the dreaded Boston acoustic VR2000 sub woofer hum

[rapidrepair]

has anyone found the cure for the Boston acoustic VR2000 sub woofer hum all caps and surrounding components have been change and the line in has been disconnected from the power amp board and the unit is still humming i need a schematic so i can check the feedback circuit can anyone help or have any solutions for this problem

 

[Inductor]

Try to keep it away from Multi Socket Extensions and other RF interferences and check.
Does it have a "earth" / "safety ground" wire or connection? or is it just a 2 pole socket.
What colour wire goes to positive on an electrical plug

Also read here ""And there is hum from the amp which can only be heard if the room is dead quiet, but what do you expect from a 325 watt amp.""
Boston Acoustics VR 2000 Floorstanding Speakers Reviews

I also found this problem in a variety of subs, with relation to environment/connections or maybe the type of amps used (class-D amplifier or switching amplifier) I don't know, but I had a problem with one at home and it was working fine at the shop with balanced connections and all. A very naughty sub...

 

[islandman]

hum problem

I had the same problem with hum. I have two VR2000 subs and one developed a hum. I called Boston Acoustics and they said to mail them the amp panel and that they could repair it. Ii has been at least 5 years since the repair and still no hum. Great customer service from Boston.

 

[VidTech]

I had an issue with my VR2000 sub a few weeks ago. Maybe this will help others with this type of failure.

Symptom:
Amplifier hums when on. Input is irrelevant. Volume control affect hum level slightly.

Diagnosis:
Regulated negative 12 volt supply developed about 1 volt p/p, 60/120 hz sawtooth wave riding on the DC voltage. This power supply is the negative portion of a bipolar supply, which supplies a stable voltage to the filter networks, input buffers, etc. Input and output caps replaced for the negative 12 volt regulator. Measurement of capacitor indicated original main input filter cap(C13) measured 25% lower than design spec.

Repair:
The negative rail is the actual culprit in this case(C13 and C17), but due to the age, the positive side was also replaced(C18 and C19).

Normally the main filter caps are suspect when dealing with long service linear supplies. These were changed as "routine maintenance"; these components have been in service 24/7 for at least 12 years.

Also, under temperature and current extremes, I have seen these regulators get unstable. However, I haven't seen this symptom exhibited. That said, if I would have had one in my parts box, I would have swapped it out while I had the opportunity because of its age.

DIY tip: Use a permanent marker to mark polarity for the caps. Replace the caps with the same polarity. If reversed, they will fail and possibly explode. Also due to the type and design of this power supply a higher value can be used for C13 & C18. I used a 1000 ufd @ 25 volt cap.

Parts List:
C17, C19 - 100 ufd @ 16 vdc radial electrolytic capacitor
C13, C18 - 470ufd to [email protected] 25 volt radial electrolytic capacitor
U2 - LM7912 3 pin negative 12 volt regulator
U3 - LM7812 3 pin positive 12 volt regulator

 

[dayna]

VidTech,

I am interested to know if you know what the difference between the 240V and 120V version of the VR2000 unit. Usually it is the caps in series vs parallel? or something.

Any how I am in NZ which we are 240V, and I already have a VR2000, but am looking at importing one from the US, which is obviously built to run 120Volt.

I should be able just to compare differences and adjust accordingly, but just interested in any heads up advice or knowledge of this.

Also my unit does exhibit a small hum, but never bothered me enough to fix it. If its on, its making bass.

Fantastic subs ...

 

[Khron]

More likely, the 120v vs. 230/240v versions either have different transformers, or (the better/easier/cheaper version), the transformer has a dual primary winding. For 115/120v, they're in parallel; for 230/240v they're in series

 

[dayna]

I took mine apart to look and the transformer has at least 4 wires coming off to the power, 2 wires are joined together in the screw block but not going anywhere (effectively in a loop), and the other 2 go to the mains power respectively . So maybe that transformer has the wiring configured differently for the 120V version, lets hope, will be interesting. Thats if i get this speaker....

I just received some EV powered PA speakers from the US, and they had 120V on the sticker, took the amp out and there was a jumper plug that ya pulled for 240V operation, simple as pie!

PS: I appreciate the reply, thanks for your time.

 

[Khron]

Manufacturer cost-cutting CAN occasionally have positive sides too Just too bad that's not always the case

 

[mboncaldo]

THANKS VidTech!!!!

I had an issue with my VR2000 sub a few weeks ago. Maybe this will help others with this type of failure.

VidTech-
Thanks so much for this excellent information! It is exactly the symptom I had, and replacing the components exactly as you described (2 voltage regulators and 4 caps) fixed the problem!

Your concise professional explanation of the problem and solution saved me who knows how many hours (or weeks...) it would have taken to diagnose myself.

I have to say, if all information on the web was of this high quality, all of humanity would be seriously elevated.

 

[flacoman]

Why does my subwoofer hum ? Because it doesn't know the words!

 

[Shadydave]

LM78XX and LM79XX regulators like to go into oscillation.
If you put a 10 - 47 mfd electrolytic and a 0.01 mfd Tantalum between output and ground they always calm down.
The Tantalum is important and if oscillation is happening it takes a large electrolytic without the Tantalum.
In my experience.

Best of luck to anyone doing repairs,
Dave

 

[burmeister]

Boston acoustics v2000 humming

I know this is quiet an old post but I would like to say thanks a lot for your help.....got this sub very cheap and had the same problem.....just followed your advise and it worked out very well.....now, I have dual sub, with paradigm reference sub15.....both bought in Friday market.......

I had an issue with my VR2000 sub a few weeks ago. Maybe this will help others with this type of failure.

Symptom:
Amplifier hums when on. Input is irrelevant. Volume control affect hum level slightly.

Diagnosis:
Regulated negative 12 volt supply developed about 1 volt p/p, 60/120 hz sawtooth wave riding on the DC voltage. This power supply is the negative portion of a bipolar supply, which supplies a stable voltage to the filter networks, input buffers, etc. Input and output caps replaced for the negative 12 volt regulator. Measurement of capacitor indicated original main input filter cap(C13) measured 25% lower than design spec.

Repair:
The negative rail is the actual culprit in this case(C13 and C17), but due to the age, the positive side was also replaced(C18 and C19).

Normally the main filter caps are suspect when dealing with long service linear supplies. These were changed as "routine maintenance"; these components have been in service 24/7 for at least 12 years.

Also, under temperature and current extremes, I have seen these regulators get unstable. However, I haven't seen this symptom exhibited. That said, if I would have had one in my parts box, I would have swapped it out while I had the opportunity because of its age.

DIY tip: Use a permanent marker to mark polarity for the caps. Replace the caps with the same polarity. If reversed, they will fail and possibly explode. Also due to the type and design of this power supply a higher value can be used for C13 & C18. I used a 1000 ufd @ 25 volt cap.

Parts List:
C17, C19 - 100 ufd @ 16 vdc radial electrolytic capacitor
C13, C18 - 470ufd to [email protected] 25 volt radial electrolytic capacitor
U2 - LM7912 3 pin negative 12 volt regulator
U3 - LM7812 3 pin positive 12 volt regulator

 

[skyhouse71]

I am having this same problem and have found this thread to be a great help. However, if anyone is still monitoring this thread, how do you get the circuit board out in order to replace the parts? My board is covered with a grey, rubber like cement and I think i may have to take apart the binding posts in order to get the circuit board off but I don't know how to do that. Can anyone help with that?

 

[skyhouse71]

dont know if anyone is reading this but:

I was able to get the board to separate from the rubber cement but now that I can see all the parts, the U2 and U3 on my board are 8 pin op amps JRC 4558DD. How to you replace those with a 3pin voltage regulator? very confused. Unless I have some design that is different.

 

[JonSnell Electronic]

Obviously you have a different design release. The 4558's are dual pre amps and the 3pin LM's are voltage regulators. Manufacturers as they change factories, change their designs. Have you got a service manual? Is yours Class D with a switch mode power supply?

 

[skyhouse71]

Thanks for the reply. I emailed Boston Acoustics last week for the service manual but they said they don't have any they only gave them to there service techs. So unless you guys know of another place to get them I am SOL. Would there be something on the circuit boards?

 

[Mad A]

I have the same sub with the same hum so I will go ahead and try replacing the C13 and C17 capacitors as mentioned earlier, and maybe the other two while I am at it.

I am a complete newbie when it comes to this, but I learn quickly with the help of the internet and youtube videos

Can anyone guide me to a link to the proper capacitors I need to buy? Looking to get the ones mentioned below. I tried searching through some websites and was a bit overwhelmed with the options.

C17, C19 - 100 ufd @ 16 vdc radial electrolytic capacitor
C13, C18 - 470ufd to [email protected] 25 volt radial electrolytic capacitor

 

[Absoulution]

I am having the same problem with this sub. I removed the sub from the box, trying to remove the amp from the enclosure. I removed the screws from the heat sink, but it's still attached.

I would greatly appreciate any help with getting the sub back in operation. It's a wonderful speaker outside of that annoying buzzing/ humming noise!

 

[ouimetnick]

If you are certain that all of the screws are removed, then push it out through the hole in the front (woofer removed)

Be careful as there is a cable, and power cord connecting the control panel to the big amplifier heatsink. The heatsink is also VERY heavy because of the big transformer bolted on. Just be careful that nothing falls out damaging the fragile connections.

 

[Absoulution]

If you are certain that all of the screws are removed, then push it out through the hole in the front (woofer removed)

Be careful as there is a cable, and power cord connecting the control panel to the big amplifier heatsink. The heatsink is also VERY heavy because of the big transformer bolted on. Just be careful that nothing falls out damaging the fragile connections.

Thank You! Thank You! That did the trick.
Hoping these component's will bring her back.

Parts List:
C17, C19 - 100 ufd @ 16 vdc radial electrolytic capacitor
C13, C18 - 470ufd to [email protected] 25 volt radial electrolytic capacitor
U2 - LM7912 3 pin negative 12 volt regulator
U3 - LM7812 3 pin positive 12 volt regulator