kriegsfunker

Luftwaffe NA8 utility power supply for 100 Watt Sender

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kriegsfunker

After a year of waiting, I got this power supply.  It weighs around 90 KG and broke my hydraulic hand-truck moving it to the shelf.   It looks complete inside, so I will restore it  (slowly).

 

 

 

Screenshot from 2018-12-29 16-37-58.jpg

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kriegsfunker

Closeup of the data plate

Screenshot from 2019-01-01 13-11-22.jpg

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val
Moderator

Thank you Yuri, very nice! I'd love to see the inside of it.

Here is for comparison another NA8, front panel seems little bit different,

quite possibly doctored...

https://picclick.de/Gehäuse-Sender-Netzteil-NA8-der-Wehrmacht-ideal-für-Selbstbau-Röhrenverstärker-263844641328.html

 

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kriegsfunker

Yeah, definitely doctored, and stripped.   Here's my interior.  It's definitely restorable, which I've started doing now.

 

 

Screenshot from 2019-01-01 13-19-00.jpg

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kriegsfunker

Most of the weight is in the transformers.   Behind the selenium rectifier array, there's a double winding massive transformer which probably weights 1/2 of the device.  There are 4 other transformers in there as well.

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Funksammler
Moderator

Nice one! I like that you can adjust the output power of the transmitter by setting the anode voltage. The vehicle power supply does not have this facility, it just generates 1000V. The NA6 was often used with the 100 W.S. and a Morseschreiber as a Luftwaffe beacon station. The luftwaffe multi engined aircraft could use their PeilG6 radio direction finders to navigate using these beacons.

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kriegsfunker

Thanks FS.  The AC input voltage can be changed by connecting to the appropriate terminal on the input transformer.

Screen Shot 2019-01-02 at 9.01.11 AM.JPG

This will also allow me to finally build a tube tester for the RS-237.

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kriegsfunker

A few years ago, I was offered one of these.   The insides are a bit different.  Notably, the selenium rectifiers are different.

DSCN0690.JPG

DSCN0691.JPG

DSCN0697.JPG

DSCN0699.JPG

Edited by kriegsfunker

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val
Moderator

Yuri - one special request please - when you start restoring it, show what type of Glimmlampe there is.

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Desert Rat

Hello to all you technical experts,

I just wondered where on earth do you find these superb radio sets etc....I would have thought most would have been destroyed after WW2 but it seem there are many more to be found...Good Luck!

Thanks for showing us on MCN these rare and great memorable items.

Desert Rat

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kriegsfunker
2 hours ago, val said:

Yuri - one special request please - when you start restoring it, show what type of Glimmlampe there is.

Of course!

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kriegsfunker
6 hours ago, val said:

Yuri - one special request please - when you start restoring it, show what type of Glimmlampe there is.

Do you have one of these?

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kriegsfunker

Here's a photo from a field manual showing the NA8 installed in some vehicle. Note the different locations of the power terminals:

 

 

Screenshot from 2019-01-03 22-22-32.jpg

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val
Moderator
On 03/01/2019 at 04:17, kriegsfunker said:

Do you have one of these?

No, my friend has one.

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kriegsfunker

Restoring the main transformer.   

 

 

Screen Shot 2019-01-04 at 9.14.56 AM.JPG

Screen Shot 2019-01-04 at 9.15.58 AM.JPG

Screen Shot 2019-01-04 at 9.16.21 AM.JPG

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kriegsfunker

Testing the high voltage rectifier.  It works.

Screen Shot 2019-01-04 at 9.18.41 AM.JPG

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kriegsfunker
18 hours ago, val said:

No, my friend has one.

Here is the lamp

 

 

Screenshot from 2019-01-04 21-45-26.jpg

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kriegsfunker

Val - please ask your friend to measure the resistor on top of the huge capacitor under the transmitter power output terminals.  My resistor is dead.

 

Screenshot from 2019-01-04 22-01-21.jpg

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val
Moderator
8 hours ago, kriegsfunker said:

Here is the lamp

Thanks! Any visible markings there?

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val
Moderator
On 05/01/2019 at 08:03, kriegsfunker said:

Val - please ask your friend to measure the resistor on top of the huge capacitor under the transmitter power output terminals.  My resistor is dead.

Asked - sorry, his set missed that resistor alltogether :(

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kriegsfunker

What resistor value would you use for a "bleed-off" resistor on a 32 uF 1.2 kV capacitor made for 1000 Volts DC at 250 mA?

Edited by kriegsfunker
Correction

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val
Moderator
59 minutes ago, kriegsfunker said:

What resistor value would you use for a "bleed-off" resistor on a 32 uF 1.2 kW capacitor made for 1000 Volts DC at 250 mA?

If i have to guess i'd use something around 10MΩ as a permanent bleeder.

This would give a slow discharge something between 5...10 min.

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kriegsfunker

Based on the following calculations, I'm buying this resistor:

 

Screen Shot 2019-01-07 at 4.24.10 PM.JPG

Screen Shot 2019-01-07 at 4.24.23 PM.JPG

Screen Shot 2019-01-07 at 4.24.34 PM.JPG

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Funksammler
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You probably want to give the resistor clamps a good clean, I find it hard to believe that the resistor wire (embedded in glaze) is defective. It looks like the clamps just connect to the wire by pressure...

regards,

Funksammler

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