New power supply for my Mega ST4

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rcamp48
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New power supply for my Mega ST4

Postby rcamp48 » Fri Mar 22, 2019 3:47 am

Today with a little help from a friend , a new Meanwell power supply was installed in place of the 30 year old one in it, this Meanwell power supply has a strip of screw connectors on it, all you have to do is cut the wires on the power plug and solder new longer wires to the connectors on the power end, the white wire goes to the neutral screw on the new power supply, the black wire goes to the Live screw (110 or 220 Volts , the power supply automatically switches).

As for the 5 volt and 12 volt connections, the red wires are positive and 5 Volts , then go to the +5V screw on the strip, the other color (varies) goes to the 12 volt terminal, the black wires are neutral, they go to the common screw on the 5 and 12 volts screw strip.

The fan on the Mega ST has a red wire on it , you would think, hey thats 5 volts, but NO , it is 12 volts., you would connect the red wire from the fan to the +12 Volt terminal , and the black wire to the common terminal.

They say that 2 picture are worth 2000 words, so I will show you 2 pictures of the Mega ST4 working , one showing up close the new power supply, the other showing the output screen from the VGA cable. Russ

psu.jpg


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Re: New power supply for my Mega ST4

Postby 6BQ5 » Fri Mar 22, 2019 7:34 pm

+1!

Those Mean Well supplies are small and powerful.

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Re: New power supply for my Mega ST4

Postby charles » Fri Mar 22, 2019 11:02 pm

where on earth can we aquire some more of these power supplies?
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Re: New power supply for my Mega ST4

Postby 6BQ5 » Fri Mar 22, 2019 11:10 pm

I bought my Mean Well supplies from Digi-Key but they are easily available on Amazon, eBay, Mouser, etc.

I used a RD-60A in my STe.

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Re: New power supply for my Mega ST4

Postby charles » Sat Mar 23, 2019 12:37 am

many thanks
question:
will any generic atx do the trix?
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Re: New power supply for my Mega ST4

Postby 6BQ5 » Sat Mar 23, 2019 5:36 am

charles wrote:many thanks
question:
will any generic atx do the trix?


Generally speaking, any power supply that matches the voltage and current specs of the original supply will work. The ST doesn't need a lot of power. I can't remember the exact numbers but I think you only need 3A for the 5V feed and 1.5A - 2A for the 12V feed. That's a combined power output of 40-ish Watts.

ATX supplies are more than capable of powering a ST machine. The problem may be fit. I can't imagine an ATX supply that would fit inside the case. Perhaps you could run it externally? It could be a fun project and a good way to dive into the internals of your ST if you feel inspired. Personally, I say the path of least resistance is a small and simple power supply available off-the-shelf. 8)

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Re: New power supply for my Mega ST4

Postby swatcop » Tue Jun 25, 2019 5:01 pm

Saw the OP's post as well as Jan Beta’s video and decided to give it a go. Jan's video glosses over a few things - like the common (black) ground wires. Theres a lot of them. Looks like Jan just randomly bundled them and ran them to two brown wires (he didn’t have any black) and ran them to the Mean Well.

My question is: are all the common black wires interchangeable or are they specific to 12v and 5v or can you run them randomly to the black wire/s connected to the Mean Well? My thoughts are there would be a 12v common and a 5v common to complete a circuit with set voltage? I should have paid more attention to the electrical portion of Science class in school :wink:

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Re: New power supply for my Mega ST4

Postby charles » Tue Jun 25, 2019 9:04 pm

voltmeter is your friend
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Re: New power supply for my Mega ST4

Postby swatcop » Tue Jun 25, 2019 9:35 pm

charles wrote:voltmeter is your friend


Right Charles, but I don't have a working MegaST PSU to compare what its doing against the new PSU or a wiring schematic (that I could find at least) to refer to. Was hoping someone who had done this mod might chime in. Will definitely test with a multimeter before even a single lead is connected to my Mega.

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Re: New power supply for my Mega ST4

Postby 6BQ5 » Tue Jun 25, 2019 9:40 pm

charles wrote:voltmeter is your friend


Also, find a schematic online. Google can help you with that. Your VOM readings ought to match the schematic.

Going off of memory here, my motherboard STe uses a common ground between +5V and +12V. My Meanwell supply has two ground terminals but the STe motherboard had three ground wire connections. I had to connect two ground wires together.

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Re: New power supply for my Mega ST4

Postby swatcop » Mon Jul 01, 2019 3:07 am

Image
This was a great lesson for me on how power supplies work and the value of a good multi-meter. Ground is... ground. My Mega ST is up and running and life is good. These Mean Well PSU’s (so far) are stable and seemingly perfectly suited for replacing the 30 year old power supply in my old ST’s.
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