BeoGram

Re: Beogram 800 hum problem

Piaf — Fri, 26 Feb 2010 00:50:48 GMT

Hi Martin,

Thanks for the information.

The Beogram 8000 is performing in an outstanding manner thanks entirely to you and your workmanship on the motherboard.

This hum only occurs when starting up, so no problem….

Jeff

Re: Beogram 800 hum problem

Dillen — Thu, 25 Feb 2010 07:47:42 GMT

Adam, it could be a fault in your Beomaster.
It's not uncommon to see cracked solder joints in the connector bay and where the vertical connector board
meet up with the horizontal.
It won't take much lack of grounding to cause hum, but it could also be a fault in the preamp or power supply.

Martin

Re: Beogram 800 hum problem

kimberley — Thu, 25 Feb 2010 07:18:05 GMT

My Beogram 8002 has a similar 'hum', only during play, very quiet, but once heard, annoying. It's an all-B&O setup (Beomaster 5000) and remains using either of 2 B&O 'double-shielded' 7-pin-DIN to 7-pin-DIN leads. And, just to make it more difficult to diagnose, it's only really noticable on the left channel...

Any thoughts?

Adam K, in warm(er) but rain-soaked London.

Re: Beogram 800 hum problem

Dillen — Thu, 25 Feb 2010 02:15:41 GMT

It's normal for a Beogram 6006/8000/8002 to groan a bit while accellerating and braking.
The eddy-current motor will unavoidably vibrate from the electromechanical forces and make a groan at startup,
when changing speeds 33/45 and when stopping the platter rotation.

Martin

Re: Beogram 800 hum problem

Piaf — Thu, 25 Feb 2010 00:45:02 GMT

I feel sure I posted this question before, so please forgive the redundant question, however my Beogram 8000 also groans a DEEP hum every time PLAY is selected. Once the platter comes up to speed the hum, groan, growl (whatever) goes away.

The sound is that of a strained electric motor, but the Beogram 8000 doesn’t have a motor, so what is this?

My 8000 is now performing nearly at the level of my 8002 thanks to Martin’s work, but this groan is annoying.

Jeff

Re: Beogram 800 hum problem

Medogsfat — Wed, 24 Feb 2010 16:24:37 GMT

The grounding for B&O turntables is done via the metal outer shield of the din plug. The original B&O cable will have been a Din to Din cable fully shielded to ground. I suspect the Din to RCA cable which you are calling the original is actually an after market item & isn't grounded this way. I would try as you suggest & run a direct ground wire from somewhere on the turntable chassis & see if this cures the hum.

EDIT - looks like Martin has already answered this while I was typing.....

Chris.

Re: Beogram 800 hum problem

Dillen — Wed, 24 Feb 2010 16:19:20 GMT

Yes, I suggest you try a direct grounding wire from chassis to chassis. Not all DIN/RCA
adapters pass both ground connections through.

Tonearm lowering faults like what you describe is very common and it takes a little explaining
of how the deck works to fully understand why it acts the way it does;

When you press play, the processor starts the whole deck up.
It orders the servo motor to drive the carriage towards the left.
When a certain amount of pulses from the shaft sensor has been counted, it
polls the tracking arm sensor to check for presence of a 12 inch record.

(If no 12 inch record is reported, the processor will allow the carriage
to continue to check for a 7 inch record, switch to 45 RPM etc.).

If a 12 inch record is sensed, it will slow down the carriage speed for the last
3-4 mm's until the tonearm is hovering over the lead-in groove.
All this is not timed but completely depending on pulses from the optical shaft sensor.
If the carriage is blocked or the belt is worn, the correct amount of pulses
may not be reached and the tonearm not allowed to be lowered automatically.
A slipping or too tight belt or a seized shaft/carriage/bushing will
not be able to transfer torque at the very low speed and/or the servo motor will not
have enough torque from the provided (low) voltage to move the carriage far enough
to reach the correct number of pulses.
Technically, your deck may be missing as little as a single pulse (less than 1/4 mm carriage movement,
not enough for most people to ever notice).
By activating the << button, you manually add the missing pulses by sending a higher voltage to the
servo motor and the deck will accept to lower the tonearm when you press play again.

Actually, after the correct amount of pulses has been counted, the system will
allow for the carriage to be backed out again enough to go just outside of a 12 inch
record and a manual lowering of the tonearm is possible.
This is useful when f.e. adjusting the tracking force dial.

Martin

Re: Beogram 800 hum problem

clio09 — Wed, 24 Feb 2010 12:13:35 GMT

Hi Martin,

Thanks for the response. First, the hum is constant not pulsating. Second, it is not coming from the deck itself, but the speakers. I have used the original DIN > RCA cable and the Soundsmith DIN > RCA cable, both with the ground wire connected to the phono stage (I'm using this in a non-BEO set up). Is there any other place to check for ground connections? Will adding a ground wire from a point on the table itself (one of the chassis screws) to the phono stage ground lug help?

The tonearm does reach the lead in groove, in fact it hovers over it. This one sounds like an adjustment is required. quite frankly I'm okay with the glitch since I can get the arm to drop and it only happens occasionally. Thanks again.

Tony

Re: Beogram 800 hum problem

Dillen — Wed, 24 Feb 2010 02:43:27 GMT

Welcome to Beoworld !

If the hum is pulsating, one pulse per platter revolution, it will be the tachodisc disintegrating (new available).
This type of hum will be audible from the deck itself (if you put your ear to it) and will transfer to the speakers where it will
also be audible to some degree.
If the hum is constant, it will be a missing ground connection somewhere. This type of hum will only be audible from the speakers.

The fault with the tonearm not quite reaching the lead-in groove will be due to dried lubricants on the threaded shaft
and/or the carriage bushing and/or a worn (too lose) or too tight servo motor belt.
Alternatively an adjustment issue.

Martin

Beogram 800 hum problem

clio09 — Tue, 23 Feb 2010 23:17:44 GMT

I own a Beogram 8000 which has a couple minor issues. The first being hum. This only occurs once the arm drops down on the record. You can hear the hum from the speakers at the listening position. If the arm is raised the hum is gone. It is not noticeable when music is playing, but definitely between tracks and very quiet passages. Any ideas what could be causing this?

Also, on occasion upon pushing play the arm will move to the proper position, but not drop. A simple pressing of the << or >> button, then play will enable the arm to drop. It will usually work fine for several LP sides, but will re-occur after the arm has set for a bit with no usage. Any ideas how this problem can be addressed?

Thanks in advance for the help.