NA8 Restoration
Page 1


The NA8 is the utility power supply for the 100 Watt Transmitter (100W.S. / L.S.100/108).   It was used in airports and other stationary positions where utility power was more practical to use than an Umformer or gasoline generator. 

This specific NA8 was manufactured in March of 1944 judging by the date stamps on some of the components.   It was manufactured for use by the Luftwaffe based on the contract number on the manufacturer label.

The device weighs around 70 KG due to the five transformers and chokes inside.   Although two people could move it with difficulty, it is not recommended for one person to lift it.

This NA8 was complete inside, although some rust, debris and dirt covered most surfaces.  It is definitely worth it to restore to working condition, since it would be expensive to build an equivalent power supply with modern components which delivers 1000V and 12V with the correct current.




Next we have the LV transformer.



LV transformer on the bench being cleaned.



Input voltages range from 110 to 220, just like on the HV transformer.   It will be set to 125VAC just like the HV transformer.



Top - the LV selenium rectifier, and the LV filter choke is below.



All restorable parts are out, and the chassis is empty.  This is when I pick it up and move it.



Another photo of the empty chassis.



The LV selenium rectifier will be replaced by a modern 1000V full-wave silicon rectifier bridge.  It is mounted on a metal bracket attached to the LV filter choke.



All of the major internal components on the shelf.



A new 3000V full-wave silicon rectifier bridge is installed inside the original HV selenium rectifier.



Original wiring is used and is connected to the terminal block on top of the old selenium rectifier.



This is the loading resistor for the voltmeter.  You cannot operate the HV fucntion of the voltmeter without this resistor, or the voltmeter will be destroyed.



Here, the new silicon rectifier is mounted on the LV choke.



The LV transformer is installed back into the chassis.



LV filter capacitors installed back into the chassis.



 A new bleed-off resistor is installed together with the old resistor.



 New resistor as viewed from the top.



Finally the HV transformer and rectifier are installed.



The reassembled NA8



The reassembled NA8



AThe reassembled NA8



The reassembled NA8



The reassembled NA8



Rear of the voltmeter.



Voltmeter removed.



Testing the voltmeter function