Can't remember where I got it but it must have been from a TV with an unconventional anode HV cage connector or it's an anode extender for powering a CRT further from a chassis. The forked end that connects to the CRT fits firmly in the other end of the wire so a fork terminated anode from a TV's HV output can connect to it giving you another 18" of travel. I think my setup is about as safe as can be on one of these metal CRT TVs.

Do a query on "Synchroguide". If you can find the Jack Darr book on servicing television horizontal circuits, that has a great explination of how to adjust this circuit. (Start by jumpering the waveform coil)

For the more esoteric description, see: http://rca.vobj.org/RCA%20Engineer/R...ignHistory.pdf

Thanks for the heads up! The flyback in the unrestored TV is open on the primary side between test points 2 and 3. If I measure continuity between 1 and 2, it's fine but it's open between 2-3 and 1 and 3. The ETF says it has one, part #75519, but who knows if they'll be able to find it.

Sent you a pm.