Radio cutting out
08-21-2008, 07:20 PM
#1
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Radio cutting out
1990 S4 Auto
I have just completed the instal of a porsche CDR220. Above about half volume (lower with full bass) the display backlighting starts to flash. Any more & the unit cuts out completly. The radio I replaced did similar on occaision!
Most speakers are stock - rear mains were replaced by PO with infinity's. No amp.
Is this likely to be a power supply problem to the radio or a problem with the speakers?
I thought about useing a relay powered off the current switched supply to provide a direct feed to the radio if it was a supply issue.
I have used the stock earth (brown) wire to MPV (all MP's tightened reguarly). Would it pay to run another earth as well in case this is the problem?
Thanks,
Myles
I have just completed the instal of a porsche CDR220. Above about half volume (lower with full bass) the display backlighting starts to flash. Any more & the unit cuts out completly. The radio I replaced did similar on occaision!
Most speakers are stock - rear mains were replaced by PO with infinity's. No amp.
Is this likely to be a power supply problem to the radio or a problem with the speakers?
I thought about useing a relay powered off the current switched supply to provide a direct feed to the radio if it was a supply issue.
I have used the stock earth (brown) wire to MPV (all MP's tightened reguarly). Would it pay to run another earth as well in case this is the problem?
Thanks,
Myles
08-21-2008, 08:08 PM
#2
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Well it sounds like a power supply problem more than a speaker one - unless you are running into speakers at lower impedance than the head-unit can handle.
Why not simply provie a clean supply (Power & Ground) temporarily to see if that solves the problem. If it does swap back to the original ground and see if that still solves it - in which case it is the positive supply.
If that is the case you will need to evaluate where it comes from? and or change it.
the stock connection is direct from the ignition switch (R terminal) to the inductor/suppressor in the console and from there to the radio. However with aftermarket changeovers the supply could be from anywhere...?
If the radio is a very high power output version - it could be too much for the inductor...? though I doubt this is the problem.
Alan
Why not simply provie a clean supply (Power & Ground) temporarily to see if that solves the problem. If it does swap back to the original ground and see if that still solves it - in which case it is the positive supply.
If that is the case you will need to evaluate where it comes from? and or change it.
the stock connection is direct from the ignition switch (R terminal) to the inductor/suppressor in the console and from there to the radio. However with aftermarket changeovers the supply could be from anywhere...?
If the radio is a very high power output version - it could be too much for the inductor...? though I doubt this is the problem.
Alan
08-22-2008, 08:54 AM
#3
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Try running a ground wire directly to the battery. Ground wire should also supply any amps. Power should be picked up at a fuse, after the fuse box. (fuse box acts like a filter for electrical noises)
08-22-2008, 10:48 AM
#4
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Actually the fuse box is not a great source due to switching noise - a direct supply from the battery is actually best via a suppressor - ideally a large value capacitor in parallel with the battery and a series inductor to the head unit - inductors on both supplies if it has switched and unswitched supplies. The switched supply can be accomplished using a relay switched by an ignition or accessory input. The inductors outputs should also be protected by spike suppressors (zener diode + resistor)
On a 928 the fuse box supply has a particularly poor feed. It also series feeds the dashboard and ignition switch - which makes even the stock configuration a rather poor design. The need for the supressor is rooted here as a band aid...
Note that in the stock configuration - there is no fuse (exept on the radio itself) - a particularly stupid idea for this circuit - given it will be messed with by morons...
Although the thinking here may have been that the fuse doesn't help noise due to its higher resistance...
However routing a clean supply from the battery to avoid all this is also challenging due to its location.
Alan
On a 928 the fuse box supply has a particularly poor feed. It also series feeds the dashboard and ignition switch - which makes even the stock configuration a rather poor design. The need for the supressor is rooted here as a band aid...
Note that in the stock configuration - there is no fuse (exept on the radio itself) - a particularly stupid idea for this circuit - given it will be messed with by morons...
Although the thinking here may have been that the fuse doesn't help noise due to its higher resistance...
However routing a clean supply from the battery to avoid all this is also challenging due to its location.
Alan
08-22-2008, 04:43 PM
#5
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Alan.
ran seperate supply from hot terminal under bonnet & from earth point - made little difference. My radio wiring has a fuse on the permanent supply, a fuse on the switched supply (inside a black box holding what looks like a coil) and a fuse on the antenna supply.
The wiring for the box on the switched supply is a thick yellow with black flecks wire. The wiring for the fuse on the permanent supply is red with black flecks. From somewhere I understood that these were 'factory' wire colours.
Since I am running mostly the original speakers (from memory 4ohm or less) and the CDR220 is expecting 4ohm or more, I think that this may be the issue.
I also note that the expected antenna resistance (on the radio specs) is 50 ohm. Factory is less than 4 (specs & measured). Any idea if this would be a problem?
Many thanks,
Myles
ran seperate supply from hot terminal under bonnet & from earth point - made little difference. My radio wiring has a fuse on the permanent supply, a fuse on the switched supply (inside a black box holding what looks like a coil) and a fuse on the antenna supply.
The wiring for the box on the switched supply is a thick yellow with black flecks wire. The wiring for the fuse on the permanent supply is red with black flecks. From somewhere I understood that these were 'factory' wire colours.
Since I am running mostly the original speakers (from memory 4ohm or less) and the CDR220 is expecting 4ohm or more, I think that this may be the issue.
I also note that the expected antenna resistance (on the radio specs) is 50 ohm. Factory is less than 4 (specs & measured). Any idea if this would be a problem?
Many thanks,
Myles
08-22-2008, 04:55 PM
#6
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I don't think the antenna is causing the issue - sounds like its the speaker impedance... Check the antenna for reception once you get the basic operation fixed. You will be measuring the ouput of the antenna amp not the antenna itself...
Whilst I noted the best connection method for low noise - it should not be needed for a regular install - the factory set-up should work OK (especially with an extra indictor for the non-switched supply which it sounds like you have).
Only if you are going to super hi-fi and high power amplification (>500W) would I recommend you consider this path...
I do have such a system (custom built) and it was a real pain to install and hide...
BTW the colors you mentioned do not sound like stock. Stock wiring uses a singe contrasting color tracer line only - no flecking or multi colored tracer lines.
Alan
Whilst I noted the best connection method for low noise - it should not be needed for a regular install - the factory set-up should work OK (especially with an extra indictor for the non-switched supply which it sounds like you have).
Only if you are going to super hi-fi and high power amplification (>500W) would I recommend you consider this path...
I do have such a system (custom built) and it was a real pain to install and hide...
BTW the colors you mentioned do not sound like stock. Stock wiring uses a singe contrasting color tracer line only - no flecking or multi colored tracer lines.
Alan