Restoration of an tube controlled saturation transformer

[Martin.M]

hello friends,

this old Philips is a Stabilizer for the AC Line, still glowing.
A ultra heavy equipment, 2 persons have a problem to handle it 

Philips 7776/06 made in Belgium, in the late 50`s.

Technical datas.

Input Voltage: any from 187 to 242V ~
maximum load: continuous 10A, 30min. 15A
Output Voltage: 220V +/- 0,1%  (adjustable).

How it works.

There is a very special diode tube inside what control it`s resistance by the own heating filament. This is connected to a Transformer what is parallel to the output. The resistance of this tube will drive another Tube what control a big and heavy saturation transformer. In front of this is a large Transformer, its secondary winding of 60v is in series with the AC Line, going to the saturation transformer.
So the voltage there will be (input voltage +60v) bevor it`s going to regulation. So the apparat can work with input voltage much lower then the output voltage. The other tubes inside are periphery, 2 rectifiers and a driver for the EL34. All in all there are 5 tubes glowing.

See a lot of pictures from the restoration on my website, at http://www.wellenkino.de/forum/thema.php?board=2&thema=30

greetings
Martin

[N2IXK]

Cool!  Love that old "brute force" technology!

How hard is the 56001 emission limited diode tube to find nowadays? Never heard of that type here. Similar saturable reactor systems here in the states usually used either a 2AS15 or a 5947.  Both of which are getting a bit hard to find nowadays.

[Martin.M]

thank you 

56001 is very rare. I found it on ebay, 2 pcs. nos in box, in spain. So the old Philips will have a very long life.

This 2AS15 tube, I know it also.
There is one in every Tek 555, "triple nickel", this large old scope regulate the complete filamenting also by a saturation transformer.
Here are 2 of that scopes at home 

greetings
Martin

[N2IXK]

Does the 56001 incorporate the same "safety bypass" as the 2AS15? On that tube, there is an internal switch that will short plate to filament if the filament opens, causing the regulator output to go to minimum rather than maximum when the tube fails.

Any chance you can post a schematic of this beast?

[Martin.M]

Sorry I have no shematic of that. The books will arrive later to me, the pre owner is searching for them.

Yes it have this bypass also.
The differents to the american tube ist only the filamenting voltage and it have a rimlock socket.

greetings
Martin

[PA0PBZ]

Interesting, it looks like the filament is held up by a spring that shorts to a little hook connected to the anode when the filament breaks.

[N2IXK]

Looks very similar to the arrangement in the 2AS15. If the filament breaks, the tension spring is released, and snaps into contact with a plate support rod, shorting the tube. There is also a pair of shorted pins in the base, intended to be used to prevent the application of power without the tube in the socket.

The Bendix 5947 didn't have this feature (at least the samples I have seen), which was unusual considering that it was aimed at high-reliability aircraft and military gear. 

I believe all these tubes use pure tungsten filaments, rather than oxide coated or thoriated emitters.  Pure tungsten works well over a wide temperature range. These tubes are generally operated in "emission limited" mode, where the plate current is more or less independent of plate voltage, but varies proportional to filament temperature.