Why is my sub quiet?? :(

[cobbpa]

I moved from home into my college apartment yesterday. Now my subwoofer makes almost no noise (here the speaker in question). It buzzes & pops when I plug in the signal cable. If I rest my finger on the surround, I can feel it vibrating some, but really get no sound from it. All the settings are the same as I left them. I hadn't used it for a week or two, but it was great before moving. Any ideas?

[miner]

Sounds to me like the voice coil may be fried. Time for a replacement driver

[cjd]

Mm, sure. A move will sure fry a VC. Doesn't mean it isn't the problem, but...

Can you try a different amp? My first inclination would be something either mis-wired or an amp that had something rattle loose.

Test each part in sequence and with care and you'll figure it out.

C

[JRT]

Could be something as simple as a cold solder joint that may have loosened up and is now conducting very poorly.

[cobbpa]

Alright, I'll have to open it up and check wires. That may be a day or two before I can do it. I don't have another amp, but I suppose I could try connecting the speaker's leads to my receiver's outputs like a standard speaker...not 100% the best thing, but it could be a test at least, right? And how would I know for sure whether or not it's the voice coil?

[ThomasW]

It's fine to use the main speaker outputs to check the operation of the sub, provided you wire direct to the driver terminals, bypassing the sub's amp.

[cobbpa]

It's fine to use the main speaker outputs to check the operation of the sub, provided you wire direct to the driver terminals, bypassing the sub's amp.

Yes, this is what I was planning on. Unfortunately, after moving, I have little access to tools. We'll see what I can do.

[rom]

Hi,

I will be more cautious to try these suggestion from ThomasW

"It's fine to use the main speaker outputs to check the operation of the sub, provided you wire direct to the driver terminals, bypassing the sub's amp."

First , check if the RCA cable leads thats your feeding the plate amp is good or bad, try another one if you can.

It's possible that the volume control/level control on the plate amp was damage during the move, this can create similar outcome. Try adjusting the level and feel if you still have some kind of wiping action. It is also possible that the position was move and due to aging the contact losses on the carbon track.

If you taken the plate amp/the subwoof, I would recommend to use a penlight battery to test if the voice coil is still ok, this is done by connecting one teminal of the speaker to the battery and by a short tap on the other terminal, do not connect the speaker for long as this can damage if conneted for long, if the cone move and without any sign of rubbing coil to metal, Then proceed to hook then to your amp.

Suggetion from Thomas is OK if the driver is known Ok but if its shorted like a burned coil, the impedance could be low and if this is the case, I hope not, could damage your working amp as well.

It is also possible that your problem could only be a poor grounding connetion of your signal wire , RCA leads, as I suggest first, try that and could be all that it is.
I hope that help.
Cheers
rom

[Amphiprion]

[to the tune of the pink panther theme]
Dead amp, dead amp,
dead amp dead amp dead amp dead amp
dead ammmmmmmmmmmmmmmmmmmp dead amp

Seriously though, I had a 250w plate amp (Adire Audio AVA250) that stopped working after a move. My previous neighbor ran a TV&Radio repair shop for 30 years (man he was great to live next door to) and all it took was fixing a bad solder joint that had come loose. These plate amps aren't the highest quality things in the world.

[cjd]

Solder (or rather, solder joints) is simply prone to going bad when it heats up/cools down repeatedly.

Plate amps are built with as much quality as most other things...

C

[rom]

Hi Mark
I had a feeling that the amp is dead too but better test them first to find out.
Cold solder is most likely is the culprit.
Cheers
rom

[Amphiprion]

Solder (or rather, solder joints) is simply prone to going bad when it heats up/cools down repeatedly.

I'm sure that's why it worked fine for 2 years and then never worked after the move from Tucson to Hot Springs.

[cjd]

Yup.

The one thing is that sub amps *do* tend to get pretty toasty when in use, so they get more extreme swings than average (made worse by the generally barely adequate cooling).

So, no surprise.

C

[cobbpa]

I've tried different interconnects; that isn't the problem. I'll try & get tools to open it up this weekend, see what happens if the sub gets power from elsewhere and if I can spot bad solder joints. How obvious would a cold joint be? Are you talking a broken joint with loose wires, or just a cloudy & possibly cracked joint?

[cjd]

You wouldn't notice a bad solder joint by inspecing in all liklihood.

C

[Brian Bunge]

You wouldn't notice a bad solder joint by inspecing in all liklihood.

C

Ain't that the truth! My $5K Pioneer Elite TV died after just 2.5 years of use. Unfortunately, Pioneer wouldn't fix it under warranty and after being dead for 2.5 years I found a thread on AVS where almost 100 other people had the same problem. Luckily, others found out that there were specific connectors on the PS board that had cold solder joints. It literally took me less than an hour to fix my TV and not one of the joints "looked" bad. What's even more saddening is that Pioneer totally denies any PS board issues with the x10HD series of TV's.

[Arneson]

I've seen two that had physically broken solder joints right at the input plugs.
The plugs are tight, and were stressed when first the connectors were plugged in, and again when the plugs were pulled out.
Went right to it and soldered them good as new.

[cobbpa]

Alright, opened it up finally.

Amp --> speakers = no output.

Receiver power --> sub = cone movement & noise.

So the amp is bad but the sub is good, right? And I hear turn on/off pops and get a little (as in, almost none but I can feel the surround vibrate occasionally) sound. This would point to somewhere in the amp's power stage, if I'm guessing right. But the trouble is I have no idea how to go about diagnosing it from here. Ideas? Or is it hopeless and time to make myself step up to a nicer setup?

[cobbpa]

I have had no time since the last post to examine the amplifier its self, and really haven't the slightest idea at where to start. Here's a picture, anyone want to suggest where a problem might be? Again, to summarize what I can recall, I believe it's getting signal and the amplifier does have power but power is not getting to the sub its self. Any ideas...anyone? I'd like to get this fixed for now and eventually upgrade amp / sub, but that has to wait...so if I can't fix this, I'll have to keep going on without a sub

[chasw98]

I have had no time since the last post to examine the amplifier its self, and really haven't the slightest idea at where to start. Here's a picture, anyone want to suggest where a problem might be? Again, to summarize what I can recall, I believe it's getting signal and the amplifier does have power but power is not getting to the sub its self. Any ideas...anyone? I'd like to get this fixed for now and eventually upgrade amp / sub, but that has to wait...so if I can't fix this, I'll have to keep going on without a sub

All the following suggestions can be very dangerous because they require you to turn on the amplifier and take measurements while the amp is live. You could electrocute yourself at the worst and ruin the amp at the least.
BE CAUTIOUS!

Do you have a voltmeter? If you do, there are some simple tests you can do to troubleshoot the solid state amplifier. If not, send it in for repair.

01) Check and see if the secondary side of the power transformer has any voltage coming out of it. You will usually find 3 wires that are output 1, output 2, and the common between the 2. You should measure between 30 and 60 volts AC between the output and the common on both sides.

02) If you have AC voltage there, the next step is to determine if your power supply is converting the AC into DC voltage. There should be a diode bridge that will have 2 AC lines from the secondary of the transformer connected and 2 other wires connected. The 2 other wires connected should have between 25 and 50 volts DC on them as referenced to ground.

03) If you have DC voltage present at the power supply, then you could check the output transistors of the amplifier to see if they are receiving DC voltage on one of the three leads they have. If they are, then the other 2 leads will have readings like a very small voltage on one and a medium voltage on the other. If you find that all 3 leads have the same DC voltage that you measured on the power supply, you probably have shorted output transistors and the amplifier circuit might have other components damaged.

This is a very simplistic method to determine if you have component damage to your amplifier. If you slip with your probe, you could hurt yourself and most certainly for sure damage the amplifier. If you do not feel comfotable doing this, DON'T DO IT! Take it to a service tech or send it in to the manufacturer for repair.