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Dynasty 200SD low buss voltage

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  • jjohn76
    replied
    A follow-up, I worked out most of the buck-boost circuit on the attached schematic. It looks like the reference voltage comes from D8, which is a 1N4742A (12V zener diode). I think I am missing something or the technical manual should show -12V for Pin 8 on RC1. Someday I will get a schematic program loaded to make these easier to follow.

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  • jjohn76
    started a topic Dynasty 200SD low buss voltage

    Dynasty 200SD low buss voltage

    Hi, a buddy brought his Dynasty 200SD, SN LE151928, because the front panel wouldn't light up. After going through the pre-power checks, I powered it up and found the buss voltage is only 325VDC. So I checked out the boost board, PC10, Assembly 200841.

    The only issue I found on the board is -12V instead of -15V (tech manual ref value) on Pin 8 of RC1. It is EXACTLY -12V which makes me wonder if it should be -12V. It's also a clean voltage, with very little ripple. Has anyone else seen this on their board? It powers the boost circuit current sense (HD1 on andPC2) and negative bias for off switching on boost IGBT, so I don't really want to power it up without verifying this voltage first.

    I also found the input relay on PC2 was fried (back left corner, picture below) which wasn't linking the boost inductor circuit to the main lines. For those who have a buss voltage of only 325V, this could also be the issue. To check it, I pulled PC10 and put 24V across Pin 5 and Pin 6 on connector RC10, making sure I heard the relay click. I checked the resistance across Pin 12,RC1 and L_Input on PC2. Mine read 200 ohms, which means the relay didn't close. Hopefully this saves someone some time down the road...
    Attached Files
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