Advice on testing a trasnformer

macafee2 · 2nd October 2018, 16:31

just back from holiday and found my cctv has gone wrong.
I need some advice on testing a transformer/power supply. The label on the back calls it a switching adaptor. model FJ-SW4802000F
240v input. The output should be 48v DC, 2000mA.
should I get a fixed AC voltage reading? I think not but I do.

thank you

macafee2

kaiser · 2nd October 2018, 16:38

I would expect what it says on the box. 48V DC.
A bit above or a bit below would not surprise me.
If AC maybe a blown diode or rectifier.

But what did you measure?

macafee2 · 2nd October 2018, 17:02

Quote:

Originally Posted by kaiser

I would expect what it says on the box. 48V DC.
A bit above or a bit below would not surprise me.
If AC maybe a blown diode or rectifier.

But what did you measure?

I think in excess of 100v ac. if this means the transformers duff I hate to think what it has done to the unit it powers

macafee2

SD1too · 3rd October 2018, 07:37

Ian; read under ‘Modes of Operation’ here for an explanation!

Simon

MSS · 3rd October 2018, 08:41

It is best not to think of this as testing a transformer.

A switched mode PSU should be tested with some load as otherwise the switching elements can misbehave depending on the design.

Put a small load on the output, say a 5W 1k ohm resistor, and test the output.

The output of a 48V DC supply should be close to 48V DC.

Groundsman Willie · 3rd October 2018, 12:46

Damn you all with your helpful answers. I was going to suggest hitting the transformer and seeing whether it changed into a car, boat or plane

2nd October 2018, 16:31	#1
macafee2 This is my second home Rover 75 Saloon & Tourer Join Date: Sep 2012 Location: Lincoln Posts: 14,929 Thanks: 1,630 Thanked 3,032 Times in 2,181 Posts	Advice on testing a trasnformer just back from holiday and found my cctv has gone wrong. I need some advice on testing a transformer/power supply. The label on the back calls it a switching adaptor. model FJ-SW4802000F 240v input. The output should be 48v DC, 2000mA. should I get a fixed AC voltage reading? I think not but I do. thank you macafee2

2nd October 2018, 16:38	#2
kaiser This is my second home 75 Tourer 2.5 Auto, 1.8T, 75V8ZT Join Date: Jun 2007 Location: Johannesburg ZA Posts: 6,200 Thanks: 1 Thanked 859 Times in 613 Posts	I would expect what it says on the box. 48V DC. A bit above or a bit below would not surprise me. If AC maybe a blown diode or rectifier. But what did you measure? __________________ Worth his V8 in gold

3rd October 2018, 07:37	#4
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,382 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	Ian; read under ‘Modes of Operation’ here for an explanation! Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.

3rd October 2018, 08:41	#5
MSS This is my second home Rover 75CDT, Jaguar XF-S 3.0V6, V'xhall Omega V6 Estate, Twintop 1.8VVT, Astra Estate and Corsa 1.2 Join Date: Dec 2007 Location: Suffolk Posts: 7,085 Thanks: 283 Thanked 624 Times in 440 Posts	It is best not to think of this as testing a transformer. A switched mode PSU should be tested with some load as otherwise the switching elements can misbehave depending on the design. Put a small load on the output, say a 5W 1k ohm resistor, and test the output. The output of a 48V DC supply should be close to 48V DC. Last edited by MSS; 3rd October 2018 at 10:09..

3rd October 2018, 12:46	#6
Groundsman Willie Gets stuck in Rover 75 1.8t Join Date: Dec 2017 Location: Newbury Posts: 842 Thanks: 783 Thanked 423 Times in 264 Posts	Damn you all with your helpful answers. I was going to suggest hitting the transformer and seeing whether it changed into a car, boat or plane __________________ Dave