TR-S2K

On the way to work this morning, suddently no sound from both front and rear speakers, only subwoofers are working okay (I can hear the bass and nothing else). I did not have any chance to debug the problem(s) yet. What should I check first ? Are these steps okay ?

1 Fuse in power line from battery to power amp
2 Fuse in power amp
3 Ground of power amp
4 RCA's from HU to power amp
5 Speaker wires from power amp to speakers

PJK3

1-5. yup. fuses first for sure.

to make it easier, use that meter and check for voltage from the hot to ground at the amp's power lead, also check at the amp turn on lead.



(do you still have the Bose sub? i don't recall. and in case i'm wrong, are we talking about 1 amp? or 1 amp on the sub and 1 on the highs?)


if those don't work -- it gets harder. i'll try to check the site tomorrow, and if you're having problems, i'll PM you my number.

dbzerk

Have you checked the lights on the amp to make sure it isn't in protection mode?

How many amps are you running?

TR-S2K

Thanks guys.

I have one 4-channel amp (Memphis MC-2004) driving 4 speakers (2 fronts and 2 rears), plus 2 Bose subs each has its own amp. Bose's amps got Sub-woofer signal directly from Nakamichi HU. Memphis amp's inputs are connected to HU's RCA outputs.

I checked the voltage from the power to ground at the amp's power lead, also checked at the amp turn on lead, both were okay.

The problem was with the 4-channel Memphis amp. I checked the fuses of power line from battery to 4-channel amp and the amp's fuse, both of them are okay. I then checked the 3 LED's of the 4 channel amp: Green is nornal, Yellow is blown fuse, Red is internal error (or pretection mode ?) and no LED was on. I turned off the HU, wait for few minutes, then turned it on again while watching the LED's, what I saw was the Red LED turned on for about 1 second, then off. After that no LED was on for as long as the HU was on.

The Memphis amp owner manual does not say anything about protection mode, what I should do when the Red LED turns on for a second.

I will contact Memphis service center to see if they can help to debug this problem.

PJK3

i'd disconnect all the speaker wires from the amp, and see if it will power up w/o them being connnected.

also, while they are disconnected, use your meter to check their resistance. they should all come back around the low to mid 3.x ohm range.

also, power the amp up and measure the voltage across each speaker output + to - (assuming the amp stays powered up long enough to do this...)

now, i'm very curious.

TR-S2K

Thank you Phil,

I will do the three things tonight as recommended:

1. Disconnect all the speaker wires from the amp to see if it will power up.
2. Check speakers' resistance - should be 2 to 6 ohms.
3. Power the amp up and measure the voltage across each speaker output - should be more than 5 volts at low to medium volumes.

Until now, I think the problem is the Memphis amp. It got into protective mode and no way to get out. The volume at the time the 4 speakers went dead was medium low, about 90dB to 95dB, or about 2 watts to 3 watts max for less than 10 minutes pay times. The top of the amp was not even warm at that time when I touched it (it is mounted under driver seat)

PJK3

yeah. the amp seems suspect. if you developed (for some weird reason) a short in the speaker leads for any speaker (sending them to ground or shorting somehow), it could cause the amp to do some weird things, including power down via protection.


as i recall, isn't that a T-class amp? (i'd look, but as i recall to get Memphis product info, you've got to download their 50 page PDF at 10 MB... not gonna happen at work.) if it's digital, it could definitely behave differently than a traditional amp, and act very funny if shorted.


if the thing won't power up w/ no speakers connected, and the speaker resistances are good (around 3.3 or so), and you get the red light (fade away) from the amp or no voltage across the speaker outs (w/ a minimal signal)... the outlook for the amp may be grim i'm afraid.


another thing to check -- w/ the speakers disconnected... measure the resistance from each speaker lead to ground. i think they should all be infinite when checked (no continuity). that should also cover a 'short to ground' in the speaker wire. the other measurement (resistance in the speaker) will check for a blown speaker more than anything...


....*thinking of anything else to check*.....

also, look for any loose wire filings or conductive materials that might be bridging a gap between any leads.

you might also want to knock/rap on the amp a bit. no more than what you might use to knock on a door. if after a few knocks, the amp comes back to life, you might have a loose internal solder joint.
(yes, highly pro thing to do... i started doing this as a 'troubleshooting' technique after having a very troublesome amp that would randomly shutdown and come back to life. it was getting the best of me after a few weeks of on and off again... it would quit, i'd dismount it, look for problems, and it would fire up fine... eventually, i just got frustrated, gave it a whack (revenge) and the dang thing worked. i opened the case, checked for gaps and measured for continuity all over, and found a bad solder joint... a touch up solder and a few minutes later, it was fine and worked for quite a while till i sold it. last i heard, it was still working fine.)


best of luck, let me know how it goes.

TR-S2K

I did all these steps and the conclusion is, the amp is dead. This Memphis amp is AB class. I am trying to contact the seller to see what they can do for me, hopefully, they will exchange my dead amp for another one.

1. Dis-connected all the speaker wires from the amp, power up the HU, the amp red LED "on" for 1 second then off, just as before dis-connecting speaker wires.

2.. Speakers' resistance are between 3.2 to 3.8 ohms

3. Power the amp up and measure the voltage across each speaker output + to - : zero volts

4. All speaker + terminals to ground were infinite, no shorted

One thing I did not do is knocking on the amp, I do not like to cause any dents on the cover, then the dealer may not take it back. If I can not return this amp, I will then do the knocking.

I am thinking about this plan, if I need another amp, I will get a 2-channel amp of about 100W/ch to drive the front Kappa Perfect 6.1, and using the Nakamichi HU internal powers to drive the rear, since the rear speakers is for rear fill only, I do not need more than 10W/ch for rear fill. Which 2-channel amp do you recommended ? This amp should be small enough to be mounted either under driver seat or behind either driver or passenger seat. If I can fix this amp, I will bridge the 4-channel to 2-channel to double up the power for front speakers, and rears will be powered by HU.

Thanks Phil , and have a great weekend.

PJK3

aw... bummer. yeah, it is sounding grim for the amp.

regarding knocking on the amp? dents?? good God man! i said knock, like you would on a door... do you have hands of steel? we're just talking tapping here, not pounding!
i can understand, and appreciate your discomfort. my amps (and other amps i've used that on) have been out of warranty...

your plan sounds pretty good... what kind of fundage are you looking to spend on the amp?
(i'm honestly not sure how much space you have to work with...)

i know i have been very pleased w/ the Boston amp i put in my wife's Ody. the GT-22 is 2 x 75 Wrms @ 4 ohms (12 V DC, so likely to make close to 100 Wrms when close to 14 V). it is fairly small. 2 1/4" high and 12" x 9"
chances are -- that's a bit too big (unless you put it behind the seat) and likely to be fairly expensive unless you can strike up a deal. the good thing tho, is that they are rumored to be an Audison design.

more realistically, the newer Clarion amps don't sound bad at all, are quite affordable, and are pretty darn tiny.
the APA 2160 is around 80 Wrms x 2 @ 4 ohms. it is like 6.5" x 2" x 11.3"

of course, there are the JL Audio options. i know William (WLaurent) has a 500/1 wedged behind his passenger seat. it's the same size as the JL Audio 300/2 which is 150 Wrms x 2. and it's 13.4"L x 9.25"W x 2.36"H


so -- there are 3 options i'd be considering... i'm sure there are more, but those are the 3 smaller amps that came to mind for me (right away at least).

hope those help.

TR-S2K

Thanks Phil,

The Bostom amp seems can be fitted under driver seat. It is about the same size as Memphis 16-MC2004. I have no problem spending $ on my ICE, the problem I had was I do not know what is good what is not, and I do not care much abount bling factors, all I like is quality.

I would like to know before hand that if I can not re-use this Memphis amp, what are options do I have. I do not know much and have no experience whatsoever with car amplifiers. If you like Boston GT-22, then it must be a good amp. If there is one person on this board that I acn trust completely, it is you my MAN.

Thanks so much for your helps, and have a great weekend. If you ever have a chance to visit DisneyLand, I will buy you some beers.