What transformer should I use?

Hello,

I have 4 transformers and 4 modems.

Two with 9V and 1A output and two with 12V and 1.5A output.

Which "unique" transformer should I put to eliminate the 4 transformers coming from the factory with each modem? What output should it have? I want to save the space they occupy.

ATTACHED DRAWING

OR if not possible with one transformer then with two.
one for the two modems of 12V 1.5A
and one for the other two modems of 9V 1A
Or, could I get rid of one of the stock transformers (same OUTPUT) and use it for both of the modems? Will it work?



Thank you!

It's possible that the power input connector is connected internally to some of the inputs or outputs of the device. If it is then sharing PSU might create a loop which may or may not be harmful. Sorry its all "maybe's", but it's impossible to know.
You clearly need two supplies, a 9 volt and a 12 volt.
If you try running two in parallel then there are three possible outcomes. It may work fine, it may malfunction but no damage, or it could cause permanent damage.
You may find better help and guidance on an IT oriented forum, where someone may know what's inside the modems.

As a blind guess, and that's all it is given the limited info,
One 9v 2 amp transformer should power the 2 9volt modems, and a 12volt 3amp should power the two 12volt modems,
To be on the safe side I'd slightly over spec and get 9volt 3amp and 12volt 4amp ,

You could try the 12V modems on a 9V power supply. You might just find they work and then you can use one power supply. Very often the external supply is unregulated and the modem contains a voltage regulator almost certainly down to 5V or even 3.3V

DO NOT try the 12V supply into the 9V modems, that might not end well.

Remember using anything other than the supplied power adaptor will invalidate any warranty.

4 way adapter?

Just saying..................

I thought
1) You will have to spend some money to get two transformers.
2) You will spend time looking for these transformers.
3) Chances are to get a 9v 2A transformer and a 12v 3A Transformer, you will get "Skeleton" power supplies (They are good)
3a) "Skeleton" power supplies must have an enclosure. (More money, and take up more space.)
4) You want two, but more powerful power supplies, I would say they will be bigger than what you have.
5) Using non-genuine parts invalidates your warrantee.
6) If one power supply fails, you lose 2 modems.
7) It's a nice idea, but too much cost/effort for too little gain.
8) I would move the existing power supplies.

But I have now checked, you can get a 9v wall wart, and a 12v wall wart for less than £10 each, cable splitter £2.50 each, but 1,2,5,6,7 & 8 still apply

Thank you all!

I would expect that the supplies which came with the modems are internally fused to suit all expected fault scenarios in that particular modem.

I would be wary of connecting a power supply capable of more current.

Chrisbee said:

I would be wary of connecting a power supply capable of more current.

Click to expand...

Why,?
The device will only draw the current it requires.

I agree with you steptoe, I would also suggest that the power supplies have no fuses at all, and I also doubt the OP is worried, since his last post does not ask questions.

That's correct and will work fine, probably for ever.

But the power supply should be designed so that in the event of a fault in the modem or beyond, an internal low voltage DC fuse would blow rather than modem components getting hot or even starting a fire.

Just the same as protection back at a mains CU would protect the installation it supplies.

PS. I'm not talking about a replaceble fuse, but possibly a fusible resistor soldered into the board, a self resetting one or other current limiting design built into the electronics.

Just food for thought. That's all.

"Should be designed"

In an ideal world, yes, but this is a "Build it cheap as you can" world, (Not to mention, it is nothing like a CU.)