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Of these old Sogema Casssis I had about 50 copies under the soldering iron and therefore also made important recordings, maybe someone needs something like this? 

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  SOGEMA AS-JB70 21-28 

  The factory set 148Volt DC (measured by inductor L2) are slightly inflated and unnecessary burn rather useless components. 25 and 28 "picture tubes are supplied with sufficient 140Volt power supply but not the vertical output stage will see 25 volts (measuring point L3)! To allow for some devices an economic adjustment, the resistor R31 must be changed from 3.9 to 4.3 K, then the adjustment should be approximately between 128-150 volts! 

  At 140 volts at L2 the vertical stress is about 25 volts at L3, the line output transformer (ELDOR Typ28024730) or alternative HR flyback transformer (HR 7027 1BP1) is pretty hot! The power supply is built convincing, also has filter chokes before the Ladeelkos, and is adequately protected! It regulates in bad electrolytic capacitors (unlike comparatively HANTAREX POLO), the output voltages back and therefore not break anything, in very low capacity, it may take a long time until it finally starts to oscillate! 

  The PAL / NTSC decoder TDA3562A operates as before about 25 years in television sets, (even if only used as a video amplifier). The setting of the G2 voltage at the line transformer requires tact, as reference voltages are fed back to the Videoverstäker! The feedback signals as a sum of product was recovered from the collector current of the video output stages via the voltage divider R424 and R427 and to pin 18 for TDA3562A recycled, this circuit also Zeilenrücklaufaustastung is performed. For the picture tube adjustment to adjust the G2 controller with test image to the right until the carriage return is visible, then turn back slowly and carefully again until the picture is displayed correctly. If no image appears may be defective and the TDA3562! The brightness correction must not be carried with G2 controller! 

  R-G-B balance: 

  This unit no conventional gray balance can be performed only with test pattern can the adjustment controls P401 and P402 on the CRT board the RGB balance can be adjusted! For the contrast control applies the wisdom of "less is more"! 



  ! Common Mistakes! 

  Bright picture with retrace line: Probably the protective resistor is R401 (10R) on the CRT board high-impedance. 

  Bad electrolytic capacitors in the power supply: 

  C19 100uF 63V Capacity Loser (PSU builds very slowly operating voltage, can last up to an hour)! A bad C20 47uF 25V generated at the power supply output 50Hz interference, C16 loses some capacity, an open C11 means with 50 Hz superimposed whistle from the flyback converter transformer! These capacitors are very close to the power resistors and are indirectly heated! 

  Loser capacity electrolytic capacitor C 25 causes severe vertical error: 



  Insidious error: 

  In high-impedance resistors R411, R414 or R417 (68K 1W) on the CRT board and the video amplifier TDA3562A sends it inspected no usable video signals, these resistors and the video output stages. 

  The exotic TDA4800 to pin 12 has a 100K control (from P4), thus limiting the range of possible upper image overlap can be adjusted. If this resistance is high impedance, the oscillator oscillates randomly in the range between 90 to 250 Hz on the screen is then centered only about 10 cm high gray image to see with carriage return. Since in this case the TDA3562A to pin 7 no standardized Sand Caste sees pulses also no useful video information are reported to the police! When soldering defects on the image width the image width coil transistor goes into saturation, consequently, the horizontal output stage is killed, you can hear this error on the strong whistling switching power supply and the protective resistor R136 soldered out due to thermal overload by itself. The exotic Horizontal S2000AF transistor can be replaced by a fast 2SC5148. 
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  PS: Do not allow any gray hairs grow, everything can be repaired. Always just a matter of time!