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saba: Stereo 11; 300 Automatic

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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » saba: Stereo 11; 300 Automatic
           
John Kershaw
 
 
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19.Apr.09 20:48

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Greetings from Canada,

    My Saba 300 has a problem with the automatic tuning. It works normally in search and fast mode in both directions, except it won't stop in one direction  when it tunes in a station on MW/Broadcast band. FM works normally in both directions. I have cleaned and checked the control switches and they appear good. All capacitors are new. A new ECL80 and EABC80 does not cure this. The AM output from the control transformer appears the same in either direction. I have checked the alignment of the transformer. The translation by Google from German is awful and I can't understand much of it.

    Has anyone had this problem and can help?

               Regards, Gary

        

Kirk Sievers
 
 
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21.Apr.09 18:32

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Hi Gary,

Since the FM search tune is working fine, one would suspect a problem with the MW Control Transformer alignment. My experience has been that the IF strip alignment and control transformer alignment interract and the best results are obtained by exciting the ECH81 grid (pin 2) with a RF sweep generator set to 460KHZ with a 20-30 KHZ sweep and then looking at the IF curve (top of R23) and control transformer curve (Point P) using a scope. Get the two curves lined up together and make sure the frequency discriminator output (Point M) is symmetrical around the peaks of the IF and Control Transformer curves.

You may also want to double check (using an ohm meter) all the search tune switch contacts.

Also, verify that the 60HZ drive signal amplitude on Pin 9 of the ECL80  is the same in up and down search for both fast and slow tuning.

Also, verify the value of the 18K braking resistor, R103.

Also, verify that the coupling adjustment (taped over hole on Control Transformer) has not been tampered with.

Hope this helps. Thes radios can be a little finicky to tune up precisely.

Regards,

 

Kirk

  
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