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1983 300CDT, 1994 SL320, 2006 E320 CDI
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Discussion Starter #1
Amplifier problems seem to be a common problem with these R129's. Has anybody opened one up, If so what is usually the problem with them. I have mine out of the 94 SL320, Just wondering what I should be looking for when I take it apart
 

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'95 SL500, '99 ML320, '08 ML550 4MATIC w/Sport & Lighting Pkg, '12 ML350 4MATIC w/P2 Pkg & Pano Roof
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Hi RCF:

The older BOSE amplifiers, manufactured up until the 1989 - 1990 time frame, had electrolytic capacitors that dried up with time, resulting in amp failure.

From 1991 onwards, amplifier failure could be the result of any component. These amplifiers are fairly complex to dismantle and repair oneself.

If you send these units out to be repaired, the "normal" repair cost is ~ $400 USD.

BOSE' Automotive Division in Massachusetts still carries this amplifier in its inventory, and sells it at a clearance price of $250 USD. :D
The amplifier also carries a BOSE 1-year warranty.

I think taking advantage of a new amplifier, at a clearance price, plus included warranty is the way to go. :thumbsup:

You can contact Patty Bolack at BOSE Service Support at:

US Telephone: (800)231-2673
International Tel: (508)766-9522
Fax Number: (508)766-9103

Hope this helps.

God Bless, Arctic
 

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1983 300CDT, 1994 SL320, 2006 E320 CDI
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Discussion Starter #3
Thx, ArticDweller, I took the amp apart looking for bad solder joints or fried components, But didn't see anything obvious and rather than test every part individually I think I'll take your advice and make a call tomorrow to Bose
 

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93 SL500, 95 SL320, 96 S320, 98 S500, 2002 E320 4Matic Wagon & A little 91 5.0 FORD Mustang
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I repaired many amplifiers in my time.

The sound will start to clip, and people may say it gets "staticey".. Basically half of the audio signal in sinusoidal wave is clipped, or the amp may shut down..The amp works for a while and the signal will just disappear..

You want to put in low leakage capacitors, and mail order your capacitors from Mouser Electronics in Texas or Digikey in Minnesota.. They must be fresh because that is the whole purpose. No ebay parts here. Voltage must be the same or larger..The replacement capacitance can be a little larger, but observe the lead spacing and physical dimensions.

The physical large capacitors are the problem 99% of the time. The semiconductor parts never blow up in the Mercedes Amps.

You can fix the amp for less than twenty bucks or so.

Martin
 

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'95 SL500, '99 ML320, '08 ML550 4MATIC w/Sport & Lighting Pkg, '12 ML350 4MATIC w/P2 Pkg & Pano Roof
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I repaired many amplifiers in my time.

The sound will start to clip, and people may say it gets "sticky".. Basically half of the audio signal in sinusoidal wave is clipped, or the amp may shut down..The amp works for a while and the signal will just disappear..

You want to put in low leakage capacitors, and mail order your capacitors from Mouser Electronics in Texas or Digikey in Minnesota.. They must be fresh because that is the whole purpose. No ebay parts here. Voltage must be the same or larger..The replacement capacitance can be a little larger, but observe the lead spacing and physical dimensions.

The physical large capacitors are the problem 99% of the time. The semiconductor parts never blow up in the Mercedes Amps.

You can fix the amp for less than twenty bucks or so.

Martin
Martin:

My amplifier just kept fading out (not clipping) on the sub-woofer channel.
The amp would run the sub-woofer for about 20 seconds, and then fade out to nothing.

In relatively short order, the amp's sub-woofer output channel just stopped functioning altogether.

All other 4 channels worked perfectly.

Wasn't sure what the cause was on the sub-woofer side..... any thoughts?

God Bless, Arctic
 

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93 SL500, 95 SL320, 96 S320, 98 S500, 2002 E320 4Matic Wagon & A little 91 5.0 FORD Mustang
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Your problem is the channel with bass, and it is either a feed capacitor, or the output capacitor...

I'm might be able to help you,

I need a pin-out of the connection to your amp, or give me a link where I can download one..

I can then look on my amp, and tell you where the capacitor is at.

Martin
 

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'95 SL500, '99 ML320, '08 ML550 4MATIC w/Sport & Lighting Pkg, '12 ML350 4MATIC w/P2 Pkg & Pano Roof
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Hi Martin:

Thank you so much for offering to help me on this amp fix.

I'm away at the moment, but will PM you when I get back next week.

Until then, God Bless, Arctic
 

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93 SL500, 95 SL320, 96 S320, 98 S500, 2002 E320 4Matic Wagon & A little 91 5.0 FORD Mustang
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Okay Artic,

1995 was the year Mercedes Amps had more parts inside.. I'm not sure if the design changed in 99. I believe it did as Mercedes reduced the parts count-Increased reliability, lowered cost, and lowered fidelity. Each of the internal amps inside are identical inside as W140 internal amps of 1995, and 1996 to 1999. The W140 amp is cheaper, and uses integrated outputs versus discrete transistor output stages, so I think you will encounter the same in your 1999. Here on the 1995 amp each internal amp has its own capacitors, yet the later ones share the large capacitors.

On the 1995 amp you will need to remove all the external Torx T15 screws, and the piece of hook and loop tape needs to be peeled from the aluminum heat sink portion, yet after the screws are removed the end plate without the connector will fall-out.
 

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Next, Is to pry the bottom plate out. It will pivot on the other edge. Two slot openings are there to pry it open with a flat screw driver. Once the bottom plate pops up. Pivot it open slowly towards the other edge. Open the bottom, so it looks like the forth picture.

The transistor hold-down silver plates have to pried. The are hard, and the edges are sharp, so do not get your finger cut their. This amp has four internal discreet amps, sot it will have four of these hold down, but other generations may have less than what is pictured. Once the hold-downs are removed the circuit board will separate from the aluminum heat sink. Try not to cycle the ribbon cables as it may break at the terminal portion.
 

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The third from the large terminal is the bass channel, and the amp section next to the relay is the one responsible for the Bass channel. If your internal parts to your amp are identical to my amp then it is the two brown electrolytic capacitors are at fault. The capacitors just dry up, and no longer filter or provide temporary energy storage.

The Capacitor is 820uF at 16v The Temperature is 105c, the Grade is PL(which is no longer made, but I have a conversion chart), The size is critical, but more for lead spacing as it needs to fit on the circuit board.

The Diameter is 10 mm
Length is 25 mm
Lead spacing is 5.5 mm

I buy most of my raw electronic components from Mouser Electronics in Texas. NO EBAY OR CRAGLIST deals. The WHOLE purpose of buying REPLACEMENT capacitors is to buy the freshest ones, and NOT to try to find the OLD PL grade as it has been superseded by a higher performance capacitors. 99% percent of the times these brown capacitors are found on a circuit board the capacitor grade must be looked-up. Consequently, the wrong type replacement can lead to failure or explosion, so looking up the PL grade on the PDF chart(and by the way the capacitor is made by Nichicon). The replacement for PL is PM grade.

On the Mouser website:

Mouser Electronics - Electronic Components Distributor

Go to Passive components on the right.

Select:

Capacitors
Aluminum Electrolytic
Aluminum Electrolytic-Leaded

You will get to a page like this:

Aluminum Electrolytic Capacitors | Mouser

On this page, The manufacture is selected(Nichicon), The capacitance is selected(Mine are 820uf), and The voltage of the capacitor(mine are 16v). Then hit the button Apply Filter, and you get this page:

Aluminum Electrolytic Capacitors - Leaded | Mouser

A list of capacitors will appear, and look at the Mouser part number. Look at the trailing letters-MCL, MPD, MHD, MNL, and etc.... Our grade we are after is MPD-written backwards-PM... If you are unsure, just click on the data sheet hyperlink, and at the top it will say what grade it is:

http://nichicon-us.com/english/products/pdfs/e-pm.pdf

Next thing to watch out for is the dimensions. That is why I took measurements as the circuit board space is restricted, and the wrong lead spacing will just not fit on the board, so look off to the right on the selector guide on the right to match-up the dimensions and for my large capacitors it was this:

UPM1C821MPD Nichicon | Mouser

Only the very large capacitors should be replaced. All the little ones will be fine for the next 20 or so years... I would replace all the large ones, and on my amp I have eight capacitors. Always replace them in pairs!!!.. Notice, the white/gray band on the capacitor facing outward. That strip or dash is referencing the negative lead of the capacitor. When the new ones are installed. The stripped end must be in the same direction, or else a nice firecracker explosion will occur.. Watch out for the polarity!!!

I'll let you in on my secrets....I do not bother to test these as if one failed the others will fail soon-no comebacks-Got to protect my reputation:D

Yes, it is a pain in the butt to do this, but I'm a person of no pain-no gain...I do it all, and this is my trade...I feel right at home...:)

DO NOT replace these capacitors with a SOLDERING GUN:

D650 - Weller - Apex Tool Group 300/200 WATTS, 120V INDUSTRIAL SOLDERING GUN

This is not the tool as it emits a voltage, and will ruin the other components. You need a soldering iron or soldering station with a standard tip(no blade tips) in the wattage of 35 to 45watts of power.

I know their is piles of youtubes on how to desolder and solder...

The simplest way to desolder the old capacitors is to use desoldering(solder wick as it may be called) braid with rosin(flux in it). Do not use this No-clean stuff. It is just a royal pain to use. The width should be 2mm to 3mm in width, so it is easy to work with..A small service spool is all that is needed. Remember to apply a little solder to the tip of the soldering iron, so transfer the heat to the braid, or it will not wick-up the solder.

Amazon.com: solder wick

Hope it helps,

Martin

Now my plug, if anyone needs their amp fixed/rebuilt in the USA here, I can fix this one for the R129, W210 or 2nd generation W140 for a $140 bucks with return freight included...
 

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Tough to tell for sure, but a couple of those electrolytic caps appear to be slightly swollen - a good indicator that they're failing or about to fail.

You should be able to replace all the electrolytics for under $20 from the looks of things.

Keep us posted.

Dan
 

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Dan,

From the pictures yes it is hard to tell if they are swollen, but because these amps have limited use. They will rarely swell. Most modern capacitors will just vent, but not swell. Unless it is in a high heat environment, wet environment, or a high use environment..

The Large capacitors are the ones responsible for all the problems in these amps.

Martin
 

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Hi Martin:

Thank You 1,000+ times for your write-up on how to DIY repair on the BOSE Amplifier. :bowdown::bowdown::bowdown:

I disassembled the amp, and it was identical to the one in your pictures. Capacitors were the same 820 uf and 16v, too.

I ordered 8 new capacitors, to do the entire board, from Mouser Electronics.

Price was $9.04 USD for the 8 caps, plus $8.00 for USPS Global Priority Shipping, for a total of $17.04. :thumbsup:

I just need to get some braided wire wick to uptake the old solder, and I'm good-to-go. I have a solder pen for the R&R.

I really think your write-up is so good, it should be posted on the Blue STICKIES.


Last question on this: Any tips on how to remove those globs of glue that are in between the capacitors and the coils? :eek:


God Bless you for your help in all this, Arctic
 

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Thank you Arctic,

Just trying to share the knowledge..

To remove the "Hot glue" blobs I pinch and grab them with standard needle nose pliers, and at times use the ultimate tool of the flat blade screw driver to pry them out.

Most amps have them, but I have encountered a few amps not having the glue.

Martin
 

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I too, had amp problems - however, mine were of the 'sizzle/whine' variety coming from the front, passenger speaker. I thought maybe the 8 'big' capacitors mentioned in the previous posts were the culprit, so I ordered them from Mouser Electronics and replaced them. Still had the problem. So, I cracked the amp case back open and decided to replace the remaining caps on the main board - and ordered the following from Mouser Electronics (16 in total) - two 25v-100uf (647-JVZ1E101MED), four 50v-1uf (647-UST1H010MDD), and ten 16v-10uf (647-UMT1C100MDD). The ten 16v-10uf didn't exactly match the size of the previous ones (they were a bit shorter), but the specs were the same. Hopefully that won't be a problem down the road.

If you're going to take the time and try to fix your amp, I really suggest replacing ALL of the caps (on the main board) at the same time. It's not that much more work, and you'll save yourself on postage (and order/delivery time) by only having to order once instead of twice! I think it took about 3-4 hours (taking my time) to complete the job. Warning: it can be a 'challenge' to locate the back side of the capacitor when removing it, due to all of the other small components - some boards have the components marked on both sides....not these!

Anyway, it was a fun project, and after replacing all of the remaining caps, I now have a working amp again, yeah!!!!
 

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1994 E420
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I attempted this repair, but haven't been able to fix the amp. I was getting cracking/popping from the driver door speaker, as well as muddy base from the subwoofer. After desoldering and replacing the big caps with the recommended fresh ones from Mouser and reinstalling the amp, I now have no sound at all.

Is there a way that I can test pins on the amp with a multimeter to see if and where it failed? Is there anything else I should check? I have checked the fuse on the amp and it is OK.

Thanks in advance.
 

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1998 Pano SL500; 1993 SL500; 2005 ML270cdi
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I attempted this repair, but haven't been able to fix the amp. I was getting cracking/popping from the driver door speaker, as well as muddy base from the subwoofer. After desoldering and replacing the big caps with the recommended fresh ones from Mouser and reinstalling the amp, I now have no sound at all.

Is there a way that I can test pins on the amp with a multimeter to see if and where it failed? Is there anything else I should check? I have checked the fuse on the amp and it is OK.

Thanks in advance.
Remember with electrolytic caps that they can only be fitted one way. Each cap will have a series of negative symbols on one side. Usually the circuit board will show how the cap should be fitted with half of the area coloured black or with lines.
 

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1998 Pano SL500; 1993 SL500; 2005 ML270cdi
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To remove the "Hot glue" blobs I pinch and grab them with standard needle nose pliers, and at times use the ultimate tool of the flat blade screw driver to pry them out.

Most amps have them, but I have encountered a few amps not having the glue.

Martin
I've just repaired a power supply board to a smart battery charger. Not only were there blobs of glue between components, but the caps were actually stuck to the circuit board with a white adhesive!!

To remove components I always use a suction tool for molten solder around the component legs, I can then just lift out the components with my fingers.
 
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