Poor receive with a the R-27's or 68-R Browning's

The R27, along with the R2700 and early production of the 68-R all share one fatal weakness. You'll notice that the tuneable RF/IF transformers do not have a hollow tuning slug with a six-sided hole. They have a solid core with a screwdriver-tip sized slot visible through top and bottom holes. This type of component was called "K-Tran". A high-performance, high-tech part in 1965, but a pain in the neck in 2005. Bottom line: they fail. Always. Not if, just when.

Sometimes, one of the tuning cores will appear to "peak"correctly, and then the receiver sensitivity will fall. Now the same slug peaks in a different position. Or it fluctuates when the tuning tool touches the rim of the lower-side hole.

What made the K-Tran so high-tech was that it has built-in mica capacitors inside the plastic base insulator. Since these capacitors had a lot of metal in them, their resistance is quite low. This makes the "peak" of this kind of coil particularly sharp. Since these built-in capacitors have a lot of material in them, they tend to be stable, and won't drift a lot. Not when they're new.

The fatal flaw is the polystyrene plastic used to make the base insulator. It will shrink and become brittle with age. Styrene just does that. There is a tension spring under the brass rivet you see in the lower-side adjustment hole. This spring holds the plates of those built-in mica capacitors tightly together. Until the styrene shrinks and fractures. Then the capacitors shift around, and often drift so far that the tuning slugs will no longer show a proper peak when you tune them.

There are no easy or cheap solutions. Replacing every one of the seven dual-slug tuned "cans" is an expensive pain in the neck. Taking them apart, removing the internal capacitor parts, and soldering a disc in their place is like repairing a wristwatch. Drilling out that brass rivet in the bottom is hard to do without softening or breaking the polystyrene plastic base insulator.

One by one remove each tube, use an old toothbrush to scrub the pins with generic window cleaner and dry them off. This will remove oxides and tobacco tar, if any has built up inside. Squirt a "non-reside" contact cleaner into the socket, and work the tube around gently before it evaporates. This will serve to help cut through a layer of oxide on the socket's contacts. Think about it. If there's enough contamination on the tube pins to matter, the sockets are probably just as "noisy".

The front panel controls and the S-meter zero pot should each get a shot of "Control cleaner", one that contains a silicone lubricant. If the RF Gain control won't turn all the way down to zero ohms, the receiver won't deliver full sensitivity.

That receiver tends to be an expensive one to bring back to life. At some 'awkward' age, any radio will go from a "repair" item to a "restore" item if you want the original performance from it. Best of my recollection, it was around 20 years for that one. About 20 years ago.

The electrolytic capacitors are famous for appearing okay, but only for the first week or month you run the unit. When you replaced C62, you were just getting started. All the other electrolytic's in the radio will have to go if you plan to operate the receiver for much longer. Those parts were never meant to last 20 years, let alone 40.

Pulling out the 0B2 regulator tube only makes a noticeable difference when the radio is below-par to start. It serves to hold the voltage on the oscillator circuits constant. Reduces dial drift. Pulling it out causes the operating voltage to parts of the receiver to rise by 40 or 50 Volts. This sounds as if it has improved the receiver's performance. It's an illusion. What this tells you is that the receiver's sensitivity is crippled. Pull it from a receiver that's working right, and you'll hear only a minor difference.