Electronics Question

Phil №❶ · **May 17, 2014, 11:11:15**

I need to replace a DC plug pack, the label says 100 - 250 v 0.3A, so how do I calculate the correct replacement part. Is the 0.3 @ 240 or what.

Thanks in anticipation.

asathorny · **Reply #1: May 17, 2014, 11:22:55**

If ya wet yer finger Phil and stick it in the hole where the live wire is............................ JUST KIDDING

I have no idea

Phil №❶ · **Reply #2: May 17, 2014, 11:25:38**

CraigB · **Reply #3: May 17, 2014, 11:52:32**

0.3A will be the output needed for the item you are powering/charging, 240V is the Australian compatible voltage input... is that what you needed?

Phil №❶ · **Reply #4: May 17, 2014, 12:01:29**

It will do, but how does a plug pack manufacturer know what the power requirement of a device is. That's putting the chicken before the egg.

Now to try and find one with an Oz plug.

CraigB · **Reply #5: May 17, 2014, 12:06:08**

I got that slightly wrong sorry, the input for the power pack is 240V = 0.3A = 50/60Hz

you just need to match the output to what you device requires.

Phil №❶ · **Reply #6: May 17, 2014, 12:08:13**

Roger that.

TheReaper · **Reply #7: May 17, 2014, 12:30:17**

The Gonz · **Reply #8: May 17, 2014, 14:49:11**

The 0.3A will be the maximum across the range of 100-240V, or 72VA (W).
The same capacity once through the conversion - assuming no losses (which is highly unlikely) - will deliver 6A if your plug pack does 12V, 8A at 9V.

This still seems very high to me and the current is usually stated for the output, not the input.
How big is this device and what is your output voltage?

CraigB · **Reply #9: May 17, 2014, 17:48:14**

Quote from: The Gonz on May 17, 2014, 14:49:11

How big is this device and what is your output voltage?

Going by the amps and voltages given I'd say it's a phone charger

it's the same input levels as my IPhone charger ( output is 5V - 1000ma )

tla · **Reply #10: May 17, 2014, 20:23:42**

I think the 100-250V rating simply indicates that it can be used in most (all?) country power supplies, e.g. 110 in US, 240 in Aus, 220 in China, etc.

0.3A is the maximum current that can be supplied by the transformer. So, you can replace it with a similar DC plug pack that supplies 0.3A or more.

Phil №❶ · **Reply #11: May 17, 2014, 23:28:13**

It is the power supply for the masthead amplifier, I highly supect it is intermittently faulty as we lost all but the community station on Friday night. It is supplie in the ceiling by a light circuit source and on resetting it, the stations all came back, been fine since then.

The Gonz · **Reply #12: May 18, 2014, 01:08:49**

Quote from: tla on May 17, 2014, 20:23:42

I think the 100-250V rating simply indicates that it can be used in most (all?) country power supplies, e.g. 110 in US, 240 in Aus, 220 in China, etc.

Yes, most 'smarter' supplies do that now with the use of internal electronics including switch mode.

Quote

0.3A is the maximum current that can be supplied by the transformer. So, you can replace it with a similar DC plug pack that supplies 0.3A or more.

The devil is in the detail. Take care when stating 'maximum current' because it's different before and after the transformation, which is why the 72VA would tell the story, not the 0.3A (unless we know the output voltage, which we don't yet).

I hope it's resolved for you in any case, Phil. Watch ambient temperature for items installed in ceilings.

rustynutz · **Reply #13: May 18, 2014, 01:49:18**

Geez, and here's me thinking any plug pack would do as long as it had the correct plug at both ends and was putting out at least .3A...

The Gonz · **Reply #14: May 18, 2014, 01:51:22**

Quote from: rustynutz on May 18, 2014, 01:49:18

Geez, and here's me thinking any plug pack would do as long as it had the correct plug at both ends and was putting out at least .3A...

Really? No concern for output voltage? That's like not caring whether you load your flashlight with 2 batteries or 200!

rustynutz · **Reply #15: May 18, 2014, 03:07:35**

Yes, of course I'd be taking in account the output voltage...just forgot to mention that bit.

The Gonz · **Reply #16: May 18, 2014, 03:25:19**

tla · **Reply #17: May 18, 2014, 04:40:47**

Quote from: rustynutz on May 18, 2014, 01:49:18

Geez, and here's me thinking any plug pack would do as long as it had the correct plug at both ends and was putting out at least .3A...

Are you sure that it doesn't indicate the output voltage? If you have a volt meter, can you check the output voltage of the plug pack. I suspect that it's 12V.

tla · **Reply #18: May 18, 2014, 04:44:09**

Quote from: The Gonz on May 18, 2014, 01:08:49

Quote from: tla on May 17, 2014, 20:23:42
I think the 100-250V rating simply indicates that it can be used in most (all?) country power supplies, e.g. 110 in US, 240 in Aus, 220 in China, etc.
Yes, most 'smarter' supplies do that now with the use of internal electronics including switch mode.
Quote
0.3A is the maximum current that can be supplied by the transformer. So, you can replace it with a similar DC plug pack that supplies 0.3A or more.
The devil is in the detail. Take care when stating 'maximum current' because it's different before and after the transformation, which is why the 72VA would tell the story, not the 0.3A (unless we know the output voltage, which we don't yet).

I hope it's resolved for you in any case, Phil. Watch ambient temperature for items installed in ceilings.

Yes, I made the assumption that it was a standard 12V plugpack power adapter.

Phil №❶ · **Reply #19: May 18, 2014, 05:52:58**

This is a good discussion fellas and partially why I asked, because I wasn't sure what was being stated.
My understanding of current output is that it is voltage dependent, so @ 100v the current would be higher than @ 240, so is it 0.3 at 100 or 240V.

@ 100v x 0.3 = 30 watts

@ 240 x 0.3 = 72 watts

Assuming a watt is a watt, 240 represents more work than 100

BTW the plug pack says 14V not a simple 12V one. Harder to find.

The Gonz · **Reply #20: May 18, 2014, 06:02:44**

Regardless of the input voltage you apply, I expect the current limitation will be inherent in the design of its output. The usual plugpacks will state the current draw at the designed output voltage, so my assumption would be that your 14V supply will cope with supplying up to 300mA. Given that supplies don't push more than devices can draw, I'm still finding it odd that this might be considered the supply's drawn current and not its available current.

Got a link to its specs? Identifying data? Picture of the label?

Phil №❶ · **Reply #21: May 18, 2014, 06:05:53**

Next time I'm in the Roof I'll photo it. I am going to mount the replacement one on an outside wall where the ADS-B Plugpack is and run a fairly lengthy wire to the masthead amp. The ambient on the plugpack will be greatly reduced.

The Gonz · **Reply #22: May 18, 2014, 06:08:17**

By the way,

rustynutz · **Reply #23: May 18, 2014, 06:29:37**

Is the plug pack anything like this, Phil?

Kingray PSK06 Plug Pack 14V DC 150 MA Power Supply Injector FOR Booster Amplifie | eBay

Phil №❶ · **Reply #24: May 18, 2014, 06:36:56**

Yes, the design is similar in that it goes to the molded amplifier socket, I will have to cut this wire to add a new plugpack. Note that the listed device quotes a voltage and output after conversion, not before. According to me 14V X 150ma = 2.1 Watts. My device is 72 watts.

rustynutz · **Reply #25: May 18, 2014, 07:49:21**

Might be easier to just buy a whole new masthead amp and power supply.....

rustynutz · **Reply #26: May 18, 2014, 07:55:52**

This any good?

TV Masthead Amplifier Kingray UHF VHF MHW24F PSU PSK06F F OR PSK06PAL Digital | eBay

Phil №❶ · **Reply #27: May 18, 2014, 08:04:35**

I don't think so, needs to be 4 outputs.

rustynutz · **Reply #28: May 18, 2014, 08:05:35**

rustynutz · **Reply #29: May 18, 2014, 08:07:32**

Wouldn't you just have one output which then goes to a 4 way splitter?