ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
My Beocenter 7007 has been fine for years. But now there is a very weak output from the left speaker (CX100) when using the turntable. The output is fine for about half a second when the stylus first lands on the record then changes to very weak. Output from the tuner is perfect. The cassette has no belts so I can't check that (If I can fix the turntable fault, I'll replace the belts next).
I have a wrecked 7007 that I bought for parts and have swapped over all the circuit boards in the turntable side but this has made no difference (I am a profficient mechanic but have little experience of electronics!)
Does anyone have any ideas that may help? preferably by robbing the right part from my spares unit. Or can you recommend a good repairer in the Cardiff area?
Do you have a spare MMC 5 or similar stylus to check, they can go faulty too, though it's rare. Only other area to think about is the switch board PCB that controls the path of signals from each source to the pre and then power amps. If you have had parts changed and the fault is the same then it shouldn't be those. The 7000s series are nice and simple to work on but there's very little spare space in them and when opened up and closed again, make sure all the wires go back in the right places especially if you've had to disconnect any of the little black earth wires that connect to the chassis. The switch board PCB is in the base RH corner, can't remember the PCB number but this is where all the connections (from everywhere) join up. Just make sure non of the 10 way plugs are loose or the PCB has not bowed and there is a solder joint touching the metal chassis under the PCB. I had a 7000 that used to cut out (power recycle) sometimes when not placed on a level surface or when lifted in one corner due to low voltage parts being shorted to earth. Sometimes a bit of cardboard tucked under PCBs can stop this. So, best you can, while it's playing a record, gentely lift the right corner and see if this changes the sound. A lot of electronic faults actually end up being caused by some physical thing or other, especially with B&O due to the compact design and tight spaces around the electronics.
I had a similar issue on my Beogram 3000 years ago, it was a defective MMC5 cartridge. One channel was very weak, I think it was the left but can't recall for sure, so it can be the cartridge.
Jeff
I'm afraid I'm recovering from the BeoVirus.
Thanks. I have tried lifting the corners with a record playing but that made no difference. I'll open it up again this evening and reseat all the connections on the switch board (unfortunately, that's one of the parts that is broken on my spares machine!). If that doesn't work, I'll try to get hold of another stylus.
I'll let you know how I get on
Thanks both. It is a faulty MMC4 cartridge. I found out you can test it like this:
turn the sound low, make a note of which speaker is OK, take off the cartridge and put it back sideways so the stylus is pointing to the side, gently hold up the tone arm and press play.. you may need a record on the turntable. when the machine thinks it is playing, gently stroke the stylus and if you now get sound from the other speaker, your cartrige is toast.
a new one is lots of money so I'm on the look out for a good second hand one!