The Stovebolt Site Forums The Shop Area The Electrical Bay USA-630 Radio - USB Issue

My better half bought me a USA-630 radio for Christmas to install in my '65 C10. Everything worked perfectly until I changed over to an HEI distributor. Now the USB will not work when the truck is cranked (everything else works perfectly). I took the radio out, call the manufacturer and told them the issue. They said to send it back. I did and they could find no issues with the radio or USB adapter. I hooked the radio up at the battery when I received it back and the USB worked perfectly (truck running). I thought GREAT. Well when I installed the radio back in the dash, it would do the same thing as before. With the ignition on, it works great. When I crank the truck...no go on the USB. I am thinking the HEI is interferring some way with the USB...in fact I know that is the case. Do they make any kind of shielding that I may could use the keep the radio circuits shielded from the HEI. The HEI distributor is right against the firewall (close to the radio). There was no problem with the USB with the points distributor. Any suggestions at all are welcome.

"When I crank the truck...no go on the USB." Does that mean the only problem is when you're starting the truck? It works normally after the starter disengages and the truck is running?

The USB will continue to work until you crank the truck. At that point, the display goes to 000000 and the USB stops playing. You can depress the button that changes to radio and the radio works fine but the USB will not work again until you shut the truck off and then switch it on. With just the ignition switched on, it works perfectly again but as soon as you crank it, the same as above. I know it has to be the HEI distributor because with the points distributor it worked perfectly. I was an electronic technician in the Air Force many years ago but have not run into this before. It seems to be a proximity to the HEI problem since wiring it up next to the battery it works fine even with truck running. I also tried wiring the unit with both the ignition input and the battery input hooked to the battery wire (with the unit in the dash) and with that hookup you can play the unit without ignition switched on and the USB works fine. As soon as you crank the truck...USB acts up again.

It sure sounds like the HEI is the culprit. It does work with a magnet and magnets are bad for all things digital. I have no clue as how you could shield it though. Good luck. I'm sure someone here will have a idea or ten.

Thanks for the reply. Maybe someone will have any idea for a fix.

Sounds like you have a RF interference problem. The HEI is producing some sort of high frequency (RF) that is shuting down your system. We old guys remember the "buzz"th that AM radios had back in the day from same sort of problem. Some possible causes and solutions...
1. Did you change you spark plug wires? Make sure they are of type that suppresses RF. They will act like little antennas to the HEI if not.
2. Spark plugs. They also must be the right type.
3. Wiring to you radio. One cheap and nasy way to cut down on induced RF is to twist your power and signal wires. Idea is...when an induced RF pulse hits one wire with, let's say, signal going one way, it induced a reverse pluse in the other wire, thus canceling the pluse.
4. Shielding. This would mean running as much of your wiring as possible in spiral metallic flex tubing and grounding one end of it.
5. Capacitor. As a capacitor blocks DC and "passes" AC, you can hook a cap. up to your power feed to "drain off" the RF. Close to the radio would be best.
That's a start, other might have better ideas. Good luck.

I forgot to add. Keep all wires as short as possible. By this I don't mean to bundle them up with a twist tie. Any unneeded length is an antenna to the RF. Remember, modern cars use all these electronic do-dads and they have HEIs also. I might also look into shielding any wire that is under your dash and goes to your HEI. It just could be transmitting the RF into your dash area.