Half my Channels are dying! :(

idoseadoo

Member
2016-05-10 8:24 pm
Hey Everyone!
I'm new to this forum and am hoping someone can help me figure out what to do about my amp. I've spent the last two years building the perfect boat, and now that it's back up and running with the new and improved engine, I want to enjoy those lake days again, but how can you enjoy a boat without a good sound system?
Anyway, I have an 800W marine PowerAcoustic Amp. It has 4 channels. Two are bridged to a 10" Bazooka sub, while the other two run to two beefy Polk marine speakers.
The boat (and sound system) have been sitting (sometimes outside, sometimes inside, but the amp has always been in a place where it doesn't get wet) while I've been doing all the crazy modifications. When I finally hooked the sound system back up, I noticed that the left speaker was playing more silently and a bit raspy. I didn't mess with it again for a few days and the problem seemed to go away when I turned up the sound. I thought it was just a fluke, but then the problem came back and worse. So I used the head unit to compensate more sound to that side. Then, the speaker made a popping noise and came back to full loudness. I set the channels equal again and the problem didn't appear until recently. Now the left channel is almost silent (but not completely). Is this something dying in the amp?

I have experience soldering and replacing circuitry. Will it be obvious what's wrong if I pull the cover off? Is there a test I can do?

Thanks, I appreciate any help. I'm an engineer, so I welcome any and all technical info. Anything to help me not have to buy a new amp, as I really like this one (when it was working).

Also, if you want, you can see my thread on the boat build by searching for 4tec Challenger Upgrade. It's on the SeaDooForum :)
 
Last edited:

gpapag

Moderator
Paid Member
2002-11-17 6:42 pm
Athens-Greece
Hi idoseado and welcome to diyaudio.com

I would suspect corrosion.
With power off, exercise all the plugs and connectors external to and internally.
If you are operating in salty waters, consider removing the audio system from the boat when not in use for more than a few days, because the salt will eventually do damage at the components level too.

George
 

idoseadoo

Member
2016-05-10 8:24 pm
Thanks for the fast replies! It's not in salt-water, just lakes. I did try both speakers on the good side, and they both sound good. I even tried switching the pre-amp (are they called RCA?) plugs around to no avail. If it is corrosion, is it something that can be cleaned up if I remove the cover? I've heard that brushing it with baking soda/water and rinsing with alcohol can help clean corrosion off the boards...
 

gpapag

Moderator
Paid Member
2002-11-17 6:42 pm
Athens-Greece
If you have exercised all the external connections and have checked all the interconnecting wires for continuity, open the cover and see if there are any male-female connectors inside or any terminals on the printed circuit boards. Exercise these too.
See if there are any fuses on fuse holders. Remove the fuses, check if they are not burned and reinstall.
If there are any dip switches, notice their position, exercise them a few times and bring them back into the original position.


If it is corrosion, is it something that can be cleaned up if I remove the cover? I've heard that brushing it with baking soda/water and rinsing with alcohol can help clean corrosion off the boards…

Well, that may be tricky. I would use a magnifying glass to look for corrosion on the component leads.
If there is corrosion, cleaning the way you have described is OK. But you have to rinse the boards and dry them very well.

George
 

idoseadoo

Member
2016-05-10 8:24 pm
Could Low Voltage have anything to do with it?

Could low voltage cause half of the channels to be low? I ask because that is a possibility. This is running off a dedicated deep cycle battery that is charged before each outing (ideally) but sometimes I forget... I have no idea what the power is, and won't be able to check it for a couple days as I'm away on business this week.
I read posts where this can damage power supplies, but what about the other internals? Or could it just not have enough juice to power them? Or could the power supply be PARTIALLY damaged and not be feeding half the amp what it needs?
 
Could low voltage cause half of the channels to be low? I ask because that is a possibility. This is running off a dedicated deep cycle battery that is charged before each outing (ideally) but sometimes I forget...

i know that phenomenon from a outdoor system.
as soon as the battery charge level gets too low one channel of a two channel module fails.
it is always the channel i use for highs.
i get the same effect if i use a smps with (too) low current rating.
 

idoseadoo

Member
2016-05-10 8:24 pm
i know that phenomenon from a outdoor system.
as soon as the battery charge level gets too low one channel of a two channel module fails.
it is always the channel i use for highs.
i get the same effect if i use a smps with (too) low current rating.

Is the amp damaged, or do I just need to charge up the battery? If it is damaged, what gets damaged?
Thanks!
 

idoseadoo

Member
2016-05-10 8:24 pm
sorry, i forgot to mention that everything works fine with recharged batteries.

Not so sure that's the case. I toggled the switch to bridge the Starting and Accessory batteries, and brought the voltage up to 12.4V. The left channel was still more silent than the right. Perhaps I need to adjust the gain on that channel. I will test again once I finish charging the Deep Cycle. It's on a 2A trickle charger now (and has been all night).
 
Does this amp use a relay for speaker protection?
If yes, then there is a good chance that your headache is caused by corrosion of the relay contacts.

I am not sure about that. I didn't get a chance to mess with the gain or any of the other dials this weekend, had company over from out of town. However, while we were using the boat, the bad channel came back for the 2nd part of the day. When the head unit had them equally balanced, they sounded equally loud. So it's not that the gain knob maginally turned. Something has got to be corroded, or otherwise making a bad contact. Also, the bad channel, while quiet, will sometimes make a cracking popping noise.