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Can somebody help me decipher the DotCom QSP-1 AC input pins
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Author Can somebody help me decipher the DotCom QSP-1 AC input pins
Bryan B
I just bought the QSP-1 power supply for my brand new modular and now I would love to wire up a fuse, on/off switch and AC connector to start getting things powered up.

I am building a custom acrylic case, so I wanted to mount the AC input and power switch nicely into the case instead of using up one or more of my spaces for power modules.

Disclaimer: I know this is potentially dangerous for me (or anyone else) to do, but I have worked on multiple projects using AC and I make time for saftey and I am usually overly cautious when it comes to working with high voltages.

The AC input connector has 4 unlabeled black wires and one green. There is no pin info on the website and a few hours of searching the web has yielded no fruit. My best guess is that the four black wires are for 110AC and 220AC inputs and the green is a ground.

Now which pins are for which voltage. I know that one of you knowledgeable modular veterans can answer this nooby question for me.

What size should the fuse be?

Also out of curiosity, how do I properly wire the switch for choosing 120 or 220?

Sorry if this has been asked before. Please link me to this info if you know where it can be found.

The pin numbers match the AC input numbers of the transformer on the Power One/International Power/Condor supplies (except for 5 on the harness, which is chassis ground and doesn't go to a transformer input). You can read the pin numbers on the back of the connector where the wires are coming out from. Basically:

1 is 1
2 is 2
3 is 3
4 is 4
5 is ground (green)

Since you're in the US and will probably only need 120v, you could just wire up (like I did) pin 1, 4, and 5.

This info is from Roger, and I had to e-mail him to get it. Should be on the website, don't know why. Probably afraid of people shocking themselves.
Bryan B
Thanks for the help SynthBaron! That info helps a lot.

Now to find out how many amps the fuse is. Based on the "how to build your own power supply thread, I would guess it should be a slow blow type.
As you're using Dotcom modules, I have to recommend getting a Dotcom power module, like the Q137, and a cable loom. However, you're already going the DIY route, so my advice will be a little late.

So I'll just say...Take care!
Bryan B wrote:
Based on the "how to build your own power supply thread, I would guess it should be a slow blow type.

Mine looked like a fast blow, which is what you should be using anyways. 3amp is what is in the Q137 module, but you should use whatever it recommends on the silkscreen of the power supply.

Oh, and I just want to make clear that the 5th pin is chassis ground, and does not hook up to the transformer.
Bryan B
I bought cable and connectors to build my own power cables too, and have a distribution board coming from STG coming (hopefully soon). I tested the connector last night and it appears to be something I can easily handle (as far as assembly and making sure the wires/colors/positions are all absolutely correct).

Thanks for the info on the Q137 fuse. I will still have to check if it is supposed to be a fast or slow blow before it is operational. I will look on the power supply for fuse info, good idea (that I should have thought of already)!

The green is a ground for sure and it is connected to the power supply chassis (not the transformer). Thanks for reinforcing good safety anyhow.

Thanks for all the help! I knew the Wigglers wouldn't let me down. I love this place.
Bryan B
I was excited to get my modules up and running, so I tried to hook up my power supply last night.

I had #1 and #4 (from the transformer) hooked up to AC (hot and neutral) and the green (chassis ground) to the AC ground connection. I had a distribution board hooked up (from the red, green, white and black wires) and one module connected to give it a small load. It doesn't appear to be putting out enough voltage to run anything though.

I bought this brand new and it came packed up really nice, so I was assuming it should be working. Is there any way to test my power supply to make sure that it is working properly? I would really like to make sure it isn't user error before I see what my other options are.

The AC is coming in and tested fine. I have a digital meter.

Of the 2 wires going into the transformer, does it matter which one I connect the hot wire to? Will it ruin it if I wired them backwards?

Did you jumper the transformer inputs like it says on the power supply silkscreen? You should solder a permanent wire from 1 and 3, and then 2 and 4...and then apply the AC to inputs 1 and 4.

Just hook up the 1 and 4 leads to 1 and 4 on the power supply and you shouldn't have any "hot and neutral" problems.
Bryan B
No, I didn't do that. that very well could be it! d'oh! I will try it tonight as soon as I get back home.

Thank you SynthBaron!

Does anyone know what a 2 amp fuse at 120vAC would be if there is only 250vAC fuses available? Can you use a 250vAC fuse instead of a 120vAC one?

Could I use this formula to figure this out? Watts / Amps = Volts

240Watts/2 Amps = 120 volts
240 Watts/1 Amp = 240 volts
It just means they're designed for up to 250v input. I have never seen a 120v fuse, if that helps. A power supply draws less current at a higher input voltage, so that's why a lower rated fuse is needed. So, if it says it needs 2A for 120v, that's what you use.
Bryan B
Do I have to connect/jumper 1 and 3 and 2 and 4 on the transformer itself or can I send the same signal to both? The inputs on the transformer are covered with silicon (to keep people from touching them?).

I imagine that the DotCom power module jumpers the inputs at the module with a switch because it can switch between 120 and 240. Is it wrong to think these thoughts?
You can either jumper them on the transformer, or just connect up the 2 extra wires to the Q137.
Bryan B
I just tried out the jumper thing and now it works! Thank you for helping me solve all of this.

Now to finish the wiring, so I can start making sounds.
Isn't messing with AC fun? LOL. I still hide behind the case when I turn on the switch when messing with the PS in my case.
Bryan B
No sparks, no fires, no burnt PCBs. This was a learning experience, but well worth it! I probably saved $400 by wiring everything, making power cables and building my cabinet.

I tested all of my modules with some quick patching and everything is powered up working great! The cabinet is all assembled now, but I still will have to figure out lights and possibly laser engrave some artwork on the side panels and back.
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