TV power supply

I wonder if anyone can help - I have a 15 inch lcd tv with digital freeview receiver. They each have their own power supply adaptor, one at 12v - 4.2amp and the other at 12v - 1.25amp output. Becauase of the lack of space where the tv sits I wanted to run both tv and digibox from the one power supply adaptor. Is this possible/safe to do and which supply do I use - 1.25amp or 4.2amp?

Thanks

Tommaz

Reply to
tommaz
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Absolutely not. The 4.2 Amp power supply is highly unlikely to have been designed with a safe extra 1.25A capacity, and connecting both appliances to it is sure to kill it. The smaller supply doesn't even have half the capacity that the LCD requires, so it goes without saying that it won't run both applainces!

Dave

Reply to
Dave D

Thanks for that Dave

Is there another way of reducing the clutter? If I can get hold of a power supply of say 5.5A capacity would this allow me to run both appliaces from it?

Tom

Reply to
tommaz

Use an RV car battery + charger, that'll supply enough current and top up the charge overnight when you're not using it.

Reply to
I.F.

You could try hiding the supplies behing the LCD and using some cable tidying accessories like that spiral flexi conduit stuff to shroud the wires. How bad can a couple of small SMPSs be? There must surely be a way to hide them somewhere.

Yes, that would work, but the supply would likely be bigger than either of your existing supplies, what would you gain?

Dave

Reply to
Dave D

Just so I'm clear - if I use the 12 volt leisure battery in my caravan (hence the restricted space), then all I have to do is wire the TV and digibox direct to the 12 volt supply? Do I need to put any in-line fuses in place first or will the TV and box just take as much current as they need?

Thanks

Tom

Reply to
tommaz

Your LCD and digibox will likely want a very stable 12V supply, and a battery will not offer that. Unless the appliances are explicity designed for battery use, forget it. They will simply malfunction when the battery starts to deplete, or worse it may cause damage.

No offence, but by asking a question like that you demostrate that you really should leave things as they are and forget about experimenting with expensive electronic appliances!

Fuses are not current limiters the way you think, they are a failsafe device to protect an appliance when either the power supply fails or the device itself develops a fault. They prevent catastrophic damage in the event of a short or fault condition and do not 'limit' current to a normally working device.

Yes, you most certainly should use a fuse inline if you're going to experimentvlike this! A 5 Amp fast blow fuse should be OK, but if you create a situation where the fuse blows, it's unlikely either the LCD or the digibox will survive anyway.

Dave

Reply to
Dave D

Thanks for the advice Dave

I'd rather keep thind as they are than blow a perfectly good TV.

Tom

Reply to
tommaz

Dave D spake thus:

No offense, but technically speaking, fuses *are* current limiters; it's just that they can only perform that function once when the current exceeds their rating.

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Pierre, mon ami. Jetez encore un Scientologiste
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Reply to
David Nebenzahl

Dave D spake thus:

Damage from *undervoltage*?

Please be so kind as to explain how this could possibly happen.

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Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.
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Reply to
David Nebenzahl

It can sometimes happen with badly designed SMPSUs, I don't know why maybe its something to do with excessive duty cycle. Many currently available SMPSU controller chips have UVLO which is considered a vital safety feature!

Reply to
I.F.

That's what I said, did you even bother to read the OP's post and my*full* reply before putting your foot in your mouth?

Dave

Reply to
Dave D

TFTs often have small onboard SMPSs to drop the 12V down to 5V and sometimes other voltages as well. SMPSs can pulse/cycle when the input voltage drops below a value at which they can maintain a stable output, which can damage the SMPS itself or the rest of the panel's electronics.

HTH.

Dave

Reply to
Dave D

Each unit must run on its own supply. These supplies are current rated for one unit only. If you can find a single supply that is of double the current rating, then using 2 units on one supply should work. But, you will be back to your space problem again, because the double rated supply will be physically much larger.

There is the other senerio, where dedicated supplies can have particular safety sensing for the one unit that it is supposed to work with. By using another type of supply, this safety aspect will be defeated. This can lead to another set of problems.

If you are using the monitors for commercial purposes, and need to have space savings, get them changed to monitors that have built in supplies. This may be the best alternative for you.

You can't get around the laws of physics!

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JANA

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