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telefunken: 6; Opus

Martin Renz Ernst Erb Vincent de Franco Martin Bösch Mark Hippenstiel Bernhard Nagel Dietmar Rudolph Otmar Jung Heribert Jung Eilert Menke 
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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » telefunken: 6; Opus
Omer Suleimanagich
Omer Suleimanagich
USA  Articles: 428
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05.May.05 06:16

Count of Thanks: 7
Reply  |  You aren't logged in. (Guest)   1 I have recently resurrected an Opus 6 from the dead!

Amongst things that were done to the radio including recapping, replacement of off tolerance resistors, Ferrite antenna repair, re stringing FM, lubricating all moving parts, replacement of very weak tubes/valves, spot speaker repair on one of the speakers, the cabinet needed the base to be reattached, veneer repair, and refinishing.

Not that I'm bragging, but this is the type of stuff we are all here for!

After getting the radio to work, and adjusting the FM tuning to the scale, I wish to improve the sensitivity on MW/AM.

All connecting wires on the ferrite core antenna are connected properly and there are no shorts. All the resistors around the ECH81 are within tolerance. ECH 81 is new (Telefunken!). Radio is receiving maybe 65-75% of its potential.

How does one go about increasing the sensitivity in this radio?


P. S. This table radio, with its six speakers, is in my opinion, a Stradivarius in fiftie's German radios!
Hans M. Knoll
Hans M. Knoll
D  Articles: 2128
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05.May.05 10:58

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Reply  |  You aren't logged in. (Guest)   2   Hello Mr. Suleimanagich,

You are searching for some one with experience in improving the receiving ability of this set.    Maybe some one posting here his results.

I to not have this radio, I only can say to you, in this early time 1955/56,  the ferrit -antennas have mostly  40 to 60% from sensitivity of designs from now.
In this time, the sensitivity of the extern Antennas has priority! 

I do not now,, if you mean your set has an failure, or you want to redesign the circuit. From where is your indention of:  Radio is receiving maybe 65-75% of its potential.
Have you make any measurements about sensitivity an grid 1 ( pin2) ECH81 on IF and RF?
The ratio sensitivity on IF to RF on 1Mcs should be: 1 to 1,2 to 1,3 ( for example: 10 uV on IF  to 12 uV on 1Mcs) This is very important for the ratio of signal to noise!
Additional,  from antenna to this G1 ECH81 the RF is the only value to improve  the reception.

The IF gain makes only more noise and wanted power on the speakers. The volume potentiometer can compensate this over a with range! 

Have you test the value of local-oscillator ( Volts AC or Volts DC) on g1 of Triode ECH81?
To you have a Signalgenerator?

O.K. I am waiting for your comments,
Regards Hans M. Knoll

This article was edited 05.May.05 11:10 by Hans M. Knoll .

Omer Suleimanagich
Omer Suleimanagich
USA  Articles: 428
Schem.: 3
Pict.: 56
06.May.05 00:51

Count of Thanks: 6
Reply  |  You aren't logged in. (Guest)   3 Thank you so kindly Herr Knoll for your quick response!

As explained in the first part of this thread, the ferrite antenna was basically in two pieces and had to be reconstructed ( using a metallic epoxy to put the ferrite pieces together), including the thin copper wires needing to be soldered to new 32(?) gauge wire. There was a short in one of the solder its fixed!

As I'm writing this reply, I'm listening to a fifties Hit Parade station, currently playing Cab Calloway's, "Minnie the Moocher", with the magic eye so bright it's blinding me! A station I could barely pickup yesterday

All the very best!