So, I will discuss now my work already done on this ICE PSU PCB.

I saw that other members found a blown fuse, and hoped that a replacement will solve the problem. Wrong.

Firstly, it must be understood that this PSU is a Switch-Mode (SMPS) PSU. 

It is NOT a Linear PSU, like the Pre-2000's models sold by B&O.

A SMPS operates at very high frequencies, and reserve voltages are well over 300Volts.

That means that the high frequencies cause very high breakdown rates on the passive components (such as resistors and capacitors), and also the Semiconductors can overheat, if the heat by-product is not managed correctly.

Secondly, when a fuse blows in a SMPS, that means that (beyond all doubt) there is a real and catastrophic problem, usually in the Primary (High-voltage) section of the PSU. 

Throwing more fuses at the PSU is guaranteed to cause only MORE incremental damage.

Before I started work on the PSU PCB, I did a visual inspection to identify any visual clues for defects.

There were no bulged capacitors (but no-bulge is NO guarantee that a capacitor is functional or not), and I was impressed to observe B&O's choice in the components  - Panasonic, Vishay, and ChemiCon - all very high quality.

The only component of which I didn't approve, was the RIFA paper "X2" 220nF supppression capacitor C111 275VAC, especially since the other "X2" cap C113 is a super-high-quality Vishay 339 rated at 310VAC.

In Europe, 310VAC rating is more "forgiving" than a 275VAC rating. Why would B&O have chosen to use the Rifa in one X2 position, instead of installing 2 identical Vishay caps? Maybe lots of Rifa caps in stock? 

These Rifa X2 caps are notorious for exploding and causing all types of damage. After repairing hundreds of Tektronix oscilloscope PSU's, ALL with Rifa X2 explosive damage, I automatically junk these Rifa paper caps whenever I see them installed. They have not stood the test of time.

So, replacing the Rifa paper cap (with the identical Vishay 339 as C113) would be my first recommendation, when looking at a blown fuse. And of course, check for any other collateral damage.

The other visual damage was the cold-solder (cracked) joints on the PCB underside.

Very common on SMPS PSU's, especially with today's unreliable Lead-free solder.

So, I resoldered all the solder joints with Kester 63/37 fully-leaded solder.

I now started measuring all suspect passive components.

The first suspect was R114, a Carbon Composition 1/2W resistor. Carbon Comp resistors do not age well - they absorb humidity, and depart from their specified resistances, sometimes drastically.

This 470R measured over 600 ohms. Predictable, and I replaced it with an new Carbon Comp resistor. 

Carbon Comp resistors are installed for a very good reason - they handle high-frequency pulses better than any other resistor types, and it would be foolish to replace it with any other type.

The next suspects were the electrolytic capacitors.

Normally in SMPS's, the small capacitors fail at a much higher rate than the large units.

So it was here.

The large Vishay, Panasonic FC and Chemicon electrolytics checked perfectly OK on my ESR meter, and there was no need to replace them. Excellent quality, and super-reliable.

Only these electrolytics needed replacing (circled in red):

22uF/50V C514 and C516 

100uF/25V C425, C429 and C611.

I used my gold-standard for SMPS's - Nichicon UPW and UHE.

Subsequent testing proved the SMPS completely functional.

Following this with great interest, as it is nice seeing someone repair some of the newer B&O products - especially as I guess you don't have any schematics to help you? I'm sure this thread will become useful for others in the near future. 

Keep up the good work. 🙂

/Dennis

Thanks for posting! I own a pair of Beolab 9's myself and definitely appreciate seeing some of the issues I may expect down the road.

Before you start to replace all the capacitors, start with identifying the crackling sound. Where does it come from. Just from one driver, or does al the drivers contain that intermittent crackling sound? Crackling noises are never caused by degraded electrolytic capacitors.
From all the defective BL9's I've had, none of them had issues caused by these. 

Beobuddy wrote:

Crackling noises are never caused by degraded electrolytic capacitors.

From all the defective BL9's I've had, none of them had issues caused by these. 

All the electrolytic capacitors have already been replaced.

That's the first order of work - to replace ALL confirmed defective parts.

The crackling is the ONLY problem remaining, therefore you are correct that the capacitors are NOT the cause of the crackling.

The crackling comes from the tweeter.

The tweeters were already swapped in order to determine whether the problem was from the actual tweeter. Not so.

So the first PCB to swap will be the X-over.

My instinct is pushing me in the direction of a cracked SMD solder joint somewhere, but time and further checking will determine whether I am correct.

Have you actually solved any crackling problems on the BL9's?

I’ve solved crackling noises on BL4, 4000(both mk1 and 2), BL1, 3, 5, 7 and 9.

Causes are diverse. 

Menahem Yachad wrote:

That's the first order of work - to replace ALL confirmed defective parts.

You do not know this, unless you desolder all capacitors for a reliable measurement. Even then a measured valid value isn’t a guarantee that it works as it should.