[Milsurplus] BC-659 Fun and Games

[John Vendely]

Howdy Steve,

Socket corrosion can be a problem, but often these intermittents are 
caused by improper tube removal technique.  Few people today are aware 
that removing a loctal tube from its socket must be done in a specific 
manner to avoid damaging both tube and socket.   The typical practice of 
pulling the tube vertically from the socket while wiggling it around is 
incorrect.  This causes permanent damage to the socket locking 
mechanism and causes the familiar looseness and intermittent problems 
you describe.   It can also break the tube seals.

The metal loctal tube base features a small "bump".  The tube should be 
carefully tilted slightly in the direction of the bump and pulled from 
the socket while tilted.  Only modest force should be needed to extract 
the tube.

Loctal tubes rely on the locking action of the base to hold them in 
place.  Once the damage is done the tube may not remain properly seated 
and intermittents set in.  Sometimes the only solution is to replace the 
socket.  So many have been trashed over the years that it can be 
difficult to find good replacements...

73,

John K9WT

On 7/5/2026 12:29 PM, sbjohnston--- via Milsurplus wrote:
> I've seen a lot of early two-way radios from Motorola that used the 
> loctal tubes.
>
> Loctals were also used in quite a few models of commercial table- and 
> portable-broadcast receivers.
>
> My experience with repairing/restoring broadcast and shortwave radios 
> that used loctals is that about 25% of the tubes/sockets become 
> troublesome (at least one bad pin-to-socket connection in a quarter of 
> the tubes). The result is a lot of wiggling of tubes in their sockets 
> trying to get stable operation. Deoxit helps but is not a complete 
> answer to this particular problem.
>
> I've always wondered if the choice of metals or plating for the pins 
> and/or the socket contacts is the problem.  Maybe dissimilar metals 
> touching for years creates a difficult corrosion issue?
>
> The loctal pins look like the same sort that were used in 7 and 9 pin 
> miniature tubes but maybe the socket contacts are different?  I recall 
> the loctals look like like they have less contact area and are like 
> scissors biting the pin whereas the miniatures' socket contacts are 
> wiping the pings with longer springy tabs.
>
>
> Steve WD8DAS
>
> sbjohnston at aol.com
> http://www.wd8das.net/
> http://af4k-crystals.com/
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