Hatteland monitor power supply

[2PAC Mafia]

Hi,

I now what I´m going to explain sounds very strange but it´s happening...

I have to repair a Hatteland monitor which I saw it had a problem at it´s DC/DC converter. It used a DC/DC:

Hercules 6 MAH 36 006, Input: 9-36V, Output: 12V

Datasheet: https://www.powerbox.com.au/media/specification_sheet/MAH 36.pdf

This was damaged. I removed it and I connect my power supply to 12V, the consumption was 0,7A and the monitor worked perfectly.

Then I bought a Datel UHE-12/2500-Q12-C to replace the original DC/DC.

Datasheet: https://power.murata.com/data/power/uhe12-30w.pdf

When I installed it I saw how monitor didn´t switch on and I heard a click-click-click... from the DC/DC. I had 12V output but monitor didn´t switch on. I connected the DC/DC to a bulb and I saw the bulb like on-off-on-off all the time so I supposed the DC/DC came to me already defective.

I bought a second one, this time a DC/DC Traco power TEN 30-2412WIN.

Datasheet: **broken link removed**

When I installed I had exactly the same behavieur, this time I didn´t leave connected more than a few seconds to avoid damage it. I connected a 12V 21W at its output and it worked supplying 24V at input 1A consumption.

If I connect 12V at the PCB output, where the DC/DC should be, everything works, monitor switch on. I also tested the filtering input at PCB, I get the 24V input at pins where DC/DC should be.

For some reason, the behavieur is like there is too much consumption when I connect the DC/DC, then it starts protecting itself, but it has no sense because I already tested the consumption is only 0,7A and DC/DC output supports up to 2,5A!!!

No idea what is happening on this stupid issue...

 

[tomizett]

It's got to be something todo with inrush current... You say that both replacement DC/DC converters switch on and off rapidly when the monitor is connected?
You could start by connecting a large capacitor in parallel with the converter output - first check that the converter will start and run with only the capacitor connected, and then try starting it with the capacitor and the monitor connected. You could also try a small resistor directly at the output of the converter (before the capacitor) to limit the inrush, but of course this cannot be so big that you get a significant voltage drop across it under load.

Often converters/PSUs that appear equal on paper behave quite differently under overload.

 

[tunedwolf]

More likely, I think anyway, is that the monitor starts off in standby mode and is drawing too little current for the converter to regulate properly, thus it goes into foldback protection before you have even switched the monitor on. Put a lamp across the output of the converter, in parallel with your monitor, and see how you get on

 

[2PAC Mafia]

Hi Tomizett,

It's got to be something todo with inrush current... You say that both replacement DC/DC converters switch on and off rapidly when the monitor is connected?
You could start by connecting a large capacitor in parallel with the converter output - first check that the converter will start and run with only the capacitor connected, and then try starting it with the capacitor and the monitor connected. You could also try a small resistor directly at the output of the converter (before the capacitor) to limit the inrush, but of course this cannot be so big that you get a significant voltage drop across it under load.

Often converters/PSUs that appear equal on paper behave quite differently under overload.

You were completely right, I put a 2200uF 25V capacitor and it works correctly. It was so fast that I couldn´t see this overcurrent peak. Thank you very much for your help.

More likely, I think anyway, is that the monitor starts off in standby mode and is drawing too little current for the converter to regulate properly, thus it goes into foldback protection before you have even switched the monitor on. Put a lamp across the output of the converter, in parallel with your monitor, and see how you get on

I also tested, but it was overcurrent so this didn´t work to solve the problem.

 

[tomizett]

Glad to hear it!