Front Panel Embellishments

The final touches on the front panel were installed today.  Dial markers were added just above the BFO, RF gain, and crystal filter phasing control knobs.  The markers were made by filing down the heads of #2-56 screws.  These are similar to the dial markers used on the National HRO series receivers.

Next, an information tag and main tuning calibration chart were added.  The hi-resolution (300dpi) graphics were created in GIMP (GNU Image Manipulation Program).  The calibration charts (160, 80, 40, 20) were modelled after the early HRO style paper charts that were on the plugin coilsets, with a 0.1 in. grid.  In fact, the satin-black metal frames and clear plastic covers (yellowed from age) to mount the information tag and calibration chart were taken from an old HRO coilset.  The frames are held in place with #4-40 black screws.  The front panel has tapped holes to accept the screws.  When changing bands, the calibration chart above the main tuning dial can be changed by removing the top screws and loosening the bottom screws.  The charts can be slide in and out from the top.

The yellowing of the plastic  covers really adds a nostalgic appearance to the receiver.

With all of the front panel work complete, it’s time to start wiring!

Power Cable, Cabinet, Front Panel…

Power Cable

I was able to procure a vintage brown cloth covered, 6-conductor power cable.  Two(2) of the conductors are #14, adequate for the filament current if I decide to use 2.5V tubes (approx 11A including dial lamps).  Only two of the smaller gauge conductors will be used for B+ and B- (ground).  The cable is fed through a hole with rubber grommet in the rear and held in place with a metal cable clamp inside the chassis.Continue reading …..

Crystal Filter

The crystal filter unit came from a parted HRO-7.  It is essentially the same circuit as that of a late model HRO-5TA1 with a 6-position selectivity switch and variable phasing control; earlier HROs (and FB-7 superhet) had a variable capacitor for selectivity control instead of discretely switched selectivity.

As with the BFO and IF cans, the crystal filter unit was disassembled to replace the original leads with cloth covered wire.  Those exiting below the chassis Continue reading …..