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
Hi everyone, I have been working on getting a BG6000 back to life over the last few weeks. So far its had some new caps, belts, a good clean, some new pots for speed adjustment, some new globes in the speed dials, a good de-oxit of the relays and other pots, some new resistors, a clean of the solenoid mechanism and associated linkages, the arm ruler has been cleaned and aligned and a full alignment of the arm as it would not lift in the run off position and an alignment of the diaphragm as the arm wasn't tracking correctly. I also levelled the platter to be the same height as the turntable surround The machine looks great and is sounding good and tracking nice and straight.
I have always noticed this but not paid a huge amount of attention to it until last night when I began to finish the small adjustments on the tonearm. The tone arm and the detector (sensor) arm sit at a downwards angle towards the front of the deck. The clearance between the platter and the top of the detector arm reduces as you move towards the front of the deck by about 5mm along the length of the arm taking the clearance from the platter from 23mm (as per specs) to 18mm at the end where the B&O logo and lamp sit., because I have the two arms vertically aligned, the tone arm also sits at this height and provides only 3mm or so clearance above a record which gets a bit scarey. I can manually raise the tone arm a bit higher but then the two arms wont look right. I have dropped the platter as much as I am comfortable by adjusting the bearing height without scraping the solenoid leads but I suspect this isn't the best long term solution.
The detector arm and tone arm dont appear bent or to have suffered any direct impact, its almost as though the entire carriage mechanism isn't sitting level in the deck. The platter is level (as checked with a spirit level) but the detector arm is not. I am unable to find any adjustment in the service manual for the horizontal angle of the tone arm and detector arm as a whole or the detector arm individually. I did look at the two metal bars on which the carriage assembly slides and verified they are seated correctly, I suspect lifting the front metal bar a little would right this issue however I am not sure that 'fudging it' is worthwhile as it could put the carriage leadscrew out of alignment.
Has anyone experienced this? any ideas?
Any help much appreciated.
Drew
Hi everyone, a bit of an update - hopefully this can help a few people out.
My Beogram 6000 appears to have had a hard life, I was having issues with the arm intermittantly raising and the unit returning to standby whilst playing records (run off stop), and at this point I decided to take a "ill fix it until I break it' principle. So i removed the entire arm carriage as well as the metal rods on which it slides, the servo motor and the carriage shaft.
As it turns out, the 6000 has suffered some kind of impact in its earlier life, the place where the front metal rod runs through the carriage assembly hsa been bent upwards causing the entire front of the carriage assembly to sag down, there was some other small impact damage at other points.. After inspecting I decided this couldn't easily be bent back into place so the solution was a second hand arm carriage (which I do not have) or to compensate for this somehow.
Once the front metal rod was removed, I could see two small grub screws mounted into the suspended chasis - one in each holder where the rod rests, I undid these to raise the sitting position of the rod which levelled out the carriage and the arms. The next thing I had to do when replacing the threaded shaft was to put two small washers under the shaft so that it was at the correct height for the now raised carriage assembly. Once I verified the front and rear arms were now in a position whereby the carriage assembly was level along the length of the arm travel, it was time to reassemble.
The next thing I did was remove the ruler and ruler optical sensor, for some reason the plastic housing had been stuck to the PCB with a piece of double sided foam tape in addition to the standard clips, this tape had lost its adhension and was forcing the top of the face of the sensor housing away from the ruler, so the two surfaces werent parallel, I removed the entire housing and sensor, refitted the sensor to the housing and replaced it on the pcb with a small amount of adhesive glue, now the two surfaces (ruler and sensor housing) are about 1mm appart along the travel of the ruler and the early run-off error hasn't shown itself once the deck was re-assembled. The next step if I do experience early run-off will be to replace the bulb and also do the modification to add an extra resistor to the PCB to remove noise from the sensor circuit - has anyone done this mod? I think its 1R91 where you add an extra resistor..
The mechanics of the 6000 AC version are mind boggling, I hope some of this info would be useful to someone.
Andrew
Very interesting Andrew!
However, a few pictures would have been a welcome bonus!
Jacques
In this picture you can 'kind of' see the slope of the arm.
This the left hand red circle shows the area where the mounts for the carriage assembly were bent upwards, the second red circle shows the mis-aligned sensor housing (and hence sensor). You can also see both arms were bent to the left, god knows what impacted this unit, but interesting to note that nothing on the boards below seemed damaged... neither is the underneath of the casing...
Hi everyone, my last question about this 6000.
The arm motor is too responsive - this sounds stupid I know. I have set the diaphragm and the shutter up correctly so that when the table rotates by 2-3 turns the arm makes its first movement (testing without a belt) and when playing the arms stay parallel and rotates every turn. I have adjusted the bottom plate (eccentric screw) which moves the entire photosensor box so that its aligned squarely and all seems fine in that area.
My issue is this, the smallest amount of light entering the photosensor seems to create a disproportionate reaction in the arm motor. This is okay when playing a record with grooves which are cut correctly but is a problem for lead in and lead out grooves and records where the grooves are not aligned all around the record (where the arm has some sideways movement usually).
When the arm lands on the lead in groove it runs very quickly to the first groove which sometimes gives the cantilever a hard time. When the arm hits the run out groove, it pulses/jerks its way along the run out groove, ie it moves slightly out of parallel, then the motor drives it back to straight and the motor cuts out, then it goes off parallel again and once again the motor goes off again... rather than going smoothly as it does on my 4002 where the motor and sensor maintain a constant slow operation across the run out groove..
I have tried all extremities with adjustment of the shutter diaphragm and the eccentric srews underneath and ended up aigning the eccentric screw section with the same alignment as my 4002 and then adjusting the shutter as per the manual.
Is there some way of adjusting the responsiveness of the motor to the light received by the photosensor. I dont know the history of this unit, there is a tranditional incandescent bulb in the sensor housing - I have not removed the photosensor to inspect. I know we can adjust the << and >> speeds by using the pots on the main board however when looking at the circuit these appear further up the circuit from the signal from the photosensor to move the arm whilst playing.
Any help, ideas or suggestions or encouragement would be greatly appreciated to help me in this final step with the old 6000.
Just an update for everyone, after checking the voltage at the globe in the sensor housing, checking the wiring for the photosensor and checking the resistor 3R1 as well as slow speed transport adjustments we were out of ideas. As a temporary investigation we added a 5k pot (what I had laying around) on the sensor housing lamp and then set resistance to about 680ohm. This dimmed the lamp in the sensor housing by about a third and finally the tonearm is now behaving correctly, moving slowly along the lead in and lead out grooves and also allowing a bit of lateral movement when playing records with grooves which aren't perfectly cut.
The bulb in the sensor housing sure looks original however it seems to be very much overpowered for the application. I got the idea of the pot from other posts about the Beogram 4000 which had a pot fitted to the sensor lamp to make up for differences in production of bulbs I believe? Anyhow now I have the decision (as the pot isn't the ideal solution) to either add a 680k resistor and leave it, or look to replace the bulb with the correct bulb which might be a little harder to source.
Has anyone else encountered this before?
Replace all the bulbs with LED's
Click Here for a full BeoGram 6000 Restoration Guide
Menahem