Astron RS-35M Not working after Lightning Storm

Discussion in 'General Technical Questions and Answers' started by NU9S, Aug 21, 2018.

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  1. NU9S

    NU9S Premium Subscriber QRZ Page

    Yes I removed the board enough to see number one then counted the way you said. The chip has 14 pins 7 on each side so the third one down the second side is pin 10. I also posted a photo of a small capacitor that has a burn mark on it did you see that photo?

    KA9JLM likes this.
  2. NU9S

    NU9S Premium Subscriber QRZ Page

    Ok I was wrong it is .10 volts at pin number 10. I measured the wrong pin and whn I went back and looked at it I was backwards sorry.
  3. KD3WB

    KD3WB Ham Member QRZ Page

    There's a good chance that chip is defective. Glad to see it's in a socket and not soldered directly to the board. If you decide to order one, please note that the LM723 comes in several different packages, so be sure to search for "LM723CN". Also, I looked at the picture of the burnt-looking capacitor. It looks like it's a non-critical bypass capacitor and I doubt if it's causing the problem.

  4. KD3WB

    KD3WB Ham Member QRZ Page

    Also, be sure to insert the new chip correctly. They're symmetrical and can easily be inserted backwards.

  5. NU9S

    NU9S Premium Subscriber QRZ Page

    Where is a good place to order one of these?
  6. K7JEM

    K7JEM Ham Member QRZ Page

  7. KD3WB

    KD3WB Ham Member QRZ Page

  8. AI3V

    AI3V Ham Member QRZ Page

    Sorry I disappeared, I got 3 emails then they stopped.

    The lack of voltage on pin 10 almost certainly means the chip has failed.

    It is not providing the signal to turn on q2, which drives the heatsink mounted pass transistors.


    P.S. you did have everything disconnected from the power supply while measuring?:)

    Pps, Just to be sure, pin 10 is next to the letter "c"
    Last edited: Aug 22, 2018
  9. NU9S

    NU9S Premium Subscriber QRZ Page

    Yes everything was disconnected from the power supply when measured. I ordered a new chip so we will see if that's what's wrong or if something else got taken out also. I will keep my fingers crossed .
    AI3V likes this.
  10. AI3V

    AI3V Ham Member QRZ Page

    Some sort of resistor,

    For a field expedient substitute, try a very low wattage 115v incandescent bulb, something like the little fancy ones for night lights.

    Never assume a capacitor is discharged, measure it!

    And BE ABSOLUTELY SURE to watch the voltage drop, DO NOT make the mistake of a meter reading zero, that you haven't just seen reading ok, actually being right.

    A broken voltmeter, and a open bleeder resistor can ruin your day.

    After you do the above, a screwdriver (chicken stick) across the cap.


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