DAB Radio Help!

[Sauron]

Hello Everyone and salutations from the UK!

I got interested in electronics a few months ago and thought I would have a go at fixing my Roberts SolarDAB (V1) radio which was not powering up properly. When plugged in to mains through and adapter I press the power button (It's a soft start button) the screen flashes up with the battery symbol and the speaker makes a 'pop' before turning off again. On the battery it is a similar story, the screen flashes up with the battery symbol but also illuminates before popping and turning off again although this happens less often, but still quite frequently. Playing with the switch a bit and holding it down will eventually turn it on normally though . I thought that the power switch might be a membrane switch and a piece of dirt might have lodged itself between the contacts but it turned out to be just a normal momentary switch. I have noticed that there are two diodes on the power supply board that are getting quite warm, not sure if that is normal though. I have also checked the power supply voltage, all normal (9.5V) I think in the mean time I might try replacing the switch and see if it was just a faulty one. If I were more confident I would do more probing around with a multimeter or oscilloscope but don't want to fry anything.

Sorry I don't know much about the problem, but if you have any  general troubleshooting tips please let me know as well as any ideas on what the problem might be.

Many thanks in advance,
Max

[German_EE]

First rule, look around, especially for suspect solder joints and bulging capacitors

Second rule, check voltages. Look at some of the chips on the PCB and then download a datasheet to see what the supply should be. An example, on a 3,3V chip 3.2V will probably be OK but 2,5V may not be.

Now with those datasheets check the power on reset(s) (a recent video of Dave's on the door intercom may help here). Try powering up the radio without the display backlight connected just in case this is causing a problem.

[Hydrawerk]

Please post a picture of your radio. Is it this?

[Sauron]

No, I believe mine is the first version, I also had a brief look for schematics and things like that, seems like no-one has any...
And thanks for the tips German_EE! I have made progress, I decided to do some testing, turns out on battery it works every time (Tested 100 times(!)). I tried a different power supply and that made no difference and I also tried a identical switch, still made no difference plugged in. I'll begin probing around the board now.

[Hydrawerk]

It looks like it was made in cooperation with Sangean. Some Roberts radios even look like current Sangean models.