An archive of Synchrophase Service Data, Parts Lists, and other
I am redrawing many of the Grebe schematics. The new versions
will include voltages, part numbers, and values.
I am also creating original mechanical drawings of some components. These
will facilitate creation of modern replacements if vintage parts are not
This is an ongoing project, so check back often, and
anything you need that's not already here.
There are three documented versions of the MU-1 receiver. The early version has no "Tone Color"
control. The late version has a +135-volt battery connection which goes directly to the speaker.
The middle version has a "Tone Color" control but no +135-volt connection.
Other differences exist. The tuning capacitors were coupled using chains sometime in 1925.
An automatic bandswitching system was added to extend the tuning range. This change is
shown on the mid- and late-version schematics, so it was in use by August of 1925.