S2 radio, Aux in ?

[Henry]

For some time now I've been toying with the thought of adding an 'aux input' to this radio (the Clarion S2 mode-PU1562A) by means of modifying the cassette input-don't really use cassettes now.
Upon dismantling a spare radio, I was really pleased to see that the cassette mechanism came out as a cartridge type with inputs clearly marked on one of the pcb's.
Today with Paul (CitroenXM) we set about trying to achieve this( rained off from other things!). Set up on the dining table we soldered a lead with a 3.5mm on the end to 2 points on the aforementioned pcb, marked I/P left and right and obviously a ground too! realising that we were in effect piggybacking onto the cassette head outputs-and that the cassette option will only be selected with a tape in situ, we decided to use a blank tape-and Voila! 3.5mm plugged into MP3 player and music-clear and interference free!
However, joy was short lived when we installed it into Pauls car and tried it with engine running-there was interference that seemed to be changing with the revs-alternator noise maybe? If so suppression is required-and at what level and where?
Anyone on here with 'the knowledge'?

many thanks,
Alan.

This post has been edited by Henry on April 29, 2012 07:00 pm

[Norman]

Hi Henry/Paul,
Re the interferance i had asimilar problem when i installed a CB radio into the xm loads of interferance as the engine speed increased also not very noticable on the broadcast radio but there in the background, i called in a autoelectrician and he found that previously some one had installed a dual charging system probely for a now none existance towing bar and had just cu the cables off at the rear, so he disconnected the second cherging circuit from the altenator and silence reined no more interferance.

Hope this helps,

Norman,

Ps the screened input cable to the radio must be earthed on the pcb board next to the inputs if the inputs cables have too much exposed length the will act as a antenna and pickup interferance.

[Henry]

Thanks Norman-it has since been reported back to me from Paul that the culprit was....his USB phone charger and that tonight it was clear and interference free!
The input ground is short and soldered to the chassis too.

Thanks again,
Alan.