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Help me Troubleshoot.

1039 Views 8 Replies 4 Participants Last post by  Graham_A_M
Current Setup:

Battery is connected via 1/0 ga with breaker to 1.5 Farad Capacitor.
Capacitor is grounded to existing common ground for the trunk of the car via 1/0 ga.
Capacitor is connected to Amp via 4 ga for both + and -.
Remote lead is connected to the remote output of the factory head unit.

Factory head unit is used.
Line Output converter is attached to the rear speaker wires, and grounded to main dash support. (Continuity is confirmed.)
LOC is then connected to the AMP via RCAs. (With volume at 50%, I was only able to get about .3 VAC out of the RCAs while playing a Bass heavy song.)
Amp is connected to 2 subwoofers.

So here's the deal. I hooked everything up and flipped the breaker on, the voltmeter rose and held at 12.40 volts and the LEDs started to flash on the capacitor. Which means there should be no issue with the power supply, but incase there was, I moved the ground to a couple different locations as well as put the multimeter on it. Everything checks out.

Turn the car on and the CAP's voltmeter jumps to 14 volts. Amp power light turns on. Once again proving that power shouldn't be the issue.

Turn the radio on, and insert CD, music can be heard through all 4 door speakers, but not through either of the subs.

Troubleshooting that I have done so far:
  • Pulled the head unit out and tested the continuity of the LOC connections. (Much less than 1ohm for all 4 of them.)
  • Tested VAC of LOC output. A bass heavy CD only netted .3 VAC at 50% volume. (BTW, I believe the output for the LOC is rated for 1.2V)
  • Adjusted the Gain, Crossover, and EQ knobs on the amplifier, as well as the knob on the LOC.
  • Disconnected and reconnected the speaker wires and RCAs. (No sounds coming from the subs what so ever.
  • Tried plugging my iRiver directly into the amp in order to try and find any signs of life. (Nothing happened)
  • Replaced amp fuses. (The old ones checked out, but I wanted to be sure.)
  • Metered the output terminals on the amp, and didn't come up with much if anything at all. (But if it's not getting signal, it wouldn't have anything to output, correct?)

I've already ordered a new LOC in case that was the problem. Is there anything else I can do to try and troubleshoot this problem before buying a new amp?
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1 - 9 of 9 Posts
I'm quite sure its your LOC output voltage. 0.3 volts is very very little. 1.5-7 volts are common. 0.3 is so low, your amp may be disregarding the signal entirely, because its interpretting that as noise.

What I'd do (to troubleshoot if it IS in fact the LOC) is use a home stereo CD player (as an example) and hook up the RCA output from that directly to your RCA inputs on your amp. Then turn the amps gain controls down, much as you would using them as if they were a volume control.

Play that CD, and slowly turn the gain(s) up on the amp. You should have sound. If not, its (almost) certainly the amp itself. What kind of amp and LOC are you using?
MTX 4250D amp.
Tsunami FL-LOC600 Line Out Converter.
If you can borrow an amp, then hook that up and see if you're getting any sound out of the subs.

My old deck had a .5 volt pre-out, and the amp read that signal just fine, so .3 volt shouldn't be a big deal. The manual will give specs on input voltage, so if you have that give it a quick read.
1. Gain Controls – These controls are used to match the input sensitivity of the amplifier to the particular source unit that you are using. The controls are factory set to 1Vrms.
4. RCA Input Jacks – RCA type input jacks for use with source units that have RCA or Line Level Outputs.
A source unit with a minimum output level of 200mV is required for proper operation. However, this input
will accept levels up to 8Vrms.
Sounds like it is the amp.
Agreed - sounds like the amp. If you were closer I'd let you borrow the one under my bed to test, but EDITED

Almost told you where PEDOBEAR LIVES
HAHA, I'd borrow your amp any day PEDOBEAR. That ended up being the problem anyway. Bought a used amp with warranty off ebay for $16. Works like a champ, and is an upgrade from the old one.

Almost told you where PEDOBEAR LIVES
No need to, Pedobear is where the CP is, much like God, he is around you and everybody all the time. (Well not everybody, just those under 18)
1 - 9 of 9 Posts
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