2820 and earphone "hum"

[Dale]

I have been following this thread and was visiting the Autocom factory today. As soon as I mentioned hum, one of the designers pointed out that the TFT displays do tend to produce it.

Beemerboy,

Did the bright lads at Autocom they say wether or not they had taken it any further? i.e. contacted Garmin or looked to solve the problem thenselves?

I know it's not their problem, but maybe they have given it some thought.

Dale (wishing I knew more about electrickery!)

 

[beemerboy9]

Beemerboy,

Did the bright lads at Autocom they say wether or not they had taken it any further? i.e. contacted Garmin or looked to solve the problem thenselves?

I know it's not their problem, but maybe they have given it some thought.

Dale (wishing I knew more about electrickery!)

I don't think they will take it further.
1) They are doing a lot of new product development on their own gear - hopefully in time for the upcoming big British bike show.
2) They are busy working with BMW/Garmin to allow the Nav III phone facility to interface with Autocom in a simpler manner.
2) I have a sneaking suspicion that they think the mono music output from the 2820 via the multpin connector is good enough for most users. Therefore they will not put extra effort into make the stereo output work and it will mean even more isolation blocks in the cable.
Mono is good enough for me at 70 mph - but YMMV.
3) My 2820 was the first they had seen with 3.1 software installed and the audio jack functionality enabled.

 

[Dale]

Got a reply ...

from Garmin about the "hum" problem (better late than never I suppose).

Seems they are aware of the problem and think they can do a software fix - see extract from mail below.

"I have had some talk [with the US engineers] of this problem and I am lead to believe that there is going to be a software update released to overcome this problem. Unfortunatley I don't have a confirmed lead time on the release of this."

Personally I dont see how it can be software related, but them I am not an electronics expert by any means so let's give them the benefit of the doubt at this stage. Will give them a call later today to discuss.

Dale

 

[araspitfire]

If I had to make an educated guess... (based on your quote)

I'd say that the computer in the 2820 is feeding the backlight a signal. Signals like this often come as a square wave where the on time is directly proportional to the brightness... and when the on time increases, the off time decreases, so your square wave is always the same frequence.. the principle is called PWM (pulse width modulation)

If they change the frequency of the on/off pulse so that it (and it's harmonics) don't cause the interference, then a software fix could indeed solve the problem...

Before your quote, I'd have said they were missing a bit of noise suppression hardware like capacitors and inductors, and maybe appropriate shielding... If the sharp edges of the pulse were rounded a bit with the right hardware, there'd be no problem...

But even so, sounds like there is a hope of at least solving this with a bodge fix.

Al...

 

[alimey4u2]

Mine hums too.... same problem, thanks for the info & the thread.......

 

[Jonny Dub]

has this gone quiet ...

or does the hum still , er, hum?

I've had my 2820 replaced about 4 weeks back (due to some problem causing it not to get past the switch on screen) and have finally got around to plumbing an audio lead to my autocom. Consequently, I'm having the same issue with a humming noise etc as above. I'm curious to see if a fix has been found given that some time has passed since this first appeared.

Cheers

Jonny

 

[Dale]

Mine still hums

I must be honest and say that I am VERY disappointed with Garmins response to this - after following all the regular support channels it seems that nothing is being done. Either they don't consider it a problem or are not interested. In hind sight I should have sent the thing back to the dealer straight away and demanded a refund - too late for that I suppose In any event, I have had enough of trying to get blood out of the stone and have given up (score one to Garmin I suppose). Perhaps one day I will buy a BT headset and "work around" the problem in that way.

On the brighter side, if you are plugging it into a Autocom, I think the problem may be one of "common ground". There were some threads on that a while ago and most folk seem to have reported a successfull result.

Dale