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Did I fry my CustomAutosound USA-66?
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fatfenders
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Dec 8, 2012, 1:14 AM
Post #1 of 12
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Did I fry my CustomAutosound USA-66?
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1936 Chevrolet Coupe (Street Rod)
Completed 2006. Been on the road as a daily driver ever since.
Originally installed a CustomAutosound USA-3 but in such a way that I controlled it with the original 1936 radio head. I chose the USA-3 (and more recently the USA-66) because they have a manual tuner that will stay synch'd with the '36 head dial).
I recently decided to upgrade to the USA-66 because I want to (1) have Bluetooth capability (AUX in) and I want to put an amp behind it (RCA out ports). I am currently part of the way through that process. Because I want to hide the radio and keep the dash looking as stock as possible, I have attempted to 'remote' (1) AM/FM selector (2) AUX - CD - Radio selector (3) a RGB (4 pin) LED that indicates 'source'. The terminal strip mounted on the front is for that purpose.
1 -2 toggle input (AUX - CD - Radio)
3 - 5 Am /FM SPDT switch
6 - 9 4 pin RGB LED
Fired it up for the first time yesterday. Here is what happened:
Only the left speakers, both front and rear, worked.
The LED never lit up
I was able to successfully toggle (remotely) through AUX - CD - Radio
Then I really screwed up. As I began shutting down for the night I momentarily, accidentally shorted the (1) IGN and (2) BATT wires (temp connected to an alligator clip) against ground. Blew the fuse in the "filter/fuse" box. Replaced the fuse. Now nothing works. I do get an electronic 'snap' when I turn the radio on.
What I don't understand (among many things) is why the fuse blew. The circuit is BATT - Alligator clip - temp connected IGN/BATT wires - Fuse - radio. How did the fuse blow when it is down stream from where the momentary short I caused is?
While I have the two aforementioned problems, obviously they are not an issue until I can get the radio working again.
As you can probably tell, I know my way around cars but I am a real lightweight when it comes to actual radio technology. That said, I would like to make a good honest attempt at fixing whatever I broke. Call it a 'winter project!"
(This post was edited by fatfenders on Dec 8, 2012, 1:16 AM)
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Discretesignals
Ultimate Carjunky
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Dec 8, 2012, 11:16 AM
Post #2 of 12
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Re: Did I fry my CustomAutosound USA-66?
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That is one heck of an unusual set up.
The fuse blew because a circuit was created that caused the current to flow directly to ground instead of through the radio's electronics. The amount of current exceeded the rating of the fuse which caused the fuse element to melt. Why the radio doesn't operate after restoring power is unknown without testing. Since you have in out of the vehicle, you could bench test the radio by itself by connecting it to an auxilary source of power and external speakers. If the radio still doesn't operate, you'll need to see an electronics repair technician. If it does operate, you have wiring problems inside the vehicle.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 8, 2012, 11:17 AM)
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Sidom
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Dec 8, 2012, 11:31 AM
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Re: Did I fry my CustomAutosound USA-66?
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Well I am not an electrical expert by any means but if I understand you post correctly to get the am/fm or aux to work you are running 12v (either via batt or ign) or #1 or #2 which ever one you want to work.
The amperage draw thru any circuit is determinded by the resistance of the load & total resistance for the whole circuit. Basically on a 12v circuit if the load (light, motor, radio inputs, anything) has 6 ohms of resistance, the most current flow that circuit could have would be 2 amps.....and all is good.
when your power clips hit ground, you created what is called a short circuit. You have a power source, ground but no load to limit current flow (amps) so you are going to get maximum current flow, this is the reason for fuses, to protect a circuit from too much current.
From what you posted, in the short amount of time it took for the fuse to blow, was enough time to damge the unit.....I would may take apart the unit to see if there is an other fuses that might of blown but it doesn't look good...
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fatfenders
New User
Dec 8, 2012, 12:01 PM
Post #4 of 12
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Re: Did I fry my CustomAutosound USA-66?
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Thank you you both for your replies but just to make sure we are all on the same page I am a self professed lightweight about radios specifically, not automotive electronics (or electronics) in general. As an example, I stuffed a lot of electronics into my street rod. Below is part of the "Retained Accessory Control" I designed/installed using my own stuff and parts from the donor car, a '95 Pontiac'. What I am looking for is advice on what might be some obvious things to check given my 'screw-up".
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fatfenders
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Dec 8, 2012, 12:21 PM
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Re: Did I fry my CustomAutosound USA-66?
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To clarify why I am confused as to why the fuse blew, refer to the simple diagram below, with the red line representing the inadvertent short I caused... Why would the fuse blow?
(This post was edited by fatfenders on Dec 8, 2012, 2:05 PM)
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Discretesignals
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Dec 8, 2012, 12:44 PM
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Re: Did I fry my CustomAutosound USA-66?
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Well, in that diagram the fuse shouldn't have blown, but the wiring and insulation would have melted and you would have seen smoke. Something would have to be shorted in the radio's circuitry or on the power side of the circuit after the fuse before it it connects to the radio to cause the fuse to pop in that diagram.
If you have power at the batt and hot when ignition is on or RAC relay is energized along with a good ground at the radio, make sure you don't have any speaker channels with shorts. If you have power and grounds at your radio and no shorted channels, something is bad inside the radio.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 8, 2012, 12:50 PM)
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Sidom
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Dec 8, 2012, 12:45 PM
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Re: Did I fry my CustomAutosound USA-66?
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I'm sure an electrical engineer could give an answer with all the I's dotted & T's crossed but I'll just give you the field answer I know to be true.....mainly from being there & done that...
I can see by your diagram that going by the fact the electricity will take the shortest path to ground you would think that the "surge" would just take the shortest path back to ground bypassing the rest of the circuit....
It doesn't work like that, the whole circuit takes the hit.....everything that is wired into that path.
It is the same principle as if your positive battery cable gets up against the exhaust manifold (right next to where the negative cable is bolt to the block for ground) and shorts out. All the max fuses get popped in the fuse boxes and in worst cases a lot of modules & other electronics gets damaged.... The current doesn't just go back to the battery ruining the cables & battery, it takes everything else with it...
(This post was edited by Sidom on Dec 8, 2012, 12:46 PM)
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Discretesignals
Ultimate Carjunky
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Dec 8, 2012, 1:01 PM
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Re: Did I fry my CustomAutosound USA-66?
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This is an interesting subject.
So, if I lay a wrench across the battery terminals it will take out modules that are operating that are using the battery as a power source? Would think that since the current has found a place that is alot easier to go through to get to the other side of the battery, that those items would be lacking the current they need to operate.
Now if the engine is running and the electrical system is using the alternator as a power source and the battery is acting as buffer and you lay a wrench across the battery terminals, the alternator is going to blow some diodes. For a split second you might see a huge voltage spike before the alternator blows which could take out a module, but the source at the modules is still being pulled low by the wrench.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 8, 2012, 1:02 PM)
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Discretesignals
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Dec 8, 2012, 1:11 PM
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Re: Did I fry my CustomAutosound USA-66?
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Maybe some type of inductive kick occured in the radio, kind of like one that is made by a coil of wire once it's magnetic field collapses that was brought on by the short once it was removed. The voltage generated by the inductive kick blew something out in the radio that caused other solid state components in the radio to see too much current. They short and blow the fuse?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 8, 2012, 1:39 PM)
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Sidom
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Dec 8, 2012, 1:16 PM
Post #10 of 12
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Re: Did I fry my CustomAutosound USA-66?
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That's the fun stuff about this biz & stuff that will make you pull your hair out some times...
The wrench scenairo is a bit different.....That would be a completely seperate circuit since it's ground path doesn't require it to use the negative cable as a ground. Sparks would fly whether the battery was wired up in the car or just sitting on the ground.
But I believe you are correct that creating a surge like that with the car running would do some damage to other systems.....
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Discretesignals
Ultimate Carjunky
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Dec 8, 2012, 1:28 PM
Post #11 of 12
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Re: Did I fry my CustomAutosound USA-66?
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Heck we could experiment on a customer's car. Hook a scope up to a power and ground circuit at a specific module...put attenuators on and watch to see what happens when shorts are induced. Set the scope to record and we can induce shorts in different parts of unfused circuits with our welding helmets and gloves on...LOL..
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Sidom
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Dec 8, 2012, 2:18 PM
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Re: Did I fry my CustomAutosound USA-66?
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I've got a Z3 sitting in the bay we can try out on Monday......I'll run it by the boss but I really can't forsee any problems with this.....
I know you like experiementing with this stuff & probably are going to.........lol....
If you do, current ramp it... You could actually fabricate a simple circuit to ramp with just wire, 5 amp fuse holder & a load, a bulb would do.
I wouldn't use a low amp probe for the surge though, might damage the probe.......If you divide 12 by .001, thats a pretty good surge....
Now you got me curious to what kind of spike you would see on the ground side.....
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