grundig 5040w3d circuitry analysis

Posted on Feb 5, 2014

On the primary winding of the first IF transformer there is no capacitor. Does that mean it has only one tuned circuit, and the primary coil is just an inductive coupling The routing of the twisted pair couldn`t be done exactly the same every time. Was it necessary after assembly of the complete set to readjust the coil in the tuner (at the anode of the second section of the ECC85),

grundig 5040w3d circuitry analysis
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or was it sufficient to simply adjust the first IF transformer I`m looking forward to lively participation. Whoever doesn`t have access topost in this forum is welcome to send me (Thomas G. or Tom A. )questions by email. [To send an email to me (Tom A. ), click on "mail to the author" at the bottom of this thread. To send an email to Thomas G. , go the the German_thread and click on "mail to the author" at the bottom of the first post. ] The twisted pair transmission line between the FM tuner and the first IF stage is twisted so that it can serve as a balanced (symmetric) transmission line with nearly constant impedance. The characteristic impedance is determined by the diameter of both wires and their distance from one another (in this case, the thickness of the insulation times two). The first IF transformer, which has only one adjustable ferrite core, I would assume has its primary and secondary winding tightly coupled, so thatthe primary capacitance is transformed to the secondary. The primary winding is necessary in order to couple the balanced feed line (the twisted pair) to the unbalanced grid circuit of the first IF stage. Therefore a transformer with a single tuned circuit and a coupling coil is used. Given that the FM tuner was previously aligned, no additional readjustment of the output circuit of the ECC85 in the tuner is necessary after final assembly. For the previous alignment of the tuner, it would be...

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