Problem with TomTom Go 300 Speaker - Help?

[thompsdw]

I recently took my Go 300 on a business trip and left it in the car most of the day. I left it on the mount. When I came out to the car the unit worked fine until the battery went dead. When I plugged the unit back in, the external speaker began to make a loud buzzing noise. If I powered the unit down and then back up the noise continued. The unit would otherwise route normally. The sound continued even with the speaker turned off. I setup a RMA because I have 10 days (can you believe this one) of warranty left. Left the unit off all night and charging.

Next day, turned it on and it made the same annoying noise. Turned it off and back on one more time - no noise. Used the unit for the past 2 days and the problem appears to have disappeared. The only thing I did to repair it was let it sit and I did upgrade the firmware. I have a hard time thinking this was a software failure, but at this point I am concerned that if I send it in I will simply get it back saying "we found nothing wrong". Has anyone had any similar failures, I am not sure what to do at this point. I have nothing to loose but postage from sending it in - I guess.

[vroomfondel]

1. could the unit have been hot for some time while left in the car?
2. did you start the car with the TT connected?

[thompsdw]

1. could the unit have been hot for some time while left in the car? Yes

2. did you start the car with the TT connected? Yes, but I do not belive the power was turned on.

[vroomfondel]

I'm wondering if the electronics in the unit or power-adaptor were damaged by the heat or switchon.

Buzzing sounds like badly filtered power supply.
As an electonic engineer by training I'd first look at the car supply gadget.
This could be eliminated by substitition.

Whats the unit sound like when its on a house supply?

[thompsdw]

It did it on either the house charger or the car charger. What is amazing is that it simply stopped.

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