My BK XXLS400 developed a hum…

Raymond Lin · 20 May 2023 at 12:04

No idea what happened, watching a movie and after a loud section in a movie I started hearing a weird hum from the sub, I’ve disconnected all the wires and it is still present.

Doing a bit of reading it sounds like it could be either a transformer hum or a dead capacitor or solder joint…

I got it like 15+ years ago so way out of warranty and honestly with its weight, not sure how I could send it back for repair. I have emailed BK to see what they say anyhow.

What would you guys do? And anyone have experience of this here?

Begbie · 20 May 2023 at 12:08

If it was broke, out of warranty, and cost too much for a repair. I'd try and find the diagrams and strip it apart. Probably only a small board anyway, so probably easy to work out?

Or find a local electronics technician, local audio shop?

hornetstinger · 20 May 2023 at 12:41

Hum probably be the large capacitors, common fault with BK but easily replacable.

Raymond Lin · 20 May 2023 at 12:56

Begbie said:
If it was broke, out of warranty, and cost too much for a repair. I'd try and find the diagrams and strip it apart. Probably only a small board anyway, so probably easy to work out?

Or find a local electronics technician, local audio shop?

I guess calling a local place can’t hurt. If it’s a capacitor then it’ll be cheap, if it’s a new transformer then I might have to get a new one…

hornetstinger · 20 May 2023 at 13:14

I recall BK charge £75 for repair that includes shipping

Don't need to send whole sub back just plate amp. Although it just happened to fail on loud part so I'd probably want the driver tested maybe you blew the driver?

Raymond Lin · 20 May 2023 at 13:26

hornetstinger said:
I recall BK charge £75 for repair that includes shipping

Don't need to send whole sub back just plate amp. Although it just happened to fail on loud part so I'd probably want the driver tested maybe you blew the driver?

I don’t think so as it wasn’t that loud as I was watching a film at 11pm.

I also noticed that it hasn’t sounded the same for a while, I thought it was the new Denon I got last year but it had felt off since. But the hum is a new development.

I will call BK on Monday in person to see what they say first I think. I think anyhing under £250 would be justifiable to repair it vs the cost of a new one.

hornetstinger · 20 May 2023 at 13:37

Raymond Lin said:
I don’t think so as it wasn’t that loud as I was watching a film at 11pm.

I also noticed that it hasn’t sounded the same for a while, I thought it was the new Denon I got last year but it had felt off since. But the hum is a new development.

I will call BK on Monday in person to see what they say first I think. I think a thing under £250 would be justifiable to repair it vs the cost of a new one.

A new plate amp would probably be around £250.

Or just buy a new sub ;-)

or four

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Raymond Lin · 24 May 2023 at 20:47

BK got back to me, sent me instruction of how to take it out, pretty easy.

I can't see any burnt caps.

Although I notice the sub isn't doing anything, I unplugged the Anti-mode and ran just the IC cable to the sub did a Audessy test...i thought i felt the sub move but when watching a movie I could not feel any low frequency...

hornetstinger · 24 May 2023 at 20:51

I believe it's the big caps when replaced fix it. Quite a common issue with BK, but at least affordable and done by any decent electronics repair shop...or DIY.

theone8181 · 25 May 2023 at 06:05

I'd imagine if one of those caps went, it would have been a bit of a bang

.

Begbie · 25 May 2023 at 06:15

theone8181 said:
I'd imagine if one of those caps went, it would have been a bit of a bang .

Maybe, I've seen bigger capacitors go and still look fine.

Raymond Lin · 25 May 2023 at 10:47

Packing it up is a challenge I must say!

Raymond Lin · 31 May 2023 at 10:49

Update.

"A faulty high voltage power supply capacitor would have been the cause of the humming, but the amplifier hardly had any signal output and that's why you lost bass, this is caused by the capacitors on the low voltage supply. Both sets have been replaced and the amplifier is working, it will be passed onto another engineer to check the first engineers work and he will final test it."

Total cost £55 which includes VAT and shipping!

Minstadave · 31 May 2023 at 10:54

Raymond Lin said:
Update.

"A faulty high voltage power supply capacitor would have been the cause of the humming, but the amplifier hardly had any signal output and that's why you lost bass, this is caused by the capacitors on the low voltage supply. Both sets have been replaced and the amplifier is working, it will be passed onto another engineer to check the first engineers work and he will final test it."

Total cost £55 which includes VAT and shipping!

That's a good service.

theone8181 · 31 May 2023 at 13:39

That's bargainous imo, you'd struggle to get a sub for 55 quid, even used.

hornetstinger · 31 May 2023 at 14:22

Raymond Lin said:
Update.

"A faulty high voltage power supply capacitor would have been the cause of the humming, but the amplifier hardly had any signal output and that's why you lost bass, this is caused by the capacitors on the low voltage supply. Both sets have been replaced and the amplifier is working, it will be passed onto another engineer to check the first engineers work and he will final test it."

Total cost £55 which includes VAT and shipping!

Yeah that's one thing I like about class AB sub plate amps. Fixable for reasonble price.

Try doing repair on a Velodyne DD 18+ plate amp or similar...

NickK · 14 Jun 2023 at 12:57

So sudden hum is typically either:
* PSU caps have died or below performance required
* diode failed - so a full rectification is now half (ie half energy causing more ripple and thus hum)

It could be further along the power supply or semiconductors but start with power first.

Ahh see you have it sorted

413x · 24 Jun 2023 at 18:27

Raymond Lin said:
Update.

"A faulty high voltage power supply capacitor would have been the cause of the humming, but the amplifier hardly had any signal output and that's why you lost bass, this is caused by the capacitors on the low voltage supply. Both sets have been replaced and the amplifier is working, it will be passed onto another engineer to check the first engineers work and he will final test it."

Total cost £55 which includes VAT and shipping!

Do you have instructions/details on this?

My xxls is also not working properly (kind of constant buzz)

Particularly how to get it apart?

Raymond Lin · 24 Jun 2023 at 18:44

413x said:
Do you have instructions/details on this?

My xxls is also not working properly (kind of constant buzz)

Particularly how to get it apart?

This was the link they sent me

Opening an XLS200-DF

How to open an XLS200-DF

youtu.be

When detaching the cable from the PCB to the speaker, mark which one is positive and negative so you know when you put it back together.

413x · 24 Jun 2023 at 19:45

I'm pretty sure I don't have that cable anywhere he used to pull it open