BeoGram 3300 L/R Channel problem...

Hi People,  I'm new to this forum/site and also new to vintage B&O.  I've got myself a BeoGram 3000 fairly cheaply and am having an issue with the sound and just thought I'd ask some people who maybe know common problems or the best things to check.

 Right, first off I'm missing the left channel completely with audio only coming out from the right. I've sourced it to be a problem with the turntable for sure.

 I've done a continuity test on the leads but I seem to get a the same readings (closed circuit) no matter where I put the leads.  The MMC4 cartridge is second hand and bought from a different place to the deck but is ment to be in working condition, would the cartridge fail on just one channel or is it more likely to be something else?

Any help/ideas would be very helpful as I'm at a lose........Thanks 

Sorry,  correction on that......Its a BeoGram 3300 with the MMC4 Cartridge

Welcome.

I think there is a way to check the MMC4. You can search to make sure of the procedure but you can mount it upside down on the tonarm and gently brush the stylus and see which channel now works. This can give you a diagnosis of where the problem lies. These old cartridges can fail but can also be rebuilt. You could also try the cart on another TT and if it works OK, then the problem is elsewhere.

Dave.

Thanks Dave,  Very helpful.

 I've tried the flip test on the MMC4 cartridge ans all seems well with that as the dead channel didn't move so now I'm assuming a problem with the wiring somewhere....

I've done a multi-meter test and it looks as if there's a short somewhere if my testing results are right, I get a closed circuit across all wires, when tested from RED+ on the turntable I get a reading across both rca pins and outers which seem incorrect to me???

Should I only get a closed circuit across just the red rca pin with the rest open?

 

Almost all Beograms have a muting switch (to prevent arm liftup / dropdown pops) that actually short circuits the audio lines to ground when the arm is up, so that measurement result is expected.

To pinpoint the problem you will probably need to open the Beogram. As you measured a short at the output, the problem is likely located at the muting switch or somewhere before it.

Thanks, from what I've found out it could well be the muting switch to blame for the issue as all wires seem fine. Is there a way to bypass the muting switch or a tried and test way to clean/refurb? 

Ross.

Thanks, from what I've found out it could well be the muting switch to blame for the issue as all wires seem fine. Is there a way to bypass the muting switch or a tried and test way to clean/refurb? 

Ross.

Right,  now I'm starting to think its the cartridge again!!!!!

 When I do a continunity test without the cartridge in all is good!!  but when I do it with the cartridge in I get a short across the red+ & both - cables (earths) but the white+ cable is all good......does this sound odd to anyone???

 

Really pulling my hair out now....

Rosco:

Right,  now I'm starting to think its the cartridge again!!!!!

 When I do a continunity test without the cartridge in all is good!!  but when I do it with the cartridge in I get a short across the red+ & both - cables (earths) but the white+ cable is all good......does this sound odd to anyone???

 

Really pulling my hair out now....

Actually, I think the red one is good and the white is at fault.
Remember you are measuring through coils inside the cartridge.
No continuity is bad for a coil.

Martin

Right, so now I'm really lost........I'm thinking the carftridge is ok, I've removed the mute switch and still the same problem, replaced the cable from the mute switch to the din plug/rca........so now what?  anybody have any ideas?

Ross.

Measuring directly on the cartridge pins, you should find two coils.
That is two pairs of pins with continuity.

Martin