How to test a HV diode board

Discussion in 'Amateur Radio Amplifiers' started by K5JCJ, Feb 17, 2020.

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  1. K5JCJ

    K5JCJ Ham Member QRZ Page

    Can someone explain how I should go about testing a HV diode board? I bought this aftermarket HV board set for my Drake L75 and the maker suggested I test it before installing it in the amp. Does anyone know the procedure to do this? See the photo of the board.

    I have access to a variac and plenty of parts and meters. Just not sure where and how to make the supply connections vs. test points.

    73,
    John K5JCJ
     

    Attached Files:

  2. W9WQA

    W9WQA Ham Member QRZ Page

    you could apply some low volts and see what comes out. look across each diode, the same.
    i never saw resistors on diodes but it must be right.
    heathkit huh?
    also ohm meter checks.
    you are looking for major problems,shorts,opens. not likely to find i guess.
     
  3. N8CBX

    N8CBX Ham Member QRZ Page

    I use my variac (124vac) as the AC input to test my rectifier boards and use my O-scope to monitor any problems.
    Jan N8CBX
     
  4. K5JCJ

    K5JCJ Ham Member QRZ Page

    The issue is that if you look at the board there is only one pad for AC Input and two pads for DC output. I'm not sure how to wire it up for testing.
     
  5. W9WQA

    W9WQA Ham Member QRZ Page

    its a doubler circuit.
    look up one or hook it to your amp,pull tube and bring up ac line slow.
    i dont know your amp.
    or get local help...
     
  6. W1QJ

    W1QJ Ham Member QRZ Page

    What you have here is a doubler rectifier, nothing more, nothing less. It works in tandem with the capacitor bank. All you need to do is check the diodes with an VOM on diode check. If they test good then you are good to go. Install this in place of whatever diode board is in the amp now. Done deal.
     
    K8PG likes this.
  7. KM3F

    KM3F Ham Member QRZ Page

    My curious! The board has an assembly date of last year and looks unmounted.
    Why is there a question unless it is a reject. If this is the case, shame on the seller.
    All you have to check is Diodes for shorts or opens and front to back ratio.
    No need to fool with applying power unless your determined to do that, then what are you looking for as a fault?
    Same difference; a diode that has failed using the same test you meter does, without powering up the assembly.
    Good luck..
     
  8. K5JCJ

    K5JCJ Ham Member QRZ Page

    The board was sold to me unpopulated. I added the parts.
     
  9. K7TRF

    K7TRF Premium Subscriber QRZ Page

    As others have posted, just check each diode with an ohm meter. You should read a nominally low resistance (e.g. 500-700 ohms) in the diode's forward direction and should read the value of the voltage equalizing resistors (150 k ohms) in the reverse direction.
     
  10. K6BSU

    K6BSU Ham Member QRZ Page

    Reading forward resistance with an Ohmmeter is OK, but different meters will give different values. My Simpson 260 will typically read a power diode 20-40 Ohms forward. Depends on loop battery voltage and meter sensitivity.
     
    AI3V likes this.

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