Meersburg Automatic 125

      Hi!

      I've been admiring those nice tube radios for quite some time. Last month I got lucky on the flea market and found a Meersburg 125 in not-so-bad condition. It's the first one I've ever seen or listened to and it's really great, although not everything's working the way it should.
      I don't know much about electronics, even old fashioned one ;) I can handle a voltmeter and a soldering iron, but apart from that... I did some research on the internet, found the schematics and now I found this very nice forum.


      Well my Meersburg is missing a few bits but it works. First I did some mechanical work (fixed a broken dial cord, fixed the stuck clutch), then I've replaced almost all paper capacitors and some electrolytics also. The 0.022 uF capacitor near the Graetz diode bridge has melted during the first hour of playing (it's been replaced now), does that happen because of the bad capacitor or the diode bridge or something else ?
      Also, the automatic seeking doesn't work. When I turn it on I can feel the vibrations from the motor and the knob very slowly turns in the direction of a strong station, but it doesn't have enough power or speed to move any further. I haven't replaced the big 0.3uF paper capacitor yet. Could that be the culprit for the weak automatic motor ?

      There is another problem, a constant hum in the speakers, noticable when the volume is low. Even if I press the automatic-seek buttons, which turn the sound off, the hum is there. Is that normal ?

      Thank you for your help,
      Rok from Slovenia

      Hi, thanks for your answers.

      I'll replace the motor capacitor as soon as I can get them. I'll try to get some spare tubes and test them as well.

      deltamike55, what do you mean by smoothing capacitors, do you mean that big double ElKo in a can(50uF)? I've already replaced it. There's only two paper capacitors in the power supply left, small (a few nF) 1000V. I'll have to order them as the small town's electronics shop I go to doesn't stock high voltage capacitors...

      And, regarding the hum, one of the transformers is also humming. I've been told that transformers hum in general, but do they hum on a Saba ? It's audible only if you are very close to the radio.

      I hope those questions are not too stupid, but as I've said before, I'm not good with electrics/electronics.I'd love to have a nice, working Saba though.

      thanks,
      Rok

      Hi.

      On Friday I finally got the ordered capacitors so I could continue. I've replaced the big paper motor capacitor and now the automatic tuning works ! The way it moves and stops at a strong station is quite magical :)

      But still, there are other problems with the radio:
      - the hum is still there ( couldn't try swapping tubes as I don't have any spares apart from one EABC80 yet)
      - when i turn it on the reception on UKW is really good and the band on the magic eye is thin as it's supposed to be. After a while the band widens and the reception noticeably decreases. If i switch to K,M,L or turn the Automatic on for a while and then go back to UKW the reception becomes good again ( for a while, then it deteriorates again).

      If you have any suggestions I'd be very grafetul.

      bye,Rok

      I was just joking a bit :)

      Well yesterday I took some more time to look at the radio and compare it to the schematics. There is a 700 pf capacitor soldered between the base of EF85 and one of the filters. I can't find it on the schematics ( or I can't read it properly). Unlike all the other capacitors (ERO or SABA) this is Iskra, a slovenian company, so somebody has tried to fix something in the past. Also a resistor next to it looks non-original.



      Could this capacitor or EF85 be the cause of my radio's problems ( reception getting weak after a while) ?

      thanks,
      Rok

      Hello,

      an update:

      today I've replaced that green capacitor (so there's no more paper capacitors in the Meersburg) with a new 4700 pF ( according to the scheme that's what should be there) and now the reception stays good !!! :) :) :)

      But, of course, another problem surfaced or appeared ...

      After a while (2-3 minutes) of really great sound with strong bass something starts to go wrong, the bass becomes weak ( if I turn the bass-pot towards max. level the bass becomes weak and crack-like). I have noticed one of the amplifier tubes EL86 turns really hot, so hot I can barely touch it without burning myself while the other is cooler. I've swapped them and again, the same tube is hot ( so the temperature is not connected to which socket the tube's in).
      As I've said before, I am a newbie in the world of tube radios... how hot do tubes get ? I didn't play the radio very loud, just normal room listening.

      thank you for your answers,Rok

      Hi Rok,
      if the distortions of lower frequencies have their origin in the output stage you should first replace any electrolytic cathode capacitors of the power pentodes ECL 86.
      One of the tubes themselves can be the culprit as well. It´s no bad idea to replace them anyway. If you want to know which one is in charge you´ll have to do some measuring of the DC Voltages of both tubes first.
      Achim

      Hi,

      today I did some measuring:

      Tube 5:
      pin 6: 276 V [ should be 255V]
      pin 7: 6.6 V [7V]
      pin 9: 168 V [170V]

      Tube 6: ( the "hot" one)
      pin 6: 199 V [255V]
      pin 7: 22.6 V !!! [7V]
      pin 9: 116 V [100 V]

      When I swapped the tubes (and started measuring immediately after I've turned the radio on) the tube in socket 5 ( the hot one ) started to heat up and the voltage at the pin 7 started to rise and when it reached cca 15 V I turned the radio off).

      I'm confused. Something's got to be wrong with that tube, but how can the heater voltage rise just like that ?


      thanks,
      Rok