SABA Freiburg 14

      O.K. then, you schuld first attach yout scope to the connection R714/R716. Triggering should be set to "TV" or mains frequency.

      Then, during FM-tuning watch the output of the automatic-discriminator as shown here in Post 525:

      http://saba.magnetofon.de/showtopic.php?threadid=3664&pagenum=22

      Please observe the signal, when you are on a station and when carefully leaving the station downwards and upwards. Maybe you can make some screenshots of the scope's display so we can see the signal's shape and amplitude.
      Achim

      Last night I changed R105 for 60Hz operation (I missed that change but I changed all the other caps and resistors) and re-peaked the IF xfmr. It help the receive signal and quality but not solve the low P-Y voltage. I compared the FM primary DC resistance of IF-V to others and found it should be good. (I also measured the AM primary wrong. It measured 5.6 ohms).

      With the oscilloscope attached to M (junction of R716, C714), I managed to adjust the “Do Not Adjust” slug K782/5 until the scope looked “good”. That is when I moved the tuning knob off center the 60 Hz signal had good amplitude and the motor had strong correcting torque (error signal). Adjusting it too far shows high amplitude but decreasing motor torque. Therefore, “Good” means it just felt correct and looked correct.

      Off channel when I turn the tuning knob:


      Off channel when I turn the knob the other way:




      On channel:






      The AVC signal between P-Y are still low. I injected 10.7 MHz to the grid of Ro701-2 and could easily achieve 22 volts P-Y. So it must be a lack of signal up stream. But the tuning indicator closes just about all the way (1-2mm gap).

      Today I will look “UP-Stream” for bad components as was suggested before.

      I will upload pictures to this forum but if that fails please look at my hobby web page for oscilloscope images of this radio. http://www.ppinyot.com/saba/fr14.htm



      Thanks to all for the input! I really appreciate the help and want to contribute as well.

      Paul P.

      P.S. I attempted to include images but failed. How do I accopmlish inclusion of images? Sorry for being a "pain in the ....."

      After replacing the resistor in the FM tuner the automatic tuning works much better. I must go back and re-align the FM section to see if the P-Y voltage will make it to 22 volts. But the motor drive is much stronger.

      I may have had a cold solder joint at the junction of C703 and C704. I replaced both capacitors and improved the operation. When I put the original caps back in one at a time (to find the bad one, they both tested good on the B&K capacitance meter) the circuit continued to function strongly. Or I created a cold solder joint from the coax to Ro701-2 grid when I replaced an out of tolerance resistor on the first restoration effort.

      Is the coax used as a 14pf capacitor C705?

      The 60 Hz (50 Hz) modulation from the low voltage supply (diode E25 C5, reference connector "C") is not sinusoidal. It is distorted almost like a triangular slope at the top of the curve starting at about 75/80 deg and ending at 90 deg. Then procedes to 180 as a distorted/sloped curve. Will this affect the operation of the seak? I can supply an image if needed (tomorrow).

      The auto tune stops on just about all the FM station when tuning Up the frequency. It skips all stations when going down in frequency. This is a new challenge.

      All in all I am much happier with the progress. But it is not totally correct.

      Any thoughts?

      Paul P.

      P.S. I found the discussion on how to upload pictures but the server does not recognize me as a registered user. I receive errors.

      Hello Paul,

      The signal at "C" needn´t be sinusoidal since it´s being rectified. it´s just a (distorted) half-sinusoidal signal.

      Good to hear there´s some progress with the Automatic-issue!

      Looks like you´re right with the cable being the 14p capacitor by the way.

      The asymmetry in the search behaviour can generally be caused by mechanical problems (dial-cord, lack of lube...) or misalignment of the automatic-control-filter.

      Please note: Measuring the old paper-capacitors can trick you!
      Most instruments show a capacity that´s too high and don`t show the lack of isolation that MANY of these capacitors have. This can be a massive obstacle to the proper function of the tube-circuits.

      It´s best practise to replace them all regardless of what´s being measured.
      Achim

      Nightbear,

      I have replaced many capacitors including electrolytic. I did not replace the clear capacitors (I think they are polystyrene. There is no schematic materials symbol). They have taken on a yellowed color. Should these capacitors be replaced too?

      I manage to align the FM IF sections and control transformer to get 22 volts P-Y as specified. It scans and stops on all stations (of decent signal strength).

      The tuning motor "dances" to the Bass notes on FM. Do you have any suggestions about this Dancing tuner? I did replace the 5 nf discriminator capacitors C712 and 713 (and the resistors). Perhaps are these new capacitors too low in value (4.7 nf)?

      Paul P.

      Hello Paul,

      congrats it seems you´re almost done!

      The "clear" capacitors needn´t (mustn`t) be replaced, they are made of polystyrol (Styroflex) and they never ever fail.

      The tuning motor dances by design - no need to worry about that!
      It happens due to low frequency demodulated Signals. Those low frequent tones cannot be filtered out by the low-pass filters behind the discriminator since this would kill the 50 Hz Modulation (60 Hz in the US) for the tuning control also.

      Don´t change the values of the low-pass filters, let it dance - they all dance :)

      Merry christmas!
      Achim

      Nightbear,

      Thank you for the reply. I am happy to read the tuning motor dances with the modulation.
      http://www.youtube.com/watch?v=bQr_oCmQGuw (A little dance music).

      I will keep the clear capacitors. I suspected they were good. I tested a few on the B&K solid state capacitor tester. I have an "Old School"' cap tester with green eye tube. That baby can put up to ~600volts on the cap and will show leakage. But if I have to go that far then I figure replacment is faster and safer.

      This 14’s alignment is all but done. I have to remount the dial scale, line up the dial indicator and wax the trim screws for shipping. I keep the glass separate since it is so hard to find replacements.

      I purchased a Heathkit FM stereo alignment generator. That helped bring the MUX unit into proper demuxing and operations. I converted the MUX to US de-emphasis according to the schematic.

      Next will be replacement of the burned out 8 volt sub miniature lamps. I do not have an immediate solution for this problem. I am considering grain of wheat lamps with series diodes and/or resistors to match the color and intensity. I may even paint the lamps to match the correct color. I am also considering an LED solution. But that may be quite a challenge. I would change all 8 volt lamps with a new LED solution so the buttons look uniform.

      I want to test the volume motor. I do not have a remote control. I was considering fabricating a compatible remote.

      ??? Do you know of any source of parts for the male connector to the chassis? Do you know where I can buy a compatible remote control?

      Thanks again for all your help. And to everyone else too.

      Paul P.