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
Hello Beogram experts. Tried recently to use my vintage Beogram RX2 with original B&O MMC3R cartridge. No sound comes out of the left channel.
Performed the following tests:
1) Switched phono RCA jacks and the left side played eliminating the electronics...(initially only right channel plays)
2) Rotated cartridge 90 deg CCW and played record then rubbed needle from back to front. No output.
3) Cut RCA cord roughly in half and soldered a new set of RCA jacks on. Still no sound out the left channel.
4) Ohmed out the 4 pins (the cartridge) plugs into. One channel (left and right side) check out. I presume this is the right channel. The top pin checks out <2 ohms. However the bottom pin has a higher resistance sometimes showing open.
So I guess I am ready to take this unit apart for more diagnosis. Any thoughts or suggestions at this point?
Anyone take one of these apart before and have steps to dismantle?
Many thanks,
Marty
Hi - I would try and swap the cartridge before taking the beogram apart - I had the same problem in the past and something in the cartridge deterioates with age and can cause that. You can however have them rebuilt - Axel in Germany I think.
Andrew thank you for your advice. One quick question regarding the resistance readings from the 4 pins the stylus plugs into to the center pins of the RCA jacks. the left and right are less than 10 ohms and the top less than 10 ohms but the btm pin is much higher and sometimes reads open.
Knowing these resistance readings seems to eliminate the stylus. i could retest the stylus if there was a procedure? perhaps send out the stylus to be tested first in a known good RX2?
What are your thoughts?
Check the muting switch
Collecting Vintage B&O is not a hobby, its a lifestyle.
here the schematic
Hi Soren. Good call. except can u give guidance how to get to this switch? the assembly doesnt appear obvious how to dismantle is what i really mean...
Then if i find the muting switch can a replacement part be purchased?
Cant help you there, I only have the RX, and the RX muting switch is mechanical, not a relay, but get a manual, available for silver and gold members or follow the wires and PCB traces if the relay is PCB mounted.
Normally the bottom cover should come off easily, but take the cartridge off and secure the tonearm with a piece of tape, before before you turn the BG upside down, find some pieces of wood to rest it on so the tonearm dont get damaged, or leave the top cover on
Peter:A simple low tech check of the cartridge channels is to install the cart upside-down and hit play and tickle the stylus that is now facing up with a soft brush. If the original channel not making sound is still out the problem is in the turntable if the channel out changes then the problem is your cartridge.
Upside down would put the same coil at the same channel - just with a phaseshift.You need to rotate 90deg.
Martin
I have a moment where I often has to reboot it as all connection is lost except for Bluetooth
now b&o tells me to place my B&O equipment in a different network.
To me it doesn't make sense as I cannot use the app on my iPhone.
The connection is often lost if the moment has been turned off with the remote.
It has also happened during listening to TuneIn.
Problem got worse after the last update. Any suggestions?
Dillen:Upside down would put the same coil at the same channel - just with a phaseshift. You need to rotate 90deg. Martin
Ok, i was able 2 dismantle the unit enough to get to the muting switch. i also was able to do a resistance check from the tone-arm to the small pcb containing the muting switch which checks out. also on that same board the rca wires to the jacks also check out. but one channel is open when i go from the jacks to the tonearm. since that path includes the muting switch do u have a way (ohm meter) to tell if the muting switch is bad. if bad how can i get one?
The muting switch appears to be soldered 2 the brd with 6 pins.
It looks like a mechical relay of some kind...
I could remove it from the pcb using a solder sucker and copper braid to get rid of solder in pins 1, 4, 6, 11, 13, 16. then should i jumper wires to get rid of the switch for good?
Or worth replacing if part is available?
Without cartridge attached measure resistance from pin to outer skirt on the RCA plugs, should be open circuit on both right and left channel, with the cartridge attached you can measure the coil resistance in the cartridge, should be the same right and left, if this is OK, you can play again, without the relay, but you will not have the muting function
Can the muting switch be replaced or no longer available?
wigbuster: Can the muting switch be replaced or no longer available?
As I never had a BG RX2 in my hands, someone else must chime in. Or ask Martin (Dillen), he may have something in his dungeon
The muting switch cannot break the signal path. It can only short the signal paths to ground to mute them.Even if the muting switch is completely missing, the signal path will still be intact, but itcould help diagnosing if the switch is taken out because it will otherwise ground the signals whenthe Beogram is not playing and that will essentially shorten all four pins at the cartridge socket end while you measure around.Broken leads to the tonearm socket would not be at first, unfortunately.Martin
Martin, thanks for the advice. Sounds like its time to remove the switch and continue ohm meter testing. i have confirmed the wiring in the tone arm is intact.
You wouldnt happen to know where i could get another muting switch?
A bad muting switch can NOT mute. It lets one or both channels through at all times.Not the other way around.
Unless your muting switch has failed in an "always shorted" way - which is very unusual and highly unlikely - the muting switch isnot the problem in your deck.
Hi Soren, I checked the resistance without the cartrrdge attached. the resistance between center pin and skirt of the rca. they both measure less than 1 ohm. my understanding from Martin is that this is the job of the muting switch?
So if i remove the muting switch then both resistance vlaues should be open.
My plan is to remove the muting switch so i can measure the coil resistance of each channel in the cartridge and going from there to each respective channel.
wigbuster: Hi Soren, I checked the resistance without the cartrrdge attached. the resistance between center pin and skirt of the rca. they both measure less than 1 ohm. my understanding from Martin is that this is the job of the muting switch? So if i remove the muting switch then both resistance vlaues should be open. My plan is to remove the muting switch so i can measure the coil resistance of each channel in the cartridge and going from there to each respective channel.
You can measure the coils in the cartridge on the pins on the cartridge, see the schematic I posted earlier.
And yes without the muting switch the values should be open circuit.
If the relay is a type with a plastic cover you should be able to take that off and place a piece of paper or plastic acetate between the contacts, this way no need for desoldering.
Just a shout out for all the professional help on this site. outstanding.
Current status:
Muting switch removed, measured and confirmed tonearm wiring is intact. measured resistance between center pin and ground skirt on both rca jacks, both are open.
Plugged in cartridge, measured resistance for each coil.
One is say 740 ohms and the other is open. this should clearly indicate the stylus is out.
So where should i get a replacement?
Also since they have mmc1 thru mmc5 which one is the best?
Here repairment of MMCs I have the MMC4 with elliptical diamond (repair Euros 119.00) and an MMC2 with Shibata diamond (Euros 245.00)
Depending on what you are going to play, and which amps and speakers using, you will have to decide whats best for you, to comply with MMC 3 I would go for the Euro 245.00 one. I use my MMC 2 only for very good or new records
Speakers: Klipsch Lascalas
Amp: Adcom GFA 555 II
Preamp: yamaha cx-830
With the horn tweeter and midrange drivers perhaps a higher end stylus is worth it?