Pioneer F900BT no signal from preamp outputs

[jtaylo82]

My pioneer F900BT has three sets of preamp outputs. One for front, rear, and subwoofer. I have read the posts about the pico fuse problem but I have never hot swapped my rca's ever. I am sure it stopped working when I was riding and listening one day I heard a loud noise that sounded like an ambulance siren coming from my speakers. The unit wasnt even at 50% volume at that time so I turned it completely down but the volume of the noise stayed the same. After the noise went away i smelled a burning smell and later discovered the coils were burnt out in both of my memphis mojo 12's. Just for info purposes they are 4ohm DVC pushed by an orion XTR15001 at 1ohms. I replaced the mojo's with two RF TOD412's but no sound so I troubleshooted the issue from that point. I started with checking AC voltage across the speaker outputs on the Orion amp and came up with 0. I checked the rca leading to the Orion amp for DC voltage and came up with 0. I moved to the head unit and checked the DC voltage at the headunit and the results were 0 on all the preamp outputs. I did a little research online and tried the temporary pico fuse fix in which i grounded the rca shields to the back of the headunit and this still resulted in a negative outcome. The pioneer unit is in my pontiac g6 and is connected to my onstar so the only speakers that play are my front door speakers which I left factory to retain my onstar voice and chimes. I have a Memphis SRX 4.300 amp connected to the rear rca outputs and I am getting no activity from it either. What should I do? I am a newbie but I'm wondering should I open up the F900bt to repair the pico or is it something else since the temporary fix didn't work?

[Chris Hammer]

Try using a RCA to 3.5mm and check your amps with an ipod or phone to see if they are working. Make sure you turn the gain down some and increase it slowly..I did this once and forgot about it and my phone was maxed out =bad stuff lol.

[jtaylo82]

Try using a RCA to 3.5mm and check your amps with an ipod or phone to see if they are working. Make sure you turn the gain down some and increase it slowly..I did this once and forgot about it and my phone was maxed out =bad stuff lol.

Ok I just tried this and I am not getting any output from the Orion but I am getting output from the memphis amplifier. So now it looks like I really have a serious problem.

[jtaylo82]

OK....I have found the problem with the orion amp. I disassembled it and discovered one of the MOSFETS have burnt out. I had to google a lil while to figure out what the electrical component was and specs. It is a 55V 110A, N-Channel, Power MOSFET, 3 Pin TO-247. Do I replace the single one or all of them? I already removed it from the board and included a picture of it for my post. Also there is still no signal whatsoever coming from any of my preamp outputs on my AVIC F900BT. I am assuming that I had some kind of power surge or spike that fried everything. I tested my DC voltage of my car battery (Car not running) and it is 11.8V. I have 1/0 AWG wire running from the from to the rear of my car. I tested voltage at my right before my distribution block and it was 11.8V. Then I chacked at each amp and read 11.8V. There was no voltage loss but isn't the voltage too low? I am a newbie but I have some schooling in electrical engineering so to say the least I have a basic understanding of electronic circuits. I am pulling the head unit next to check the pico fuse if I can find it and will post my results later. I hope some of you guys can help me along that maybe had a similar problem.

[Wicks]

Are you checking AC or DC voltage on the preouts?

You keep mentioning DC.

Unless you find out what caused the FET to fail, you could end up with the same or more damage.

[jtaylo82]

Are you checking AC or DC voltage on the preouts?

You keep mentioning DC.

Unless you find out what caused the FET to fail, you could end up with the same or more damage.

I checked both AC and DC to see if I got any voltage across the preamp outputs and I am getting nothing on my multimeter. This is strange because my Memphis amp is getting some kind of signal because it is playing normally. Do you think the low battery voltage could have possibly caused my FET to fail?

[Wicks]

Possibly, 11.8V is a bit

Low for a resting voltage bit I don't know what it would have dropped to when the damaged occurred.

What content are you playing when testing the preouts? (Test tone)

What volume, settings, etc?

[jtaylo82]

Possibly, 11.8V is a bit

Low for a resting voltage bit I don't know what it would have dropped to when the damaged occurred.

What content are you playing when testing the preouts? (Test tone)

What volume, settings, etc?

I used a 50Hz test tone at about half volume when I was checking. All stereo setting were flat including EQ. Maybe the voltage is so low that my equipment is not measuring it. I am positive my multimeter works because I gave me my voltage readings across the B+

[Wicks]

My Kenwood has 5V pre-outs. At half volume it measured 117mVrms so there isn't a very large signal at half volume.

For the sake of troubleshooting and just looking for signal flow, I would disconnect all speakers and max out the volume.

That way you have a nice and large signal (2-5V depending on HU) to measure so there should be no question.

Also use a few different test tones, if you have them, to double verify that you don't simply have some sort of crossover attenuation that's hiding your signal (you said your one amp plays music so there is a signal there).

If you need to test your meter on AC then insert the probes into a wall outlet (carefully, make sure you're not touching the metal tips of the probe).

Given, home AC is much larger but it should tell you if your meter is working or not.

While we're at it, what voltage is your alternator outputting with the car running?

You should also have your battery load-tested since 11.8V is pretty low for a resting voltage so your battery may be damaged (or just depleted).

Depending on the results of the load-test, put the battery on a good charger and give it a good charge overnight and see what it does.

[jtaylo82]

My Kenwood has 5V pre-outs. At half volume it measured 117mVrms so there isn't a very large signal at half volume.

For the sake of troubleshooting and just looking for signal flow, I would disconnect all speakers and max out the volume.

That way you have a nice and large signal (2-5V depending on HU) to measure so there should be no question.

Also use a few different test tones, if you have them, to double verify that you don't simply have some sort of crossover attenuation that's hiding your signal (you said your one amp plays music so there is a signal there).

If you need to test your meter on AC then insert the probes into a wall outlet (carefully, make sure you're not touching the metal tips of the probe).

Given, home AC is much larger but it should tell you if your meter is working or not.

While we're at it, what voltage is your alternator outputting with the car running?

You should also have your battery load-tested since 11.8V is pretty low for a resting voltage so your battery may be damaged (or just depleted).

Depending on the results of the load-test, put the battery on a good charger and give it a good charge overnight and see what it does.

So this is currently the deal. I tested the DMM in the wall socket. ACV=120. No problems here.

The next thing I done was i measured the voltage across the battery terminals with the car running. DCV=14.58

But here is the next thing I also tested. I put my battery on a trickle charger until fully charged and removed the charger. I immediately tested DCV across B+ car not running and DCV=12.8. I checked the same condition about 12hrs later and voltage dropped to my starting 11.8! Sounds like i need a new battery of course and I am going with an AGM but haven't decided which one yet. Moving along back to the amplifier I have ordered the replacement parts, also adding to my parts list I found one resistor burned on each side. Each was a 33Ohm resistor. I have ordered these at www.newark.com and they will be here Monday. As for my headunit goes........ which my post originally supposed to have been for........ and I apologize for choosing the incorrect discussion board..................... but I didn't really know what my problem was or is........But thank all who help so much