Type 76 Receiver Refurbishment

 I'm not sure exactly how far to take this refurbishment work because I don't have plans to resurrect a complete Four Square system. I'll probably check out the RF performance of this set which comprises just an RF front-end up to the IF transformer feeding the IF amplifier. At this stage I don't even know the details of the intermediate frequency output. That will become evident during testing. The main tasks are to clean up the mechanical parts especially sorting out chassis defects and cleaning the dial. The initial task is to straighten the bent centre section of the chassis. I measured the overall size of the chassis and found it was square so it's just the centre section, resulting in the effects below, that needs fixing.

 

 

 Left, the leaning RF coil and above, the dog-legged tuning coupler.

 

 First, one side: The worst damage was under the relay. I used a furniture cramp and gently applied pressure until the centre chassis section was a little over-straightened and ready to spring back slightly.

 

 I gauged the correct amount of straightening by watching the tuning condenser coupler, then released the cramp and repeated the exercise on the other side of the chassis.

 

 In this case the aerial tuning coil went from leaning over to vertical, and after removing the cramp the chassis was no longer distorted and the weird dog-leg in the coupler had disappeared.

 

 At present the dial markings behind the front panel are obscured by muck and the mechanism slips badly. Clearly the first job is to remove the front panel. Tentative attempts proved that a freeing oil was needed and after applying this I removed two screws at the top of the panel which used captive nuts. The lower fixings were through the handle and needed a 4BA nut spinner to detach the nuts. Then the three knobs which had decent-sized grub screws which slackened easily.

 

 

 Above are the few parts needing to be removed to detach the front panel. The aluminium disk has a couple of pins which locate in holes on the tuning spindle locking bush. Notches point to the 0-180 fine tuning scale.

 The panel then just lifted off revealing debris collected over 75 years, but nothing serious and a very interesting method of increasing scale length.
 

 

 The rear of the front panel showing the simple locking mechanism and an opaque tuning window.

Below are the dial locking parts. A lever on the front panel operates a cam which closes the circular jaws around the knurled part of the tuning shaft.

 

 

 

 On the left you can just see the QA stamp for E.K.Cole indicating at least the front panel was made by Ekco.

Below is a second, much clearer QA stamp, this time on the chassis.

And the mod record plate.

 

 

 

 Above is the cleaned up and partly reassembled dial showing the clever method of extending the calibration scales. A small shaped-plastic marker held by the transparent fixed cursor is fixed horizontally in place but the spiral slot cut in the dial makes the marker move vertically so you can see the correct frequency. To prevent damage to the plastic marker there are two metal tabs rotating with the tuning spindle and moving in such a way that they lock the dial at each extreme of rotation.

 

 

 Left, the cursor parts including the broken marker and above the new marker compared with the original. The marker is curved to fit in the dial slot and I cut the new one from part of a plastic bottle where the curvature matched the broken marker. The designer even added a phosphor bronze bush to the cursor to prevent wear.

 

pending

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