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BitBang Offline OP
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I'm working on a Dukane MCS350 rack and found the main 24V PS was at 32 volts. Seemed like a problem because 24V goes to relays, regulators, consoles and I didn't want components to be stressed and fail. True, board regulators get the volts down but it means there’s that much more overhead to dissipate.
I took the supply apart and it's just a transformer, bridge rectifier and big capacitor. No regulation. I opened up the transformer and there are no voltage adjust windings.
So now I'm considering replacing the stock supply with a Power One 24V 4A linear.
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A second problem: I found the 120VAC neutral is hardwired to the safety ground inside the supply. This means part of the return current from the hot side flows back through the safety ground. I plan to separate the two and connect safety ground to the chassis.
Next I need to consider the other grounds: DGND, AGND. In my opinion these should be connected, but at one point such that digital current does not flow through AGND and muck it up. Also, I think DGND should be connected to safety ground so that the electronics don’t float and drift up to some tingly voltage. Seems like the analog card would be a decent place for both connections.
Thoughts Anyone?

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The MCS350 has an unregulated power supply by design from the factory. Do not modify the power supply. Why are you considering changing the power supply?

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If it's not broken why fix it?


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BitBang Offline OP
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When you folks measure the 24V TP on a Card are you expecting 32V?

That's 33% higher.
It would be like running a 120VAC blender on 160VAC. Doesn't make sense to me.

If I measure 4.8 - 5.8 on a 5V TP that's good enough to get the job done without stressing the ICs.

Thanks for your help figuring this out. BB

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The MCS350 does not have a regulated power supply. The regulators are on the boards themselves. 32VDC is normal for that power supply output -- I just measured on my MCS350 here to double check. What exactly are you going for anyway? What trouble are you having with the MCS350 that you're disassembling the power supply??

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BitBang Offline OP
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Originally Posted by Professor Shadow
If it's not broken why fix it?

Hi Dean, Good question.
Because, if I break it, I’ll have something to fix. Very logical ya' know. greensmilies-017

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BitBang Offline OP
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Hello Tim,
I think you guys did great job answering my question. Although the PS is labeled 24V, it was designed by the manufacture to run at the higher voltage. Originally, I thought maybe that was the case, but didn’t want to assume that without being absolutely sure. The reason I took it apart was to see if there was a voltage adjustment to correct the problem or at least understand the situation better. Thanks for the confirmation and measuring your system. Now I know something new. Can’t beat that!

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Originally Posted by BitBang
to correct the problem
What problem are you trying to correct?

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BitBang Offline OP
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What problem are you trying to correct?

"to correct the problem"


A +24V test point measured +32V. That was the problem I was talking about.

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Originally Posted by BitBang
What problem are you trying to correct?

"to correct the problem"


A +24V test point measured +32V. That was the problem I was talking about.
It's not normal for me to pull out a voltmeter to test a power supply just on a whim....I've got more important things to do than chase down problems that don't exist!


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