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Alignment of SABA Automatics

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Documenti » Radio: riparazione del circuito (interno) » Alignment of SABA Automatics
           
Konrad Birkner † 12.08.2014
Konrad Birkner † 12.08.2014
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18.Jul.12 11:31
 
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There was apparently a special alignment workstation at the SABA factory where the AFC IF transformer alignment occurred. After  alignment the filters were sealed.

Probably it was believed that a thorough re-adjustment wasn't possible in an ordinary service workshop. In all service instructions for the automatic models only a slight retuning of the resonant circuits is mentioned. It is expressly warned not to touch the coupling adjustment (which is fixed by construction on most other IF Transformers).

Unfortunately it is regularly found that somebody inexperienced had tampered with the coupling adjustment.

In other Service instructions it is even recommended to set the coupling screw to its end stop. But there is not the faintest hint how to reset it. The radio would not work to specification of course. It must be an editorial error that the explanation was missing. 

It was not until the era of automatic motor tuning was ending that SABA published a general paper "Alignment Procedure for SABA Radio Receivers" describing how to adjust the coupling (last page).

Most IFTs only the frequency can be adjusted. The spacing between the pair of coils affects the bandwidth and the shape of response, unusually this is adjustable on the SABA IFT. If the spacing is too far, at outer end-stops, the response is too broad. If the coupling is completely tight the response widens again with a nasty dip in the middle.  For VHF-FM IF "critical" coupling is likely too narrow, especially for stereo (the spacing that gives sharpest peak with no hint of dip).

 

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Questo articolo è stato modificato il 19.Jul.12 08:35 da Konrad Birkner † 12.08.2014 .

Mike Izycky
Mike Izycky
 
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19.Jul.12 01:07

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I must take the time to thank Konrad for posting this article. Many, many years ago when we met in person he told me that this was not a procedure to undertake lightly; but as the owner of several SABA-Automatics, inevitably one will be found where this needs to be done. Now I can perform these adjustments with confidence.

Konrad - thank you!

Regards,

Mike.

  
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