Plenty of spare leads were added to the pickup leads and provided to the output jack.  Here the output lead is connected to a gray guitar coil cord with alligator clips, going to an amp to test the electronics.

This picture and following pics of the electronic harness from different angles, provide good views of the color coded wiring for comparison with the schematic.
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1953 Valco El Grande Steel Guitar
Customer's Work Progress Reports

~ Page 12;  Electronics Reassembled ~

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Plenty of spare leads were added to the pickup leads and provided to the output jack.  Here the output lead is connected to a gray guitar coil cord with alligator clips, going to an amp to test the electronics.

This picture and following pics of the electronic harness from different angles, provide good views of the color coded wiring for comparison with the schematic.
Here are both the real magnets (2 on the left) and an iron slug faux magnet (3rd from left) and a wood slug faux magnet (far right).  The pickup will operate with only 1 magnet and lower end Valcos had a faux slug magnet;  But the pickup works much better with 2 magnets.  This Steel had 1 magnet but a second magnet will be added after both magnets are recharged.
Here's a good trick.  Shown below is a volume control built into a project box.  It is wired just like a guitar volume control.  I use this box as a volume control when testing a guitar in an amp.  A cord runs from the guitar to this box, and out of this box to the amp.  Not only is it great to be able to control volume for different tests, but you can also turn the volume all the way down rather than removing the cord from the work when periodically needed.
NOTICE:  The wiring shown on this page is incorrect, ...and correct wiring will be shown as soon as it is accomplished.  The wiring shown on this page is being temporarily kept posted here for the archive of the work on this Steel.