HRO MX update 3

Whilst checking components above the chassis, I noticed that the connections to the Local Oscillator coil have been modified.

One of the coil contacts was originally connected to a capacitor mounted on a ceramic insulator on the chassis. I believe that this provides temperature compensation.

This connection has been broken, and in its place are an additional inductor and variable capacitor below the chassis. These form a series tuned circuit between the coil connection and ground.

I've no idea what the purpose of this modification might be, and a quick search on the web didn't turn up anything relevant. I somehow doubt that it's an 'official' modification though.

I'm tempted to remove it and restore the the original circuit, but I think I'll do a bit more research first.

Update: Having failed to find any info on the modification, I decided to remove it and restore the original wiring. 

Keep listening!