Electrical issues and sound system

[Phil Brooks]

We’ve got a Bessacarr E510 fitted with a Blaupunkt London MP48 radio .
Over the last couple of years we’ve had an intermittent problem......we were hearing what sounded like a bunch of voracious rats partying above our heads! The cracking and banging, we eventually found was emanating from the speakers set into the inner roof skin. Condensation may have been causing a short in the speakers....
I got the roof resealed and the problem subsided. The very loud noise is back....even after isolating and removing every fuse I could find that might be linked to the sound system I could only stop it by disconnecting both the engine and leisure batteries. The issue only disappeared when the radio was playing.
Could it be a fault with the radio or aerial?
Maybe it’s an earthing issue.......but how can I find out?
Could some sneaky electrical component I don’t know about be transmitting so that that speakers pick it up ?
I would be eternally grateful if a solution is out there.....I can’t leave the van connected to power in any way.......the banging can be heard over 20 metres away inside the house !!
Thank you Phil

 

[Dustydog]

Phil,
Is it a motor home? You refer to engine batteries?
Did you change the loudspeakers? Or are they nothing to do with this noise? 20 metres and you can hear it is weird?? We have a sister forum , Practical Motorhome.

 

[Beachball]

Just look up a Bessacar E510 it a Motorhome you need to be on the other forum like (Dusty) said they might be able to answer your questions .

 

[Woodentop]

Two things spring to mind.:
Firstly make sure the removable front panel is securely fitted and that contacts on the base and on the panel are clean and not fluffed up.
Secondly, make sure the earth to the radio is sound - specifically the connectors on the back are pushed fully home and the blades that make the actual contact are also fully home. If the radio is picking up its earth through an aerial connection then cable flexing can cause problems.
The other possibility is that the radio is at fault. It uses a 'soft' power switch which means the radio has power on it at all times so the power control (switch) could be leaking power to the audio amp section and as there is nothing driving the amps they can make a frying noise. Suggest that next time it occurs pop the front panel off without turning the radio on or off from its current state. If the fault stays then it is the radio, if it goes away then you need to look elsewhere.
Oh, and condensation on the speaker terminals will make no difference whatsoever - the resistances in that circuit are very very low. You need high resistance (technically impedance) before moisture will affect it.

 

[ProfJohnL]

Obviously I cannot witness the problem, but if the sound is so loud that it can be heard 20M away and its independent on eth radio's volume setting, then it suggests to me its a radio power connection problem or it might be the radio it's self.

To help identify what might be the problem, most car radios can be withdrawn from their location. The wires are usually connected with a dedicated plug on the back, so it should be easy to disconnect the radio. If that stops the noise then it points to the radio.

Whilst the radio is out, it would be worth checking the multiple wires and their connectors in the multipole plug.

Even though we are only looking at 12V circuits, if you are not confident with electrics it would be safest to refer the problem to an expert.

 

[Tintentman]

Interference on a radio can be a swine to sort and can come from a multitude of sources. By what you have described it appears the power supply is ok connection wise but it could be interference on that 12 volt supply or interference picked up by the aerial or its cable to set .
In a previous caravan I installed my own roof solar panel and MPPT controller.which worked great but I suffered noticeable interference on listening to any FM station. Worse in stereo than if switched to mono. Squeaks and general background frying type noises
A lot of investigation later after isolating things I found it was the solar MPPT controller producing rf ( radio frequency) interference which it kindly passed onto its input wiring from the roof solar panel.
The solar panel then acted as an transmitter aerial in itself and sitting close to the radio aerial , radio reception didn’t stand a chance.

I contacted the solar panel/ MPPT controller supplier who said he would escalate the issue to the manufacturers in China. I never heard what transpired but from my days dabbling in electronics - I would guess a rf choke in each of the input connections from the solar panel would possibly help?

So if anyone is getting interference on their radios try disconnecting your solar panel, if they have one fitted, to see what’s what.
if your caravans radio is a DAB version then any RF interference shouldn’t affect the radio.
Good luck

 

[DMM]

I have a Swift RS590 Motorhome which has a Blaupunkt London MP48 radio. Over the past 2 weeks I have also been experiencing noises sounding like trapped animals behind the dashboard. The noise could be heard by our next door neighbour some 20 mtrs away and is now waking us up at night. Trying to dismantle the dashboard to "rescue" the animal or animals, the noise started again and seemed to be coming from the door. The penny dropped and I could hear the banging and scratching noises coming from the speakers. Going onto the internet and searching on this phenomenon I discovered a raft of people having identical problems with Swift Motorhomes and this radio. Following through the forum string someone installed an entry back in September this year, which sated that their Blaupunkt London MP48 has been periodically generating this noise over the past 3 years even though the radio is off and the sound switched down before turning off. Seemingly through investigating the cause he looked through the radio menu and found a setting "High Sensitivity". He recommends turning the value to either nill or 1 and the noise for him, has gone away. I have tried this and I still get the noise intermittently. I'm now trying to contact Blaupunkt to see if they have guidance. I will update on any response I receive.

 

[DMM]

I found a UK Customer Service contact for Blaupukt 'sales@autosound.co.uk' and informed them of this issue and the numerous forums of members and individuals suffering this issue. I asked about the High Sensitivity and if any other source could be impacting and interfering with the speaker infrastructure apart from the radio. They have not addressed any of these specifics and have responded with the below;
"We’ve no idea – we’ve never seen the problem before – as I think the MP48 radio was produced in 1998 and is probably 20+ years old I’d swop the radio and see if this solved the issue. (Although we’re not certain if it will ..)"

I continue my investigations.

 

[DMM]

I found a Blaupunkt London MP48 radio user guide online and reading through it I note that there is a Telephone connection capability which can override the radio volume and "Manage the speakers". I have assumed this is the problematic interface and have gone through the radio menu until finding Tel Vol and have switched this to zero as I do not use this interface. Since applying this earlier today all is peace and quiet. The oncoming of my issue started at the end of November when my neighbourhood started turning on Christmas lights so again I'm assuming the Telephone management in the Radio is picking up some sort of frequency from the various electrical devices and generating the noise.