Woohoo! I just got my new Beogram 6000 (the older 4002-like model), all in one piece - after I assembled it, anyway. And it sounds great with the MMC20S which was delivered with it!

Everything seems to be fine mechanically. However, someway through the record it will spontaneously lift the arm, return to rest and stop. Is this another "get the cap kit" -case?

It's still cold from travelling in the delivery van, but I suppose just warming up won't fix it, as the seller warned about this problem.

Special thanks to auric for the packing advice earlier (regarding 4002, but I ended up buying another unit) - the seller apparently took it all, multiplied by two. I must have spent half an hour just getting all the parts out... 

-mika 

Hi Mika,

congratulations to Your new beogram 6000; I´ve the beogram 6500 and I like the sound with the MMC 2.

In the past I´ve had a similiar problem with my beogram; here the tone arm lifted up always in the last third of the record.

It was an problem in the sliding mechanism of the tone arm; the b&o technicans have cleaned this mechanism and they did an relubrication of the sliding mechansim.

This was about two years ago and since then my beogram works very well.

I hope this can solve also Your problem.

beorebels

beorebels:

It was an problem in the sliding mechanism of the tone arm; the b&o technicans have cleaned this mechanism and they did an relubrication of the sliding mechansim.

Thanks, lubrication will be one of the first things I'll check (I've learned this with about every single one of old B&O gear I've looked into...).

Nevertheless, the arm seems to move rather effortlessly, I think the real cause is somewhere in the disk detection logic. If I leave the arm raised, the machine won't stop by itself, and I don't think it actually detects anything; good thing I watched over closely while trying to play a single for the first time, the arm was going to lower on the platter...

The light in the detection arm seems rather dim. Is this a symptom/cause for something? The hard part is that I' ve never seen one of these machines in action before, so I have no idea how they should look and sound while operating...

 -mika 

OK, now I've been inside the deck, and cleaned and lubricated the two fixed tracks of the transport, as well as the worm track. This actually helped a lot, now I've been able to play two consecutive record sides without the machine cutting out, but the problem still remains.

I noticed that the tone arm "leads" a bit while playing, it's closer to the detector arm at the moving (cartridge) end. Is there an electronic tracking adjustment somewhere, or am I really supposed to loosen the clamp in the base of the tonearm pivot and turn the reflector block around? This might be the only problem, since the deck most often cuts out right after lowering the arm, when it is supposed to run fast on the leader of the record...

-mika
 

Gee. Now I've replaced the two large power supply caps, as well as every single electrolytic (including tantalums) on the main board and the one on the sled. The machine still makes spontaneous automatic stops at seemingly random positions, though perhaps not so often. Anyone care to comment on what to check next?
 

After some experimenting, I noticed that the problematic positions aren't random at all any more. They are invariably

• right after start, even so that the arm doesn't have time to lower
• at the 45 rpm landing zone

...i.e exactly where the wide black stripes are located on the position encoder bar, or whatever it's called. I removed it temporarily, and now the deck doesn't know where to lower the arm nor where to really stop, but doesn't stop by itself either. Apparently the logic is confused of when it's running and when it's seeking.

I guess I'll continue by spending some quality time studying the schematic. Must be a shorted/open diode, or something...

Clean the ruler and gently bend the IR sensor and emitter as close to the ruler as possible without touching.

Martin

Thanks, tried that. Didn't help :-/ (actually didn't bend them as they're on plastic holders, I just adjusted the ruler as close to the sensor as possible)

Ummh... IR? We are talking about the same 6000 (a.k.a 4002), right? This has an incandescent light and I guess an LDR...

The analogue control logic is diabolical and defies human mind. I think I'll replace it with a microprocessor At least I've found out why the platter detection doesn't work, the signal coming from the arm is very weak, only about one volt after TR9 (should be six). I guess the sensor is out...

-mika
 

Usually, the sensor either works or don't. The lamp is what becomes weak in most cases, it could also just be out of focus with the lens system. The lamp should be in a position very near the lens, in some cases actually touching, and with the filament centered with respect to the lens.

When I said IR related to the ruler, it's because an IR system is used in some versions and that just came to mind. There seems to be a lot of different versions, easily 25 or more and I'm getting older. 

Martin

Progress, I think - the machine isn't imagining the OFF command, it really accumulates the "run-off" signal voltage at the test point over C33 from pulses coming from nowhere, while the ruler sensor is in the dark. But not always :-/ (Wish the nice folks at B&O had designed the machine so that I could probe with the oscilloscope while the platter is on...). Other than that, the pulse decays seem right all around.

At this point, I think I'll crack a beer and listen to CDs for the rest of the evening

-mika
 

I never found out where the spurious pulses come from while the ruler is at a black stripe. Possibly induced by the servo firing. The first transistor stage still amplified them to full level anyhow.

I added a couple of power supply decoupling caps (the mainboard doesn't have any from the factory!), reduced the sensor-amplifier coupling cap to half of its original size and made the pull-up on the amplifier base heavier so it would need more pulse energy to turn off. Now the deck gets past the 45 rpm landing zone maybe two times out of three.

I'll put the covers on (how stylish!), clean up this mess, and return to the project some sunny day...

-mika

Strange fault, it's not because ambient light can fall on the sensor ?

Martin

I don't think so - at least not completely. I tried it a few times in a completely dark room with no noticeable difference. I'm starting to suspect the sensor itself might misbehave when it's in the dark. I was thinking about the moving wirings from the carriage too at first, but since the problems are strictly on the black bars now, I think I can rule them out.

Now that I have all the covers on the deck it has played a few sides without problems... maybe it likes the warmth  

(BTW, I'll need a new belt sometime soon and my local supplier doesn't carry belts this long anymore. Please drop me a PM with instructions, if you have them... )

-mika
 

Mika,

You have a PM !

Martin

Just an update, in case someone is still interested - I've been playing through a good part of my LP collection today, without a single hickup. Dunno what happened, but I'm not complaining I'll carry the oscilloscope back to work on Monday (and list the Dual CS5000 for sale)...

-mika 

Final update, I hope - I fiddled with the position of the detector arm light bulb to get the maximum platter signal amplitude and tweaked R35. Now even the disc detection and speed selection work The signal is quite marginal, though; I guess the bulb is pretty worn. It does get the correct voltage.

-mika 

Thank you, thank you. Tomorrow I'll need to raid the flea markets in search of something new to play

A final observation, which I'll post in case it might help someone searching the forums for troubleshooting information later: at first I was scratching my head over why the selection of record size & speed for 45 rpm singles only worked every other time, i.e on the first time the arm always tried to lower at the LP landing zone. Then it occured to me that the worn out belt was slipping, and the platter didn't reach correct speed in time for the detector circuit to "see" it! On the second try, it was already turning... there's a filter in the detection circuit, and it needs the correct frequency of moving bars under the sensor. Wicked people, those Danish engineers!

-mika