amp problems

[SupraStar 3000]

PLEASE HELP!!
Installed a Infinity Reference 5760a amp running off speaker line level
inputs on all 4 channels (pluss two 10" subs).

Runs perfectly for 2 days, then on 3rd day power/protect/clip LEDs start to flash and amp keeps switching OFF and ON intime with high peaks in music.

Turn internal sub signal to external and amp runs fine with 4 speakers but without subs. Turn internal signal back and subs work but with original problem.

3 independent experts have check the system and can't find any problems from amp, siginals, earth, power (4-gauge power and earth), remote power etc. They ALL tell me it must be a faulty amp.

I send the unit back for tests but according to the shop its works fine:
The amplifier was left on a test bench for more than 2 hours with
4-speakers and a 15" Rockford Fosgate subwoofer connected. During this
period it did not clip, overheat or shut-down.
The amplifier lights did not go into protection.

so, back to square one!

..any ideas???

[Matt Harwood]

It does sound like a power supply fault.

Easy way to test. Get yourself a multimeter, (analogue could actually be better, but not essential).
Connect the meter with stereo playing normally and with all channels driven, at a lower level than the point where it cuts out.
The reading on the meter should be around 12v. (probably higher if the engine is running). Now turn the volume up to where it starts to cut out. If the voltage fluctuates badly, then the power supply isn't strong enough to power that amp.

Note, a power supply fault could be many things. A poor terminal connection at any of the terminals. Bad fuse connection, bad battery connection, bad earth connection, bad earth location...

[SupraStar 3000]

Thanks Matt,
I was hoping you'd find this thread :)

Good idea, I have a multimeter and will give it a try when I get the amp back from the shops.

I too thought it was a power problem but the 4-gauge power and earth seemed fine when I checked it last. The earth point is a standard location for the car and already included earth for fogs and lights in the space saver wheel well.

I have two new fuse box's and fuses (those gold bling ones) and even bought a brand new battery for the car.

Lets hope it is something simple like power.
Cheers for the help!

[SupraStar 3000]

PLEASE HELP, BECAUSE THIS IS DRIVING ME MAD :looney:

I'm confused!,...... totally confused!!

multimeter test seems to show I have a GOOD power supply without any fluctuation at high volume which is strange because I was sure it was a the power problem!

Amp tested ok! (by factory)
Power tested ok! (by me)
Remote tested ok! (by mate)
Subs seem ok! (see below)
Earth tested ok! (by me)

Heres the weird bit:
During the test I accidently disconnected the right sub and the system started working fine! I thought that maybe it could be a faulty sub.
So I reconnected the right sub and was surprised when both continued working even at high volume. Then as I tightened the output screws on the amp the problem started again.
So, again..... disconnected the right sub, amp started working reconnected the right and tightened the output screws but this time amp continued to run.
Checked all the connections and spades but everyting seems fine.

Currently everything runs ok but I'm sure after a while I get the same problem again!

seems that fiddling around with the order I conect the + and - corrects the problem. But is intermittent and has no relevance to left or right sub!

Any ideas?

[The Hornet]

Is there any chance that any of the + & - connections to your speakers / sub are shorting to each other as this would create that effect. and would be intermitant if there only shorting out now and then.

[Matt Harwood]

When you tested the voltage, did you measure it between the positive and negative on the terminals of the amp? - Not by using a different earth point...
If that's how you tested it and it still read a good solid voltage, I'd start suspecting the amp to be faulty. Going by your description, it could be that there is a bad joint inside the amp causeing an intermittant problem.

Out of interest, can you tell me the EXACT models of all the speakers you have connected to this amp, and how it's currently configured?

[SupraStar 3000]

Matt,

Heres the specs:
PIONEER FH-M75 (CXA4747 part No.) Jap Import headunit
INFINITY Reference Series 5760a amp (6 chl)
INFINITY Reference Series 1030w Subwoofer LEFT
INFINITY Reference Series 1030w Subwoofer RIGHT
INFINITY Reference Series 625i 6 1/4" REAR
INFINITY Reference Series 452i 4" FRONT (fits toyota door box)

Head unit doesn't support RCA line outputs so amp uses high level input from head unit to power fronts and rears. Subs also take feed from high level input using all 6 channels.

[SupraStar 3000]

Hi Hornet,

connections and shorting was the first thing I thought aswell but i've checked and double checked all the wires.

[SupraStar 3000]

Hi Matt,

I used the same earth point as the amp uses and the power connection for the tests.

I'm going to borrow two subs from a mate just to eliminate the subs next week and see how the system runs.

[SupraStar 3000]

Here's the wiring diagram.

[Volvarine]

Hi, I wonder if you guys can help me I am looking for the wire layout on the Poineer FH-M75, basicly the layout of the plug on the back, or maybe a installation manual would be helpfull.