[Mark-sf]

TK wrote:

Platters also come up for sale quite frequently in various marketplaces, ranging from USD $50 to $100.  In the mean time, you might consider milling two solid discs with a diameter of 10cm each.  Place a layer of rubber on the bottom one for a bit of grip.  Place the bottom disc on the spindle with the rubber facing up, next the record, last the top disc as a weight to hold the record in place and level to the bottom disc surface.  You might need to make the top disc a bit heavier to provide additional stability.  I haven’t tried this myself, but I feel like it would work fine, provided it is balanced properly, and can compensate for the 1.5g of downward pressure provided by the tone arm.

This is really not a good idea. First, the record need full support underneath which is 300mm. Secondly, for this motor design the correct weight is very important as there is a tight servo loop and additional weight can cause undesirable rotational inertia. Finally, the MMC1-4 cartridges tracked at 1.0 to 1.2 grams.

 

[Mark-sf]

The platter diameter is 300mm and the height is 24 mm; however, it was not a solid piece of aluminum as it was cast with the underside hollowed out. I believe the weight was around 1.5kg but was never published. A solid piece would be too heavy at about 4.6kg. This would require you to remove about 16.mm of material except for a 1-2mm outside edge. For this motor design it’s essential for the platter to be light weight as the servo system with its ~200mm rotor would be impaired by the higher inertia of a typical direct drive platter. You would also need to stencil the black ribs. The black rotor that supported the turntable platter was part of the motor. Do you have that?

• This reply was modified 2 days, 20 hours ago by Mark-sf.
• This reply was modified 2 days, 20 hours ago by Mark-sf.

[Mark-sf]

There is no possibility to pick a single song.

[Mark-sf]

I have not seen this type of malfunction and I would suspect it may be related to how you reassembled the motor. This is because it generates the frequency that ultimately governs the speed. Unfortunately that can’t be confirmed without an oscilloscope or a frequency meter. You can get a multimeter that measures frequency for under $50 (as well as capacitance), so I suggest its a good investment if your current one is inadequate.

[Mark-sf]

First, I would check all of the voltages around the 1IC3 and the 8.5V at P1 Pin 3. While you’ve replaced the electrolytics, sometimes the tantalums can also fail. If you have a scope or frequency meter you can check the feedback frequency of P1-1 which should be 125Hz for 33 and 167 for 45. Now all of this pertains to the DC gold motor.

If you have the older AC silver motor then the frequencies are 42.3 and 57.3 respectively at 5V AC. You should have also changed the 4000mf motor cap. You should also get 11.4VDC on its transistor side.

[Mark-sf]

Yes there is though not inexpensive at https://www.designedav.com/connect-bo-turntable-to-modern-systems. You can make one yourself with 7-Pin DIN male and female connectors where the L/R signal uses male RCA connectors to connect to an external phono preamp and pins 6 & 7 are directly connected with a wire between bypassing the preamp.

[Mark-sf]

B&O does not produce an external phono preamp for its turntables, but there are many out there depending on your country. Here in the US but available internationally, a particular fine one is the Schiit Mani.  As to repair ability between the 7000, 6500, and 5500, they are equivalent as they share many of the same parts. It was the 5000, I would not bother with.

[Mark-sf]

The Beogram 6500 or 7000 would be your best choice since it came with the phono preamp built in. Otherwise, it is the same as the 5500, which would require an outboard preamp. I would avoid the 5000 which is older.

[Mark-sf]

The answer is unchanged. Follow the procedure in the linked manual or video.

[Mark-sf]

You should realize with a cartridge likely over 30yrs old and and obvious suspension issue and unknown diamond wear, that you are likely doing damage to your records which may in total be more valuable.

[Mark-sf]

I’m afraid it does. You are not likely to be able to get it rebuilt, but Soundsmith sells an SMMC4 for $230 as a replacement. They are reputable.

[Mark-sf]

I would first check to make sure that at rest, cued up, the stylus is centered. If it is, then the shutter is misadjusted. You may see evidence of that when the arm is cued down, in that the tonearm moves a bit laterally instead of dropping straight down.  When the belt is off, and the arm is cued down on a record, it should drop straight and then not move for 2-3 revolutions of the record.

[Mark-sf]

You mention shorting transistor 6. The one directly controlling the solenoid is IC4. What you need to check is whether TR9 gets .7V when you press the down arrow. Most 400x turntables at this point need the electrolytic caps replaced at this point and their are kits available to do that online such as beoparts.com.

 

 

[Mark-sf]

You’re welcome. Enjoy!

[Mark-sf]

These cartridges are 50 years old and there is little doubt that the suspensions are shot even if the diamonds are fine. These diamonds, especially the 6000 are so small that unless you have a stereo microscope, you would not get an accurate picture on wear. You can confirm that the channel(s) is out due to they coils in the cartridge my measuring the hot and gnd of each channel at the cable with the arm cued down. If it measures significantly higher than 1000 ohms the cartridge is not salvageable.

[Mark-sf]

If the base of 8IC1 is getting .7V when the arm is set down, then then it should be effectively “grounding” the end of the relay which is what you did manually. If that is not happening it is bad.

[Mark-sf]

Since it works fine on 33, I would check a few things about the 45 speed.

1. Do you have the problem with a 45 LP as well as a 7”?

2. There is a speed adjustment dial at the on the upper edge of the control square as well as a trimmer on the circuit board that you should try cleaning or at least moving back and forth several times.

3. I would check that the platter is not touching anywhere and moves freely up and down/l-r when a record is on.

4. The single likely culprit is the speed selector relay. Since 45 is rarely used, the contacts have been known to oxidize and the best approach is to replace the relay.

[Mark-sf]

It’s actually Pin 1 that is biasing 8IC1 to turn on and close the relay. You are getting the correct input voltage so I would look at the trimmer 8R2, 100mf cap, 8C1 and diode 8D2.

• This reply was modified 2 months, 4 weeks ago by Mark-sf.

[Mark-sf]

I would check the voltages on the muting relay board. You should have 21V DC on P1 of the P8 Connector and .7V when the tonearm drops to open the muting relay. You also might try cleaning and adjusting the muting relay delay trimmer, 8R2.

• This reply was modified 2 months, 4 weeks ago by Mark-sf.

[Mark-sf]

Do you hear the click of the muting relay after the arm sets down? Have you tried using the cartridge from your 2402?

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