Beogram 2400 – muting switch

[Wojciech Herchel]

Hello – does anyone know where is the muting switch located in Beogram 2400? I have an issue that I have very weak sound in the right channel (and it moves when I swap RCA jacks around). I’ve tested the cartridge etc, now am thinking there is something wrong with the muting switch, as when I press stop the sound momentarily returns to the right channel, before the arm is lifted.

 

Just wanted to see how it looks / clean it etc. any ideas? had a look at the manual, but couldn’t figure it out from it…

[Mark-sf]

There is a sliding shorting switch near the base of the tonearm that is activated when the arm rotates to unshort the + and – leads of each channel.

[Wojciech Herchel]

Thanks – I suspect I need to lift up and take out the whole top plate, not just the platter to access this switch?

[Mark-sf]

No you access it by removing the bottom cover.

[Gabe]

Ref: Shunt (mute) Switch. Yes, your description; cartridge ok, but moves with changing RCA plugs, indicates the moving shunt.

You have to close the cover and turn your player upside down, and remove the 3 base clips & screws (NOT the 3 hinge spring screws!). And then about 2 inches in from the front on the bottom there are two deep hole hidden “captive” Phillips screws (you may hear plastic clicks as you loosen them). Then remove the black plastic bottom, called a plinth.

Hi, I recently took my B&O 2400 out of 35 year storage, and discovered issues with the tone arm lift, and then the control panel fell into the body. OMG! While searching for clues on various forums, I found this forum too. I was able to fix all my problems, and also fixed an eBay junker I bought for parts to new-like as well. Both required basically the same work.

I fixed the Tone Arm lifts by using fancy fine synthetic oil on the Brass Plunger Brass Housing interface. Soak a drop – gently work it – add a drop work it some more, etc.

Both Control Housing Assemblies were a complicated clean up and re-build, with added custom structure to support broken parts. They now work excellent.

While researching and fixing, I  encountered two B&O 2400 Shunt Switch designs. Both are activated by the long arm that activates the tone arm lift and decent. My two B&Os have the same design, I believe the more recent of the two. The other I saw in photos of a guy who was having lift issues. Both designs have a fixed fiberboard with terminals for tone arm SUPER fine wiring and RCA phono cable end soldering.  A vertical fiberboard anchored to the sliding arm has shorting-knives in it that enter tabs on the fixed board. If you have problems, I suspect debris in the tab slots and shorting-knives (easily cleaned), or far worse, damage to the SUPER fine wires coming from the tone arm, or their delicate solder connections. You have to have the skill to count angels on a pin head to be able to fix those SUPER fine wires. Be VERY cautious moving around those fine wires.

So, hopefully, all you need to do is clean the shunt tabs and knives. AND not touch those fine wires. If that fails, perhaps it’s faulty tone arm wiring. While you have the unit open, DEFINITELY lube the brass lift plunger, and remove the four screws holding the Control Panel Housing, One By One, and add a washer under the heads of the screws. You will certainly see some cracking in the clear plastic cover  around the screws. Some lube inside would be great too.

Good luck, let us know how it works out – the cause of the missing channel… how were those other parts I mentioned?

Gabe

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