Help with Beogram 4002

[Richard Davis]

I’ve owned this 4002 since new.  It was always been a little noisy on the audio output.  There is a notable 60hz hum on the output which has gotten worse with age.  The hum is present when the relay kicks in to enable the output from the cartridge after the arm makes contact with the record.  I’m wondering if it could be a bad capacitor but I only know basic electronics so I’m not sure how to troubleshoot.  Has anyone had this problem.  Any help would be welcome.  I  do have a service manual.  Thanks.

[Mark-sf]

That type of hum is likely a grounding issue. You did not say what the turntable is connected to. If you are using the DIN->RCA adpater then it must be the phono one which has a separate ground wire or you will get hum. If you are going DIN->DIN it may be a bad chassis ground connection in the TT or amp.

[Peter]

Agree with Mark – are you in the US – wondering about the 60Hz! If using as described as above, a simple wire touching the metal DIN plug casing run to earth should alleviate the hum. Had to do this many years ago when someone borrowed my Beogram for a party! (Danceproof!)

[Richard Davis]

Hi.  Thanks.  I am in the US.  The unit is a type 5523 and came supplied with RCA connectors.  I’ve had the problem for decades and is independent of what it is connected to.  I recently replaced the ground wire with a thicker one but I still have the problem.  If I disconnect the ground wire completely the hum gets really loud (louder than the audio).  As it is, when I listen through headphones everything is quiet until the TT unmutes when the arm drops.  That is when I hear the hum.  Music on the record will mask the hum until it gets between tracks on the record.

[Mark-sf]

Can you take the back right square cover off by sliding the trim forward and snap a picture of that entire area? It’s possible the chassis ground is not properly connected. Also if you remove the cartridge, you should see a small flexible copper tang coming out of the bottom of the black connector. This connection is designed to ground the body of the cartridge since moving iron cartridges with their relatively low outputs are susceptible to hum. If that was damaged or missing that could also be your problem. Here is a link to a picture of the cartridge holder. If you have an ohm meter with the stylus cover on but the arm lowered, you should have continuity {<1 Ohm) between you ground wire and the cartridge shell.

• This reply was modified 1 day, 21 hours ago by Mark-sf.
• This reply was modified 1 day, 21 hours ago by Mark-sf.

[Richard Davis]

Thanks.  Because of your direction I think I have found the problem.  It will be a while before I can test.  I watched the video about the RCA and DIN connections to the relay (mute) board.  It included a wiring diagram and picture of how everything should be wired.  My unit has the chassis ground wire, shield, and signal return all tied together.  The proper way shows the signal return and the chassis isolated by a capacitor.  I will rewire and test once I get my turntable put back together.  I am amazed by the quality of the resources on this site.  Thanks to everyone involved.

[Mark-sf]

Yes, that capacitor is important as chassis ground and signal ground must not be tied together in the turntable.

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