Subwoofer plate amp FIRE. - AVS Forum
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post #1 of 21 Old 02-11-2013, 06:41 PM - Thread Starter
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I woke up the other day to the smell of burnt plastic. I didn't hear any noises or see any smoke and my smoke alarms didn't go off. I thought it could be my neighbor since I live in a duplex. A couple of days later I went into my second bedroom to listen to some music. My sub was dead and no LED on the back. Next I pulled the fuse and it was blown. I had a spare fuse so I put it in and the LED would switch from red to green but still no sound. A few days later I pulled the amp and was shocked at what I found. A capacitor had exploded and caught on fire. It leaked onto the circuit board below it and burned completely through the board. Many of the surrounding areas where covered in soot as you can see in the pictures. A few spots on the MDF around the cut out for the amp have burn marks in them. The MDF was very close to catching on fire. In total I have five subwoofers in standby mode in my house. Four in my main theater and one in my second bedroom. They all have the same Bash amplifier. I'm worried this could happen again if I leave any of these amplifiers in standby mode. I think one of my only choices is to turn all of them on and off manually after every use to prevent burning my house down. The other option I'm considering is removing all of the plate amplifiers and using a large pro amplifier I have sitting around to power all four subs. I think I could wire two subs in parallel on each channel on my two channel pro amplifier. I don't want to alarm everyone but this is dangerous.

Amp fire 1.jpg 617k .jpg file
Amp fire 2.jpg 575k .jpg file
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post #2 of 21 Old 02-11-2013, 06:48 PM
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How about some more details? You built these subs?

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post #3 of 21 Old 02-11-2013, 06:52 PM - Thread Starter
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They're all pre built purchased subwoofers. All Cerwin Vega CLS15S subwoofers. I'm only sharing this because they have Bash plate amplifiers. Many other subwoofer companies also use Bash plate amplifiers. I know this isn't the first time a plate amplifier has done this. I read that some plate amps that ED was using also did this. I'm not sure who produced those plate amps though.
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post #4 of 21 Old 02-11-2013, 07:11 PM
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in that first pic you can see that the large filter cap was leaking. That most likely caused the failure. many companies fall the victim of purchasing lousy caps unbeknownst to them.

After a few years I alway open up my equipment and look for bulging
or leaky caps.

Many times this preventive measure will save lots of gear. I saved about 5 pieces of equipment over 10 years by doing this.



Athanasios


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post #5 of 21 Old 02-11-2013, 07:14 PM - Thread Starter
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You're right. I noticed that bulge on the cap. Maybe I will pull the plate amps on the rest of my subs and check the caps. Thanks for the tip.
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post #6 of 21 Old 02-11-2013, 07:28 PM
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Are you also sure it burned a hole in the PCB? Some PCB's have slits under the filter caps incase they do blow they have a place for the gasses to escape.
Clean it up with denatured alcohol and inspect it closer. If your handy with a Solder iron. remove those diodes and check them.

I bet you only need to replace the cap and the diodes. maybe a resistor or two.

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post #7 of 21 Old 02-11-2013, 07:33 PM - Thread Starter
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I will take a better look at the board below it and report back. It's a little difficult to see. It looked like it had stringy spider webbed melted plastic. That can't be good. I'm good at soldering so if I need to solder that wont be a problem.
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post #8 of 21 Old 02-11-2013, 07:40 PM
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Maybe some pics of the under side?

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post #9 of 21 Old 02-11-2013, 07:59 PM - Thread Starter
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I removed the screws from that circuit board to get a better look. It doesn't look good. It looks like a hot mess.
Burned Curcuit Board.jpg 744k .jpg file
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post #10 of 21 Old 02-11-2013, 10:12 PM
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The PCB trace right there is toast. That stringy stuff is the smoky by-product of the board burning.

New board time.

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XT32 rocks!

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post #11 of 21 Old 02-11-2013, 10:25 PM
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Holy Shite!!!!!

yeah toss that amp!!!

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post #12 of 21 Old 02-12-2013, 05:20 AM - Thread Starter
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In the past I have had another one of these amps die on me. It was just a diode that failed. No fire. It was fixed under warranty. Now I have no more warranty left on any of the subs. I'm not sure if the plate amps are available from CV anymore. The last time I checked several years ago they where available for $300. So I don't think buying a new amp is possible. Lucky for me I do have some spare plate amps and drivers for these subs. I got them off Craigslist just in case something like this happened. I didn't think they would catch on fire though. I'm really considering pulling all of these amplifiers and turning all four of my subs in my main room from active to passive. I will make some amp block off plates and install some speaker binding posts in the block off plate. If I remember the Bash amp is 250rms and 300w peak. The driver in each sub is 4ohm. My pro amp is 2ohm capable and makes 600w at 8ohm in stereo mode. Do you think the outcome would be fine if I wired two subs per channel in series? Wired this way each channel would power two subs and see an 8ohm load. In the past I have used the gain matching method for calibrating so I would use that again with the gains on the pro amp. Any opinions on this? Positive or negative. By doing this I already know I will be avoiding exploding caps catching on fire.
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post #13 of 21 Old 02-12-2013, 06:39 AM
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Quote:
Originally Posted by Secret Squirrel View Post

In the past I have had another one of these amps die on me. It was just a diode that failed. No fire. It was fixed under warranty. Now I have no more warranty left on any of the subs. I'm not sure if the plate amps are available from CV anymore. The last time I checked several years ago they where available for $300. So I don't think buying a new amp is possible. Lucky for me I do have some spare plate amps and drivers for these subs. I got them off Craigslist just in case something like this happened. I didn't think they would catch on fire though. I'm really considering pulling all of these amplifiers and turning all four of my subs in my main room from active to passive. I will make some amp block off plates and install some speaker binding posts in the block off plate. If I remember the Bash amp is 250rms and 300w peak. The driver in each sub is 4ohm. My pro amp is 2ohm capable and makes 600w at 8ohm in stereo mode. Do you think the outcome would be fine if I wired two subs per channel in series? Wired this way each channel would power two subs and see an 8ohm load. In the past I have used the gain matching method for calibrating so I would use that again with the gains on the pro amp. Any opinions on this? Positive or negative. By doing this I already know I will be avoiding exploding caps catching on fire.

Since you have the spare amps why not just recap them. Get higher quality Caps like the Panasonic FC, FM. or FR series from Mouser.com.

Usually large companies like CV use the cheapest parts to save money. In many cases changing cheap parts with higher quality or newer versions will help a lot
in audio equipment. Its Called P.O.O.G.E ing Progressive Optimization Of Generic Electronics . There was a series of articles on this in the Audio Amateur magazine.

Lots of great info there on Soft recovery diodes caps resistors etc.

It's lots of fun taking a so so amp or pre amp and making sound a lot nicer or just last a lot longer.

Athanasios


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post #14 of 21 Old 02-12-2013, 01:39 PM
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Why not just house the plate amps in separate metal containers
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post #15 of 21 Old 02-12-2013, 07:53 PM - Thread Starter
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That's an idea but I think if I'm going to remove all the plate amps I will try and use my large pro amp to power all four subs. That would require only one amp to turn on. I'm not leaving those plate amps on anymore. So now I need to flip four switches with the plate amps. I did a test of the driver on that sub with the plate amp that caught fire. Luckily the driver seems fine.
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post #16 of 21 Old 10-22-2013, 10:05 PM
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Hey Squirrel,

Any chance you can pull the amp off one of your other CLS-15S and take a picture of the undamaged circuit board (# 600131 Rev3)? Mine just blew and the I'd like to rebuild mine, but the traces are all burnt up and I need to see how they originally were.

Please post up a pic. It's hard to find another plate amp that fits the 8.25"W x 9"L dimensions.

Thanks.

tk
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post #17 of 21 Old 10-23-2013, 05:02 PM - Thread Starter
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I would like to help you out but I don't really want to pull a plate amplifier from a working subwoofer. The factory seals on the amplifiers I've already removed where difficult to break. I took some pictures of the circuit board that you're looking at on the burned amplifier that I have. The circuit board isn't damaged bad on top so maybe you can find what you're looking for. I would just buy an outboard dedicated amplifier instead of trying to find another plate amplifier. There aren't any that will really work. I have a spare pro amplifier that I'm going to use to power these subs when more of the plate amplifiers go out. I'm going to make some block off plates for the back of the subs and put speaker binding posts on the back of the subwoofer. I also plan on using an inline FMOD low pass filter in line with the subwoofer cable. The Bash plate amp has a LP filter in it. I already tested for it.
Plate Amp 1.jpg 216k .jpg file
Plate Amp 2.jpg 204k .jpg file
Plate Amp 3.jpg 222k .jpg file
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File Type: jpg Plate Amp 2.jpg (204.3 KB, 12 views)
File Type: jpg Plate Amp 3.jpg (222.2 KB, 16 views)
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post #18 of 21 Old 10-24-2013, 09:42 AM
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Thanks Squirrel. I was hoping that with all the previous suggestions of upgrading capacitors, that maybe you had and took pictures. I have a choice of getting a new 12" powered sub or a replacement plate amp. It's just hard to give up a 15" sub.
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post #19 of 21 Old 10-28-2013, 11:08 AM
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Just got an older Rotel RB-890 (from the early 80's?) off some guy from Craigslist for $80.

After I got it home, I took it apart to see new-ish (not original) transistors on one of the channels. There was also the stains of what looks like Coca Cola at the bottom of the case. One of the channels has a broken board trace leading to a resistor which has one of its legs broken (resistor leg was sloppily soldered back together, which didn't hold). 3 of the 4 fuses were wrapped in thin bare wire and put back in place.

I worked on the amp (replace 4 internal fuses, took the electronics out of one of the channels to clean up a past soda spill at the bottom of the heat sink, fixed an electronic circuit board trace that was burnt out, and re-soldered a resistor that had one of the legs broken directly back on the board). I went through both channel boards and figured what the heck, let's plug it in, turn it on with nothing attached and see if anything smokes (so far so good).

Then I had to modify my CV CLS-15s to bypass the burnt out internal plate amp and connect the external amp to it. I didn't want to make a new plate for it, so nstead I just took the fuse out of the Bash amp, cut the internal power wiring and used one set of the speaker posts to directly connect to the subwoofer driver). In order to eliminate confusion, I just unscrewed the rest of the unused posts from the busted Bash amp and to my surprise they completely unscrewed. I'm using it in bridged mode with the 15" sub.

From what I was able to google, the Rotel has power rating of 160W x 2 or 350W x 1 into 8 ohms; 250W x 2 into 4 ohm.

After a recalibration of the sub level, I find the sub to be flabbier sounding than I remember. I'm now contemplating building a sealed sub.

All in all, I think it was worth the 80+ mile round trip.
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post #20 of 21 Old 10-28-2013, 11:15 AM
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Are the amps UL listed? Just wondering.

This is another reason I shut my amps off when not in use. I also unplug stuff around the house when not in use or something I don't fully trust. I know somebody that lost a brand new home years ago. They moved in and only lived in the house a few days and while they were out a brand new appliance never even used caught on fire. Pretty sad, he built the house himself.

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post #21 of 21 Old 10-28-2013, 11:30 AM
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Quote:
Originally Posted by Reefdvr27 View Post

Are the amps UL listed? Just wondering.

This is another reason I shut my amps off when not in use. I also unplug stuff around the house when not in use or something I don't fully trust. I know somebody that lost a brand new home years ago. They moved in and only lived in the house a few days and while they were out a brand new appliance never even used caught on fire. Pretty sad, he built the house himself.

The Bash plate amp is UL and CE rated.

From the post mortem examination of my plate amp, it looks like the same capacitor blew on mine as it did with the OP's (pics in earlier posts). The bottom of the board shows that it burnt through the circuit board, and there were burnt marks at the aluminum plate that the board is attached to as well. In my case, the rest of the amp still worked (goes from standby to on when bass is sensed from the receiver), but with no output at the subwoofer driver.

I'm sure, under the wrong set of circumstances, a fire could have happened. I consider myself lucky.
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