stern-sonn: 697/75GWU 3D; Sekretär III
ID: 166046
This article refers to the model: Sekretär III 697/75GWU 3D (Stern-Radio Sonneberg, VEB, RFT; SONRA; -vorm.: EAK (Ostd.) - ex. AEG)
stern-sonn: 697/75GWU 3D; Sekretär III
16.Jun.08 23:19
0
I'm restoring a Sekretär III 697/75GWU 3D radio. There wasn't a schematic for this model in RMorg but I used a schematic for model Sekretär III 697/62GWU which I believe to be close enough. There are no component values in the schematic and I need to know the value of one resistor. It is burned open and the markings are no longer visible. I think it is R11 in the schematic (in the lower left corner, antenna circuit). I have no idea how it got burned. There is no visible damage in the other components.
Also I removed the 50 + 100 uF electrolytic capacitor can but I forgot to look which one is the first and which one is the second filter. I'm guessing that the 100 uF is the first. Am I right?
The final question is about the half wave selenium rectifier. I measured its resistance with a digital ohm meter and I got 1.3 megaohms in the other direction and 1.6 megaohms in the other. I assume that it is bad?
All answers will be greatly appreciated.
Timo
Also I removed the 50 + 100 uF electrolytic capacitor can but I forgot to look which one is the first and which one is the second filter. I'm guessing that the 100 uF is the first. Am I right?
The final question is about the half wave selenium rectifier. I measured its resistance with a digital ohm meter and I got 1.3 megaohms in the other direction and 1.6 megaohms in the other. I assume that it is bad?
All answers will be greatly appreciated.
Timo
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17.Jun.08 15:56
Hello Timo,
you can use the schematic of the 697/77 GWU Sekretär 4 modell. The component values are added there.
You can't check a selenium rectifier with a digital ohm meter. Check the anode voltages instead. If they all are too low, or the rectifier gets hot, this indicates a possibly bad rectifier.
For more information look here and may be here and here (about restauration in general by Hans Knoll)
you can use the schematic of the 697/77 GWU Sekretär 4 modell. The component values are added there.
You can't check a selenium rectifier with a digital ohm meter. Check the anode voltages instead. If they all are too low, or the rectifier gets hot, this indicates a possibly bad rectifier.
For more information look here and may be here and here (about restauration in general by Hans Knoll)
To thank the Author because you find the post helpful or well done.
17.Jun.08 20:46
Thank you Martin. I have checked selenium bridge rectifiers before with a digital meter and they behaved just like normal diodes. None of them showed reverse leakage but this one does. I'll try carefully how the original rectifier performs. I already tried the radio with a silicon diode + resistor and it worked but quite weakly. It seems that the volume potentiometer has some problems. And it needs a new UM80 eye tube. Maybe some other tube is also bad.
Timo
Timo
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