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. N3AB

    N3AB Platinum Subscriber Platinum Subscriber QRZ Page


    Now that you mentioned it, the last Astron I repaired which had the bad 723 was reported to me as not turned on, yet it failed to power up when the guy went to use it. Not sure if it was unplugged or not.
     
  2. NU9S

    NU9S Premium Subscriber QRZ Page

    To replace the LM723 do you just buy the whole board or just the chip?
     
  3. KD3WB

    KD3WB Ham Member QRZ Page

    As mentioned by another poster, A1 is the regulator chip. It is probably on the underside of the green circuit board mounted between the two rows of contacts near the center of the board. The pins of an integrated circuit chip are numbered counting clockwise when viewed from the bottom, which is what you are looking at. The problem is that you need to identify the number one pin, which probably can only be done from the other side of the board. If you decide to unbolt the board, be sure to label the wires attached to the bolts and be extremely careful, since the capacitor to which it seems to be attached stores a tremendous amount of charge which can remain even when the supply is unplugged. Once you have identified the number one pin, reinstall the board, power up the supply and you can measure the pin voltages starting at number one and counting clockwise. As mentioned by someone else, pin ten is the one that actually controls the output voltage.

    Ben
     
  4. NU9S

    NU9S Premium Subscriber QRZ Page

    what is the safest way to discharge the caps?
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Just the chip! It's available everywhere.
     
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Turn the supply off, unplug it and wait a while.

    It's low voltage, so it can't hurt you, although the peak current could be very high and cause a big spark, like shorting out a battery.

    For low voltage stuff like that I don't even bother discharging caps, I just make sure I'm not wearing any jewelry -- the discharge current can be high enough to actually "weld" conductors like jewelry. But the voltage can't kill you, and probably not even cause a mild shock.
     
  7. KS4W

    KS4W Ham Member QRZ Page

    Getting a metal watch band (think late 1970's) across 12 V can cause a blister to develop on one's wrist. Don't ask me how I know!
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I know it can.

    That's why I don't wear any jewelry when working around high current sources like car batteries.

    They can't electrocute you, but a burn is very possible.
     
  9. NU9S

    NU9S Premium Subscriber QRZ Page


    Pin number 10 has 28.2 volts from the pin to ground. Does that tell you anything?
    Jim
     
    AI3V likes this.
  10. KD3WB

    KD3WB Ham Member QRZ Page

    If that is correct, the chip is shorted out.
    When counting the pins from number one, go down the row, then jump straight across to the other side and count up the other way, like going in a circle.

    Ben
     

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