croustiFajita Posted February 8, 2014 Share Posted February 8, 2014 Hi everyone, is anyone here know the polarity of the zener diode D13 on a Lynx II ? I can't find it anywhere ... Thank you in advance for your replies Ben Quote Link to comment Share on other sites More sharing options...
+Stephen Moss Posted February 10, 2014 Share Posted February 10, 2014 What do you mean by polarity? Diodes have an Anode represented by the arrow part of the schematic symbol and Cathode represented by the bar (Z on Zenner, stylised S on Schottky) part of the schematic symbol. Generally the Anode is the positive connection and the cathode the negative connection, however Zenners conduct in both directions so in their case generally the cathode is connected to the more positive voltage (the one you want to regulate the voltage of) because if you connect the Anode there instead of Zenner regulating it just acts like a standard diode. There should be a coloured bar on one end of the diode case - that always indicates the cathode end of the diode - hope that helps. Quote Link to comment Share on other sites More sharing options...
croustiFajita Posted February 10, 2014 Author Share Posted February 10, 2014 (edited) Thank you for your reply Stephen, I should have been more clear in my previous message, sorry. In fact, I have a faulty Lynx II that i'm trying to repair. I've browsed many forums, and I found that a common failure in the Lynx II is the D13 component, which seems to be (according to the infos I found), a Zener diode (4.3V / 500mW). So I bought some equivalents in order to replace the original one. On the new ones i received, the negative pole is clearly indicated by a blue ring, but i can't guess the negative pole on the original one, neither on the case, or the board. I'm even beginning to wonder if D13 is really a zener .... Here is a picture of the old D13, and one of the new Zerner i received : Thank you for your help PS : Sorry if my questions seems dumb, but if i'm good with a soldering iron, i'm not good in electronics and my knowledge about components is very limited Edited February 10, 2014 by croustiFajita Quote Link to comment Share on other sites More sharing options...
+Stephen Moss Posted February 11, 2014 Share Posted February 11, 2014 (edited) On your original diode I would think the thicker of the coloured bars would be the Cathode but could not be 100% certain of that without viewing the data sheet. Having looked at the schematic diagrams here on AA I can only find 1 Zenner diode although that appear to be labelled D12 (D13 is a 1N4148) however, it is possible this mismatch may be cause be circuit revision leading to a renumbering. That aside the schematic shows the Cathode of the Zenner goes to TP1 & R56 (120R) and the Anode goes to 0V so try tracing the PCB tracks round to work out which way to connect it on the circuit board assuming it is not indicated on the PCB itself by either the arrow & bar diode symbol or a rectangular box with the thicker filled section at the cathode end. Edited February 11, 2014 by Stephen Moss Quote Link to comment Share on other sites More sharing options...
+karri Posted February 11, 2014 Share Posted February 11, 2014 The problem with Lynx power is that when it blows it may brake other chips as well. Usually the regulation is gone and you get raw 9V on the 5V rail. Sometimes a chip act like a fuse and short-circuits the 5V to ground. The is several zero ohm resistors on the board for easier troubleshooting. We should really write a troubleshooting guide... My guess is that the caps are also all dried up by now and need replacing. Same goes for the LCD. But just changing a zener to get it going sounds a bit optimistic. I wish you luck. I have not used zeners much so I cannot help with this type. Quote Link to comment Share on other sites More sharing options...
croustiFajita Posted February 11, 2014 Author Share Posted February 11, 2014 Hi Stephen, Karri, and thank you for your answers ! I'm beginning to loose hope about this Lynx .... I've already changed every caps on the board, and also changed the Q12 mosfet, and all I can get is a blank screen by short circuiting the ground of the jack and the batteries ..... You're probably right Karri, 9V may have fried Mikey or Suzy, so it's hopeless. I managed to bring back to life my old GameGear and my old GameBoy, just by replacing all the caps, so maybe I was too optimistic about repairing a Lynx, this baby seems to be harder to awake ! When I'll have some time i'll remove the shielding and I'll inspect the board with a magnifier to seek any component which seems burnt. Anyway, thank you for your replies Quote Link to comment Share on other sites More sharing options...
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