Nachtfee revival


Page initiated: 7 January 2021

Current status:   8 January 2021


Contribution: A (8 January 2021)




Hans Goulooze started first with removing the rotary converter

This motor has two functions: to supply the 135 Hz AC of ca 16 V, which is feeding the wobbling Ferraris motor at the front-end of the receiver, as well as supplying the ac voltage for driving the HT transformer; which actually is being fed onto an air-tight transformer.

On the left-hand side we notice the transmitter (TX) and the receiver (RX) sections.

On top on the right-hand-side we see the mechanical coding module; where eventually two metal keys can be inserted.



Down of the coding-module (right-hand side) we recognise a vertical shaft with a small slit; which is receiving its mechanical rotation from the 'hook-gear' attached onto the rotary converter

However, there are two open wires visible of which function we yet have no idea.  Maybe it is only to be connected onto a capacitor.  The valve top right of the mechanical coding module is type RG 12D60, and is used for the HT of the receiver as well as the driver stages of the transmitter, though excluding the anode voltage of the LS 50 transmitter stage.

In our perception,  it would be practical to compare the situation existing in our functioning FuG 25a.



Four wires: number 1 and 2 being used for the supplying 24 V dc; the other two are providing ca 16 V 135 Hz ac

The small shaft up is feeding the coding mechanism. 



The transparent sheet has to be used for re-establishing (remake) the various Al cover-plates; as it is always quite delicate to determine exactly where the many 3 mm screw-hole should be drilled



Hans is demounting the hook-gear arrangement, as to get access to the 'hampering' tiny driving (feeding) shaft




When you see it, those used with detaching such a tiny clutch will acknowledge that it is quite likely that he motor-shaft-end will likely be bended!

Please look carefully: maybe you recognise that there exist two dots. Of which one is a tiny conical rot fitting the clutch onto the driving shaft.

However, the second dot is ceiling off the fixation of the clutch onto the tiny driving shaft.

The nuisance we encounter here, is, that inside the motor collector is reaching inside the Bakelite top plate, keeping the bearing inaccessible. 

Hans found, nevertheless a means to get some lubrication inside the invisible bearing.


With a bended 'injection-needle' he sprayed 'molycoat' (graphite like lubrication) and benzine (view the plastic bottle) between the rotor and the bakelite plate.

Afterwards, he managed by using a hot blower to let vapour the benzine and thereafter compared the current consumption of the motor, where the current increased a little bit. Which might be an indication that the concerned bearing being lubricated.



Maybe the hampering dilemma is better visible this time



I hope you understand in which way the coupling clutch is functioning

According Hans, it is rather astonishing that after >75 years have been passed, that the lubrication found inside the bearing wasn't 'sticky' or solid.



Re-assemblage, demands some care, but isn't a real problem



The mechanical driving power enters via the slit on top of the vertical shaft


YouTube films

Film 00063:    Recording date was: 7 January 2021. Operating voltage 24 V at 1.3 A. The AC loading resistor lays on the right-hand side. Viewing on the CRT screen the output voltage 16 volt ac at 135 Hz. Down on the right-hand side the dual-key coding module.


Film 00064:    Viewing briefly the mounting place of the rotary converter of the FuG 25a transponder.


To be continued in due course





By Arthur O. Bauer