telefunken: 876WK (T876WK); Gross-Super - schematic differences

Gentlemen,

Like Mr Carabas,

I am also beginning the alignment procedures on the early 1937/1938 Telefunken receivers; however, I am somewhat still curious to explain some minor circuit changes (or improvements).

In my model T776WK, the mixer-oscillator tube ACH1 does not reflect the addition of the small 250pF capacitor which bridges the kathode and the filament pins???

Then in the output stage, from the audio pre-amp in the AM2 tuning eye to the control grid, there is the identical coupling capacitor and the 0.5M ohm resistor phowever, the 776WK places a final 100 ohm resistor entering the grid. . . . . . .while in the 876WK the circuitry the corresponding resistor is rated for 1K ohms.

Are these 2 small parts significant enough to render the receiver "muted" if not precisely followed?

One last question - although I have had the radio for some time, I was not able to locate dropping resistor R43. If the previous owner (or technician) removed the item and did not replace it; could the item have been mounts somewhere on the loudspeaker assembly??

Respectfully,

Robert

I would also like to express my sincere Appreciation and Thanks to member Mr Hugo Sneyers for the replacement of the complete BF2 cylinder - without which the Telefunken Gross-Super could not be "restored". . . . . . . . . . 

NOTE: I have prepared what I believe to be a complete "TFK 776WK Alignments" procedural checklist (in English) if one of the radio engineers would be kind enough to review my efforts. I have not yet "folded in" the Illustrations, but I have included a brief description of the needed graphics. I have also included the use of my recently acquired Rohde & Schwarz BN4114 Signal Generator as one of the principal test equipment items.  

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Hi Robert.

 1)In Model Tfk 876WK the 250pF bridges the filament to ground, Katode is grounded directly

 2) the two smal Parts 100 ohm/ 1 k should prevent the AL4 from VHF generating. The value isn,t so important. Usualy it is 50 Ohm to 1k.

3) Resistors R43/44/45 divide the Ug2 for the ACH1/ AF3 aprox. 80 Volts. R45 in the same way reduces the voltage by aprox. 5 Volts.They are adjustable at the Chassis backside, for strong Stations. You find all these Items on the innerchassis.

4) I would like review your english Aligment, please send them by email. Regards J. Leber

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Hello Johann,

Thank you so much for the information - the main reason I was asking is because the original illustrations depicted the R43 dropping resistor connecting from AF3 pin7 over to the AL4 pin 7 and it seemed to be "out  of place". I realize that frequently some tube pins are used strictly for connecting points. . . . . . . .

I have also prepared the accompanying "setup" procedures which were produced by Telefunken to assist in the correct alignment steps for these peculiar radios. 

I will send both files (via email) for your review  - and also add the comment that some other German members have had some "challenges" as recently as January 2010 while attempting to align the specific TFK 776WK - because of the peculiar front end.

Respectfully,

Robert

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