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Old 6th December 2014, 03:41 PM   #1
Hayden is offline Hayden  Australia
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Default Bad capacitors. Bad design or bad caps?

I have a Denon DN-X1500 mixer and the output was a little crackling, I have noticed that 4 out of about 50 capacitors are bulging on that one board so I was going to replace them.

Question: Do you think I should replace them all? Or replace all the caps in the area of the bulging ones? Or just replace the faulty ones?

Question: is it due to faulty caps or bad circuit design causing them to malfunction? How do I know this?

Oh and also the mixer does get quite warm in use BUT I donít think it means itís faulty as itís a common thing with those models meaning itís just what they do. (bad design maybe causing them to fail prematurely)
The faulty caps are SMG 35v 100uf which only 4 are bulging out of about 8 on that board but the rest could be in a different circuit.
I have attached a photo of the board, about 99% of the capacitors are the one brand SMG I hope this brand is a reliable component because the boards are riddled of them

The capacitors with the red dots are the bulging ones and the ones I have circled are the same value as the bulging ones.

Any thoughts are greatly appreciated!! Thankyou
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Old 6th December 2014, 03:50 PM   #2
rayma is offline rayma  United States
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Definitely replace at least these bad electrolytic capacitors, you'll be glad you did. All of them, if possible.

For longer life use a higher voltage rating and a higher temperature rating than the originals.

Last edited by rayma; 6th December 2014 at 03:54 PM.
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Old 6th December 2014, 04:28 PM   #3
kevinkr is offline kevinkr  United States
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Are those the line output capacitors? (Or supply bypass?) Might want to check what the mixer board is plugged into as well.

Also make sure that the output circuits are not oscillating as internal heating in the caps due to oscillation could cause this.
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Old 6th December 2014, 05:10 PM   #4
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At a minimum i would replace all the capacitors of the same value. Depending on how much the mixer is worth to you i would consider doing them all.
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Old 6th December 2014, 05:49 PM   #5
Eldam is offline Eldam  France
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how is the sound (not talking of the crisp) with smg caps : soft, not soft ?

can dictate what ref to us near the aop...

If me I would change asap the caps of the powersupply by some Panasonic FR e.g. , any 105įc or Long Life firstly. Then change the faulty caps only as sometimes digital circuits could be damaged by EMC or too much heat from the soldering iron. Forgett what I write if you are already skilly !

try some bipolar or Elna Silmic 2 in the signal path to swap the output DC caps.

For the OAPs : stay with electrolytics with the ones you like or find. cheap Panasonic or Nichicon e.g.

maybe forn the digital chips you would not have trouble with polymers :UCC APSA serie or Panasonic polymer SEP serie (SEPC could be a little too tighty and give strange results, better to avoid them for a simple swap as you plan).

i will have a look on datasheet to look at the leads pitch as size of the cans to avoid surprises and of course with the same capacitance & voltage values.
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Old 6th December 2014, 05:58 PM   #6
Mooly is online now Mooly  United Kingdom
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Its very strange to see low voltage circuitry with bulging caps.

I would measure the voltage across them and confirm its OK (are the four caps in parallel). Polarity OK... it happens

Next up would be to scope across them and see if there is any excess ripple of any kind present. If so then that would point to a power supply problem further forward in the chain.
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Old 6th December 2014, 11:30 PM   #7
dangus is offline dangus  Canada
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Heat has been a contributing cause of every bad cap that I've encountered, very often so much heat that the board is discoloured. (Except for one little coupling cap in a Pioneer receiver that I fixed in the late '80s.)

Maybe remove one suspect capacitor and measure it. Bad caps (not surprisingly) IME will measure very bad, usually a fraction of the normal capacitance. It's amazing that switching power supplies can keep on working up until the last gasp of the caps.

Crackling in the output might be something else, like bad pots or intermittent connections.

Last edited by dangus; 6th December 2014 at 11:37 PM.
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Old 9th December 2014, 11:54 AM   #8
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the 1500 is a unit from 2004, and more or less , the denon with the first use of a
cpu on a larger scale , but besides the first year and some updates (faders worked terrble at first with the cpu and perfect after an update). Offcourse followed by the very well build x-1600 and x-1700. And i have the x1600 and at the moment i still don't know a better unit , which is traktor certified , and that quality soundcard and options.But those to came in 2009 on the market and denon owned marantz and had a large portion in allen and heath, so know how a lot.

The 1500 is, believing, the reviews, after the updates a good working and well sounding unit and made for years. A crispy sound , with a clean low etc. , but
component wise i only know the x-1600, cause i own one myself. And after eleven years it ain't a shame a cap breaks down. It's not a problem unit, which i think the pioneer turntable will be...

Greetings richard

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Old 9th December 2014, 09:46 PM   #9
irribeo is online now irribeo  Netherlands
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Nippon Chemi-Con SMG

(and maybe check connector and cap there)
Attached Images
File Type: jpg smg.jpg (477.9 KB, 65 views)

Last edited by irribeo; 9th December 2014 at 09:59 PM.
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Old 10th December 2014, 07:38 AM   #10
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I tried to find a schematic for the Denon DN-X1500, but no luck. So, my comments are generic. If someone could post one, or a link, we can get to the nitty gritty much more easily.

Not sure if I'm reading the date codes right, but the parts on the PCB generally seem to be from 2006, and the good part is that electrolytic capacitors are better now than back then, especially if you're willing to pay for the current 'nice' versions.

Look for caps that are rated for 105 degree C, and also rated for long life (5000 or more hours). It's helpful to know the function of the capacitor, as there is a tradeoff between low leakage and low impedance. In other words, a coupling cap needs low leakage, and only 'normal' impedance, but a bypass cap needs low impedance, possibly at the expense of extra leakage, which is not so important there.

Those are the two main applications of el-caps, so if you can figure out what those bulging caps were supposed to do, you can pick modern versions that will last a very long time and probably perform better as well. I tried to read the chip markings near the bulging caps to determine the function of the ICs they were next to, but it was sorta tough, so try to find a schematic and report back?

Another good idea is to find a replacement for each type of cap that is bulging, and replace all caps on the board of that same type. It's likely that all of those caps will fail similarly, either due to a problem with that lot of caps, or to a design issue, so you might as well fix them all right now.

Not sure which caps to suggest, but Panasonic has been making a wide range of very high quality electrolytics, and their current 'nice' caps are pretty amazing, offering high temperature tolerance and extremely long life. For example the FR series offers 5000 to 10000 hour life, very low impedance and relatively low leakage. You could probably just use FR series for those caps, regardless of their purpose, and probably do well.
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