Back to the work...
The next thing I did was to make a couple resistance checks to rule out an open flyback transformer or vertical output transformer. The flyback is simple to check, with a simple resistance measurement between the plate cap leads of the 6BG6 horizontal output tube and the 1B3 HV rectifier tube. This portion of the winding measured spot on the 240 ohms called out on the schematic, and the other windings checked out as well. Same for the vertical output transformer, and the deflection yoke windings. I like to check these major components (and the CRT) at this point before putting a lot of time and new components into a set, just to discover a "showstopper" in the form of a defective part which is not easily available. For this particular set, I have a fairly complete parts chassis kicking around, so even a bad flyback wouldn't be that big of a problem.
Another common failure point on RCA-type designs of this era are the large power resistors used in the LV power supply voltage divider network. These resistors are mounted inside a sheet metal box on the rear chassis apron, with openings at top and bottom to promote convection cooling. Opening the resistor box found everything physically pristine, but both sections of the large wirewound resistor R153 were found to be open. I suspect that this is a corrosion induced type of failure from decades in storage, rather than a burnout from excessive dissipation, as no shorts were seen on any of the power supply rails. I will save the failed resistor and do a teardown/failure analysis later. This resistor had already been grabbed from my parts donor chassis for a previous project, so modern replacements were called for. Because the 2 sections of the resistor were both odd values (1125 ohms and 610 ohms), I used 25W adjustable resistors from Ohmite (210 series). The units I installed were 1250 and 750 ohms total, and I adjusted the metal slider bands to get the precise values I needed. Both new resistors stacked nicely end to end on the original mounting bolt, using the new washers that came with them. I put some heatshrink over the unused resistor lugs to prevent shorts. Ended up with a very clean installation.
Before and after pics below. Fortunately, the lower "candohm" resistor (R154) in the box checked good on all sections. These are a bit more difficult to replace when defective. I usually use metal jacketed chassis mount types here when needed.
Next on the agenda were the electrolytic caps. Normally, I might try installing a rectifier and bringing the power up very slowly in hopes of "reforming" the electrolytics at least long enough to see if the set shows any signs of life. But a close look at the caps in this set showed definite signs of crusty electrolyte leakage from a few of them, so I just dove in and began replacing them all. There are 13 electrolytic caps in the set in total, with 12 of them housed inside 5 "twist lock" chassis mounted aluminum cans. Each can houses 2 or 3 sections, with the common negative terminals connected to the metal can itself. In most sets, the can is connected directly to the chassis for a ground connection. In this set, however, none of the negative terminals are actually at chassis ground potential, with most being at -85V with respect to the chassis. They are mounted on phenolic insulating plates, and covered with cardboard insulating sleeves to prevent a shock hazard.
You have several options when replacing twist lock capacitors in vintage gear. A very few values are still being manufactured, mostly ones used in vintage tube stereo gear. They cost $$$, though, and weren't available in the values I needed here. Another option is to disconnect the old cans completely, and tack in newer radial electrolytics under the chassis as needed. I tend to avoid this as it looks messy, and can get quite cramped in some areas.
The standard technique is to remove the old can capacitor, uncrimp the base, pull out the old guts, and install the new capacitors inside the old can before recrimping and reinstalling it. This gives an original appearance when the cans are exposed above the chassis, but is very labor intensive.
Because the aluminum cans are covered by the cardboard sleeves on this set, It allows me to save a LOT of time by not uncrimping and recrimping the cans and pulling out the old capacitor sections, but simply cutting them open above the base crimp, and discarding the upper portion of the can and the old contents. The new capacitors get installed in the old can bases, with the leads threaded through holes drilled in the base wafers, and soldered to the lugs under the chassis. The cardboard sleeves can then be reinstalled over the new caps, hiding them completely.
I begin by unsoldering all the connections under the chassis, making notes of where all the wires go. then the mounting lugs can be straightened out and the cap carefully wiggled free of the chassis, being careful not to break the phenolic insulator. Once the cap is loose, I roll it firmly with my palm on a hard surface, to break the glue bond (some kind of varnish) between the cardboard sleeve and the aluminum can. The sleeve will then easily slide off in one undamaged piece, and gets set aside for reinstallation later.
I use a Dremel tool and a fine toothed circular saw blade to cut all the way around the aluminum can just above the base crimp. Then the upper section of the can can be pried away from the base, and the internal connections cut off flush with the inside of the base. I clean out any loose residue inside the base at this point, then drill a 1/16" hole next to each lug and an additional hole next to one of the mounting ears for the ground connection.
I use Nichicon or Rubycon 105C rated radial electrolytics to replace the old caps. No need for ultra low ESR caps in old gear, but sometimes they come in tall skinny form factors which can help fit multiple caps inside the old cans. I connect all the negative terminals together to a single lead that passes through the base wafer, along with all the positive leads, which connect to the corresponding lugs on the old base.
The base/capacitor assembly can then be reinstalled like a new twistlock. Make sure that the leads coming from the new caps get soldered to the lugs along with the rest of the wiring. If the wiring under the chassis is very hard to access, it is possible to use this technique without removing the can completely from the chassis, if you have access to cut the can off above the chassis and drill the lead holes.
The pictures show what the rebuilt capacitors look like before the cardboard sleeves get put back on. There is one axial electrolytic (C160) under the chassis that also gets replaced at this point.
Next up, applying power and seeing if we have any signs of life from the set at this point....