The SCR-506 was mounted in vehicles where longer range communications were required. They were also used in ground installations usually at the battalion and higher levels. While short range tactical communications between tanks were handled by the SCR-508 system (Channelized FM), the SCR-506 was mounted in some tanks where longer range communications were necessary.

It is a misconception that the SCR-508 replaced the SCR-506. Each system had a different purpose.

Here's the BC-652A receiver (left) and the BC-653A transmitter (right):

TM_11-630 provides the specifications for both units:

This photo shows the transmitter with both cover panels installed....

...and this photo shows the transmitter with both cover panels removed.

As can be seen, the tuning mechanism has been removed. Here's the tuning mechanism and associated tuning shaft.

To re-installed the tuning mechanism, the front panel needs to be removed. This does not look to be particularly hard to do, but it gets a bit more difficult when one is trying to move a 143 pound brick around the workbench.....

The transmitter's dynamotor can be powered by the vehicle's 12V electrical system:

Some further views of the inside of the BC-653A transmitter:

As can be seen in the above photo, the receiver has been modified to use external power.

I have a DM-40 dynamotor for the receiver; since it's still bolted to its shipping platform and comes with an unused set of brushes, it has probably never been used.

Here's some photos with the dynamotor placed in the receiver. The Cinch-Jones socket would need to be “unmodified” to mate with the dynamotor plug.