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Beomaster 1900 Humming

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SantaCruzTV
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SantaCruzTV posted on Wed, Oct 12 2016 8:39 PM

Hi there, first time posting here, but I've been repairing audio / video equipment for 30 years.  I don't see a lot of B&O products, but I'm trying to fix one for a good customer.  He bought a Beomaster 1900 off eBay that supposedly worked.  But, it has a hum that is present behind the audio and increases as you increase the volume.  The main filter cap (I believe must have been a can style) has been replaced with a 10,000uf / 35v and a 1000uf / 35v (looks like recent work).  I can't rule these out as the cause, but I thought I'd check in here first to see if anyone has any experience with this sort of failure.  I'm not really looking to re-cap the whole unit as that might be cost prohibitive.  Any thoughts would be greatly appreciated.

Best Regards,

Greg

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Dillen
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Answered (Not Verified) Dillen replied on Wed, Oct 12 2016 9:51 PM
Suggested by jegy

SantaCruzTV:

The main filter cap (I believe must have been a can style) has been replaced with a 10,000uf / 35v and a 1000uf / 35v
I'm not really looking to re-cap the whole unit as that might be cost prohibitive.  Any thoughts would be greatly appreciated.

Greg

The main filter caps should be 4700uF or 5000uF 50V. That's one for the positive and one for the negative supply for the amplifier.
They should be identical.

On the main board you'll find an axial 2200uF filter capacitor for the low voltage supply.

Humming could be caused by many things. Aging capacitors is by far the most common reason - and curiously it's usually not the large
power supply filter caps causing this problem but typically some of the smaller ones.
Fair to say that all Beomaster 1900/2400 will benefit from having the old electrolytic caps replaced by now.
They will all be - if not bad then at least marginal.
A bad rectifier could also cause humming, as could wrong wattage frontpanel lamps.

Caps and lamps kits exists.
In my opinion, if the Beomaster is in fair condition in other respects, it's worth grabbing a kit and get to work.

Martin

SantaCruzTV
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Hi Martin, thank you for the reply.  I've attached a picture of how the unit looked when I opened it up. Someone previously had wired these capacitors in the back of the unit under the speaker terminals.  One is 10,000uf / 35v and the other is 1000uf / 35v.  I'm not seeing a 4700 or 5000uf capacitor in the unit, so I'm guessing these were installed instead? Not sure why he wouldn't have just used the correct values???  I found the schematics, but was hoping to find a wiring diagram to make sense of the way these caps are wired?  I understand about the benefits of re-capping the whole unit, but I'm a little leery about the previous repair attempt and what else might have been done to it.  Should I start with replacing those two caps with 4700uf / 50v and go from there?  The physical condition of the unit is pretty nice, and my customer really likes these units as he has now bought two of them off eBay.  Unfortunately each one has problems.... the other is blowing fuses.

Thanks again,

Greg


Dillen
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Dillen replied on Thu, Oct 13 2016 7:22 AM

What a mess.
Yes, replace those two with 2x 4700uF 50V.
They are in series with thieir common pin at ground.
That makes a negative pin from one cap for the negative supply and one positive pin from the other cap for the positive supply.
Just as any other dual supply.

Email me for kits if needed.

Martin

SantaCruzTV
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Hi Martin, Thank you for your replies.  I'll start with those two caps and consider the capacitor kits if I'm still having problems, or if the customer wants to go for a full restoration. 

 

Best Regards,

Greg

LarryD
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LarryD replied on Fri, Oct 28 2016 8:14 PM

Hi Martin,  I am  the customer in question on this thread.  yes,  we'd like to get the cap and lamp kits.  I can't figure out where/how to email you.   

 

Thanks for your help !  Larry 

LarryD
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LarryD replied on Fri, Oct 28 2016 8:14 PM

Hi Martin,  I am  the customer in question on this thread.  yes,  we'd like to get the cap and lamp kits.  I can't figure out where/how to email you.   

 

Thanks for your help !  Larry 

Dillen
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Dillen replied on Sat, Oct 29 2016 8:23 AM

Larry, I sent you an email.

Martin

philgeek
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philgeek replied on Tue, Dec 18 2018 10:06 AM

Hi friends

Let's introduce myself. I'm about 60 years old, Parkinson disabled ... and HiFi belover. I've bought a Beomaster 1900-2 and I would try to revise it by myself. I think I've to recap & change some lamps. Where could I buy repair capacitance & lamps repair kits and get instructions / tutorials ? Thank you in advance. I like this forum which allows so beautiful audio equipment to get chance for a second life ...

jegy
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jegy replied on Sun, May 26 2019 5:34 PM

Hi, I am repairing a Beomaster 1900 that is humming. I have a couple of questions accordingly:

- Did you get rid of the hum?

- Did you replace all capacitors?

- Did you find the bad one or were there more defective?

- Could you connect me to the capacitor kit supplier?

 

Thanks in advance

Best regards

Jens

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