Many 1920s TRF radios use 4-pin '01A tubes. Most of the tube sockets use the tiny side pin on the tube base to hold the tube in the socket - with tension between the tips of the four pins and the brass tabs inside the socket.

It's a bad socket design - much less reliable than modern sockets that have a wiper that contacts the side of the pin. TRFs are plagued by poor contact of the tubes in their sockets. You learn to keep wiggling tubes to keep the radio playing.

It's tempting to try to bend up the brass tabs in the socket, but that can result in breakage.

The basic problem seems to be that the single side pin on the tube's base causes the tube to be slightly cocked in the socket. The side pin is located between Pins 2 and 3 (plate and grid). Those two pins usually make good contact.

The opposite side of the tube is often visibly cocked up, causing loss of contact on Pins 1 or 4 (filament/cathode).

Here's an easy fix: make the filament pins just a hair longer than the other two pins. This compensates for the cocking of the tube in the socket.

Hold the tube's base in a vise and heat one of the filament pins with a soldering iron. Holding a brass nail in a pair of snipe-nosed pliers, insert the nail into the end of the hollow pin, with just the head protruding. Repeat for the other filament pin.

The extra length of the nail heads is just enough to compensate for the cocking and to improve electrical contact. The nail head, if it's small enough, won't interfere with using the tube in a modern tube socket.

The nails that I use are brass "escutheon pins," 1/2" x 18, which can be soldered. Available at my ACE Hardware.

:Many 1920s TRF radios use 4-pin '01A tubes. Most of the tube sockets use the tiny side pin on the tube base to hold the tube in the socket - with tension between the tips of the four pins and the brass tabs inside the socket.
:
:It's a bad socket design - much less reliable than modern sockets that have a wiper that contacts the side of the pin. TRFs are plagued by poor contact of the tubes in their sockets. You learn to keep
wiggling tubes to keep the radio playing.
Doug, why not drop that in the hint/kinks on Antique Radios? Its good and simple fix. PL
:It's tempting to try to bend up the brass tabs in the socket, but that can result in breakage.
:
:The basic problem seems to be that the single side pin on the tube's base causes the tube to be slightly cocked in the socket. The side pin is located between Pins 2 and 3 (plate and grid). Those two pins usually make good contact.
:
:The opposite side of the tube is often visibly cocked up, causing loss of contact on Pins 1 or 4 (filament/cathode).
:
:Here's an easy fix: make the filament pins just a hair longer than the other two pins. This compensates for the cocking of the tube in the socket.
:
:Hold the tube's base in a vise and heat one of the filament pins with a soldering iron. Holding a brass nail in a pair of snipe-nosed pliers, insert the nail into the end of the hollow pin, with just the head protruding. Repeat for the other filament pin.
:
:The extra length of the nail heads is just enough to compensate for the cocking and to improve electrical contact. The nail head, if it's small enough, won't interfere with using the tube in a modern tube socket.
:
:The nails that I use are brass "escutheon pins," 1/2" x 18, which can be soldered. Available at my ACE Hardware.