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centrum: FU46 (FU 46);

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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » centrum: FU46 (FU 46);
           
Luis Borges
 
 
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11.Aug.09 20:49

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Hello, i have a Centrum FU 46 in my colection, and i recently decide to put some restauratin in progress . When i look at the chassis i notice that it was differnt from the one that is on the Radiomuseum web site. This is a AC/DC device , has 2 rectifier valves (25Z5) This is very strange to me!

This radio has also an EBF2; 6D6; 6A7, and a 25L6GT valves, total of 6 valves.

The audio output valve is 25L6GT but this is not the original, someone has put this on the radio and conected to a baseplate adapter.

Can anyone tell me witch is the original audio output valve for this radio??

Some aditional information about this radio will be very helpful.

Best regards to all

 

Luis Borges

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Torbjörn Forsman
 
 
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12.Aug.09 22:15

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If the socket for the output valve is an american 6-pin socket, the output valve could originally have been a 43 or a 25B5. Check whether the cathode resistor and decoupling capacitor for the output valve seems to have been installed afterwards (or maybe within the adapter), then the original valve was probably a 25B5 which does not need a cathode resistor.

As the AC model of FU46 has a 42 output valve, it would be good chances that the AC/DC model should use a 43.

A reason for using two 25Z5 can be to halve the load on each valve which means longer life for the valves and lower voltage drop. It is fairly common to find grossly oversized rectifier valves in swedish radios from the mid-30's.

Anders Söderström
 
 
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13.Aug.09 22:05

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Hello

The posted Centrum model seem to have the wrong chassis. All Centrum radios with an "U" in the typecode are AC/DC powered recievers. The chassis in the posted model is likely to be from a model FW 45. There may of course be some odd and special exceptions from the rule, but i have never heard of any, so that is my theory.

However, swedish radiomanufacturer Tjerneld sometimes used the same chassis as Centrum. (There must have been some cooperation between the companies, but the details are unknown) The models Tjerneld 66 A and 77 A seem to use the chassis of FU 46. I own a model 77 A in bad condition and it is present here at RMorg.

http://www.radiomuseum.org/r/tjemeld_77a77.html

As you can se at the model page i havent been able to list two of the tubes. One of them is a 25Z6 with converted socket and the other one might be a 12Z3, but its difficult to read for sure. I can of course not guarantee that the tubes listed are the original ones, but if they are, it seems that the output tube should be 12A5 and that there should be a 6B7 instead of that EBF2 on your chassis.

To be sure that at least your chassis is the same as in my Tjerneld: Check the numbers stamped on the backside of the chassis. (Usually in the Pertinax of the aerial and gramophone connectors). It should read 16 - xxxx, where the four x:s is the productionnumber, and it will correspond to the number stamped on the backplate of the radio. (Chassisnumber is 16, while the chassis number for a FW 45 or Tjerneld 66 V and 77 V would be 15)

I hope this will be of some help.

Greetings from Anders "soda" Söderström, Sweden 

  
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