Dual NR 5 DAB Radio. Leak on circuit/power board...

[Shotty]

Hi all,

I am having a real issue with a German ‘Dual’ branded DAB radio that has a leak on the board where power cable would plug in. I was told that the wrong power cable (wattage) was plugged in and that it “blew”. As this is a valuable radio, I would like to try and repair it instead of just throwing it away.

There is a dark brown liquid on one part of the board and it also looks like it has bubbled up. This works with a European 2 pin plug but I have also tried with a UK 3 pin one but to no avail. I cannot work out if the leak came from one of the two nearby capacitors or perhaps a plain metal box next to where the leak was. I have some spare capacitors in case and want to buy some alchohol and cotton wool buds to clean it with but hoped someone here might be able to assist (as cheeky as I am for asking) before I try.

I would be very greatful if someone might be able to help.





Thanks


Scott

 

[kellys_eye]

Show the reverse of the board and tell us the make/model etc.

 

[Shotty]

Hi Kellys_eyes,

Thank you for your reply. I have managed to get a photo of the back of the board but I couldn’t find a model number. I did try some of the numbers (in variations as suggested in sticky post) but not sure if there is one. I will send another photo of something which looks like a model number.



I’m just gonna remove the back again now and will post it shortly.

Thanks

Scott

 

[Shotty]

It has this on top side of board but not sure if it is the model number. Google results didn’t find anything either.



It also has ‘R29’ after the circled ‘R’

Thanks

Scott

 

[kellys_eye]

How about a picture of the whole equipment? The make/model is more likely to be on the casing than on the pcb. And if it's not then someone on here may just recognise the equipment from experience....

 

[Shotty]

Oh, the model number of the actual radio I put in the title. It’s a Dual NR 5 DAB.




Thanks

Scott

 

[kellys_eye]

Hmmmm - the gungy stuff reminds me of the type of gluey stuff they use to hold stuff that's sensitive to vibration - potentially hidden under the metal can-type enclose nearby. It certainly doesn't look like residue from any blown component that I've ever seen 'blown'....

The picture I've attached shows the rear of the power input socket - there looks to be a reverse polarity protection diode beside it (could be a surge suppressor too).

Did you check that the power pack you're using has a 12V output? With 12V positive on the centre pin? and is capable of delivering 2A? Has the correct sized barrel connector? The type of mains lead is irrelevant. If the 12V is present we can discount the power pack as a problem.

We'd need to see some brighter lit close-ups of the PCB around the rear of the power socket so we can trace the tracks to the input power regulator(s) if the above checks prove to be ok.

 

[davenn]

There is a dark brown liquid on one part of the board and it also looks like it has bubbled up.

Hmmmm - the gungy stuff reminds me of the type of gluey stuff they use to hold stuff that's sensitive to vibration - potentially hidden under the metal can-type enclose nearby. It certainly doesn't look like residue from any blown component that I've ever seen 'blown'....

yes exactly



let me make this very clear .... IT IS NOT A LEAK ... It is supposed to be there for circuit stability of the oscillator section

Dave

 

[Shotty]

Ok, great. Thanks for the update. I thought it must have been a fuse/power adapter problem but I tried the original German power plug with UK converter and a UK power adapter but neither worked. I will try and Test a little more. All I know is that I plug a working power cable into the radio and no display or power to it but it works fine in a different device.

I’m glad you have confirmed that the gungy stuff is normal. Now I can look into what else it could be. All I was told by the person I got it from
Is that she had plugged a cable with incorrect voltage into it.

Thanks

Scott

 

[kellys_eye]

Check the diode in this picture first: D1, above the inductor.

 

[Shotty]

Hi kellys_eye,

Thank you for your help so far. I managed to get my multimeter on both sides of the diode and I do not get a reading in either direction. Does that mean it’s bad. From what I have read, the diode should allow current but only in one direction.

Do I need to unsolder and test again or should I just try and swap it out for a new one?

Also, it looks like it says 140GW. Would you know which one I need to buy to replace it?

Thanks

Scott

 

[kellys_eye]

What range did you use the multimeter on?

 

[Shotty]

I’m not sure about range. I just set it to diode setting and then done it on that. Two other diodes on the board returned values in a single direction but the one you mentioned did not show a current in either direction.

Thanks

 

[kellys_eye]

When you meter a diode it will show as a DC voltage (0.3 to 0.9V - approx - one way, zero volts the other) - if it is showing 0V both directions then, yes, it is probably open-circuit.

I'd need a closer look at the board traces to determine if it is as suspected. Some diodes are fitted in series (to prevent polarity reversal) and some in parallel (does the same thing but tends to 'blow' the diode if powered incorrectly.

Other types of diode are fitted to protect against over voltage - so there is more than one potential cause for failure which itself may have transferred further through the system to other devices... such as a voltage regulator. Without a clear picture of the tracks and components it isn't possible to trace the route of the applied voltage to see where further, potential, faults may lie.