Recent content by dorke

  1. dorke

    Tek 475 scope

    Well Corri, As the saying goes :"You can't teach an old dog new tricks ",it goes without saying, nor any wisdom either. Best of luck.I'm out of here.
  2. dorke

    Tek 475 scope

    No, I wouldn't remove the transformer before making sure it is faulty in-circuit. The fact that you don't have most voltages doesn't point to the transformer itself as the fault. That is so since most voltages are regulated in the 475 scope, they are created using IC's which work from some...
  3. dorke

    Tek 475 scope

    Well, there is a layout photo on the manual,it isn't clear enough. The caps are connected to the rectangular bridge rectifiers "+" and "-" pins. If it is easier you can check on these instead. Look at the photo attached. If you can,please take a clear photo of the actual board, it will be of...
  4. dorke

    Tek 475 scope

    The Primary looks fine. I'm assuming the voltages you have tested are all on TPs(Test points). To check the transformer secondary,please check the DC voltages on : C1412,C1414,C1442,C1452,C1462,C1472 (both probes on each capacitor,careful not to cause a short!). Please don't check HV noted...
  5. dorke

    Tek 475 scope

    O.K. I see you have a Fluke DVM, which is excellent. If you are convinced there is nothing on the secondary of the main transformer(hope you checked AC voltages),we should check the primary: Please refer to ch. 11-power supply , under Diagrams and Circuit boards. The first thing to do is to...
  6. dorke

    Tek 475 scope

    Hi Corri, As always,good notes and advise from @Hop :cool: Well there are a few members here over 80. I'm not one of them,but am not a "spring chicken" either :) I'm willing to help you fix the scope "on-line" (it will take time), Since If the scope is totally not working it is most probably...
  7. dorke

    EP-613 linear reg. power supply ,looking for service manual or schematics.

    It's Linear.
  8. dorke

    Tek 475 scope

    This scope is an excellent 200MHz analog CRT of times passed(early 70's),was the top of the top at it's time. I own a 465 which is 100Mhz and was the standard scope for pros in the 70's. It is also a very complicated device to fix even for Pros. You may be lucky and the problem might be a...
  9. dorke

    EP-613 linear reg. power supply ,looking for service manual or schematics.

    Yes,I can do that. I can also create a full diagram by tracing the devices and boards etc. but I rather have the diagram instead of all that work and time...:)
  10. dorke

    EP-613 linear reg. power supply ,looking for service manual or schematics.

    I recently got this linear triple power supply 0-30V/2.5A variable,12v/5v fixed. Need the service manual or schematic in order to repair and calibrate it. It is sort of a generic/label unit goes under various names Manson/Rapid/Velleman/OF.I etc. I searched the net ,couldn't find it. Does...
  11. dorke

    What should I get for beginning electronics?

    Welcome to EP. If you are serious about learning electronics, the place to start would be learning the theory of electronic circuits. There are good books for beginners,many on the web. Building things like "kits" isn't really learning and understanding how things work. After you have gained...
  12. dorke

    MOSFET burning up but similar circuit on another board is fine

    Welcome to EP. You identified the problem correctly : the Mosfet doesn't saturate. But your solution is wrong: 1. You can't operate a 74ACT04N or a 7404 at 3.3V they need 5V VCC(they are speced at 5V). 2. In any case, a logic device operated at 3.3V VCC can't produce an output higher than...
  13. dorke

    WD My Book Duo NAS WD10000D033 - No Power

    Your welcome. Look closely at your power adapters. They are both 12V, but one can supply 4A while the other only 1.2A, that is a significant difference.
  14. dorke

    Series bulbs with rectified AC

    Thanks Harald for the correction! 0.7 it is.
  15. dorke

    The LED is lightly glowing when switch off state. Please explain

    Looks like you don't quit understand this circuit. "When V1 is 3.3V, the output of the transistor Q2 will ON and get the 3.3V at the collector and D2 LED will glow." WRONG! But D2 will glow. That is because it will conduct through the collector of Q1. Q1 is on,Q2 is off. "When V1 is 0V, the...
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