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Troubleshooting Older Dynasty DX

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  • Troubleshooting Older Dynasty DX

    I have an older Dynasty DX, SN KJ091088, that was sitting around for quite some time due "to some board issues." I replaced the buss caps and all pre-power checks are good, but I haven't powered it up yet because it looks like the clamp board (PC8) got a little hot under R16 and R17, which look like they carry the output voltage and are in series with the clamp circuit. For all of those who ever worked on these, is this common? The circuit board looks cloudy right under the resistors when held up to the light, kind of like it was charred. The leads right around the resistors are discolored too. All resistors and capacitors check out ok, and there are no shorts in the diodes or ICs. I am thinking of powering it up and putting an RV water heater element (1 ohm) across it to function check.

  • #2
    You'll be a whole lot better off load testing into a drywall bucket full of salt water.

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    • #3
      Can you use a paint bucket or a cat little bucket or does it have to be a drywall bucket?

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      • #4
        Makes sense, though I have only tried the salt water loads with higher voltages and lower currents (higher resistance) on a couple PFC circuits. I guess more salt, and closer and bigger electrode plates gets me to the resistance I need. One of the function checks in my Thermal Arc 400GMS Service Manual is to clamp the output across a 3ft section of steel to check the output current from min to max. I know Miller makes calibrated load banks, but this welder is more of a project and less of a tool, and so far I'm only $120 total into it.

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        • #5
          You can't buy a carton of smokes In Alberta for $120 bucks...but if you go looking, you can buy an ounce of BC bud for that money. I'm just saying...it goes up in smoke so what? At least you had fun, maybe even learned a thing or two? And at the end of the day, probably ends up the cheaper habit of the three to keep going.

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          • #6
            Long as the bucket isn't conductive it'll work

            Use a couple lead springs or old mower blades for electrodes. Surface area matters.

            10 feet of 1/8 x 1 flat steel will last a while at 100 amps, but it'll get hot and wimpy. It also becomes scrap after using it as a load.

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            • #7
              Thank you for the perspective Noel, though the day job keeps me from smoking anything. Franz, thank you, I'll see what works and try it with a mains transformer welder first!

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              • #8
                After looking through the tech manual and patent # US5783799, I finally understand how the tank circuit controller works for the half bridge and how the clamp circuit feeds the switching spikes from the HF board and output inverter back into the DC buss capacitors. PC8 looked good under resistors R16 and R17, the conformal coating was a little burned, but no issues in the fiber or soldermask. I resoldered R16 and R17 with a little standoff. When I turned it on, the display just showed the decimal point without any other numbers- tracked it down to a bad ribbon connection (RC1) on PC1. All works well again. Thank you for all of the help!
                Last edited by jjohn76; 05-27-2019, 01:14 PM.

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                • #9
                  Had to be my clarification question on the bucket type that was the catalyst in this solution. Happy to help.

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                  • #10
                    Originally posted by jjohn76 View Post
                    After looking through the tech manual and patent # US5783799, I finally understand how the tank circuit controller works for the half bridge and how the clamp circuit feeds the switching spikes from the HF board and output inverter back into the DC buss capacitors. PC8 looked good under resistors R16 and R17, the conformal coating was a little burned, but no issues in the fiber or soldermask. I resoldered R16 and R17 with a little standoff. When I turned it on, the display just showed the decimal point without any other numbers- tracked it down to a bad ribbon connection (RC1) on PC1. All works well again. Thank you for all of the help!
                    By all accounts, it turned out to be the cheaper habit. Good on you for a happy ending, and also sharing so with us!

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