RetroSound Troubleshooting: No, or poor playback when the engine is running: Tip 3

Radios in which devices played through a USB port cut out while vehicle is running:

There are five main issues that cause this problem:

• Poor ground or shared ground with other electronics. Move the ground to a clean location or ground the radio directly to the negative battery terminal.
• Ignition voltage is erratic. Test to make certain both power sources are good.  Make sure both the RED ignition and the YELLOW constant do not have spikes or drops in voltage.  The radio needs constant voltage of between 11 and 14.9 volts. 
  
  
• USB cable routed near or over ignition or high current wiring. Make sure the USB cable(s) are not wrapped up with the ignition harness and are routed away from the vehicle’s ignition switch.
  
  
• Old vehicle wiring. Remember that, in most cases, we are dealing with vehicles that are over forty years old, with forty year-old electrical systems.  Older ignitions -- such as Lucas wiring -- and many other older vehicles simply need updated plugs, wires and caps installed. 
  
  
• RF interference caused by HEI or MSD after-market ignition systems.
  1. MSD: make sure main control box is isolated from the firewall.  Also make sure it is not sharing the same ground point as the radio.
  2. HEI: if your ignition is too advanced it will cause premature spark, creating RF interference.  Adjust the ignition so that it does not fire prematurely. Some vehicles with HEI ignition need RF shielding on the ignition part.  Another alternative is to put shielding -- such as ferrite coils -- on the radio’s USB cables.

Because our radios feature an external USB cable on a three-foot umbilical, the USB cable itself can act as an antenna for RF interference.  Some vehicles simply either have too much RF interference or other wiring issues to be able to use a unit with external USB inputs.