[David Dunlop]

The Crystal Calibrator Panel on my Main Set Receiver was very badly scratched up, including several across some of the lettering, so I decided to replace it with the panel from my spare receiver, which had only a couple of small visible paint chips and a few larger ones around the perimeter that is hidden under the upper receiver front panel. The first three photos show the original panel, the original replacement panel, and the refurbished replacement panel. It turns out that Testors 1139 Semi-Gloss Black Model Paint is a near perfect match to the black paint Canadian Marconi used on the calibrator panel here.

The Crystal Calibrator is a complete, self-contained sub assembly that is mounted to the receiver chassis at some point on the receiver assembly line, by means of four small angle brackets, two either side of the rear chassis plate of the calibrator. See the fourth photo in this post. Swapping out the calibrator panel is, fortunately, a purely mechanical task, that is easy enough to do with a little forethought.

The first step is to lay the receiver on its left side on your bench as this makes access to all the necessary hardware much easier, and if any hardware falls loose, it will not disappear into the bottom of the main chassis. Then remove the calibrator switch knob. You should then notice this switch has a small key tab just to the left of the switch shaft that sits in a small hole in the panel just above the ‘FR’ of “FREQ CHECK”. Then, carefully unscrew the large hex nut securing the switch. It should have a large, external tooth lock washer behind it. Be gentle as this has been tightened against 75 year old paint that might have been bruised and you do not want large chips to pop off if you can avoid it.

The next step is to undo the ground terminal at the lower end of the 5 Watt 8 Ohm Lamp Resistor. Shown in the first two photos of the following post. You can then remove the two slotted, pan head self-tapping screws on the underside of the calibrator panel, shown in the third and fourth pictures of the following post.

Next remove the two screws on the upper front of the calibrator panel, above the Holders, Lamp Assembly. You can now gently pull the panel assembly forwards just enough to access the centre screw terminal on the back of the Holders, Lamp Assembly with a small socket. There is a small trick to this, however. Loosening the hex nut on the centre terminal to remove the connector also loosens the Lamp Socket inside the Holder and it will start to turn with the hex nut you are trying to remove. So before you start trying to undo the hex nut, remove the red lamp cover from the front of the Holders, Lamp and place a fingertip on the bulb inside with enough pressure backwards to hold the bulb and socket still while you undo and remove the hex nut.

To reassemble, do everything in the reverse order.

David