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…Here’s what B&O did to ameliorate the resonance of the air chamber created under the hard dust cap of their midrange, which is just the same woofer, just modified pole-piece.
The driver with the ventilated magnet is not a midrange!
Both drivers were custom produced to each their specific jobs here.
Personally, I don’t believe much of it before I see some form of documentation.
No, you cannot just listen. – You can measure much more than you can hear.
If you sat down and took some readings, you will see that
the midrange and woofer drivers have quite unique T/S parameters, and you would also see that those parameters go out the door, when you fit rubber surrounds.
It’s a fact. It can be measured and calculated – but most people will actually be able to hear that something is out of normal.
Look at a scope, enlarge waveforms, analyze distortion and its source.
And that comes based on decades of experience with all matters B&O audio
and lots of speaker experiments, measurements and whatnots.
All facts.And – as a moderator – I have also been weeding out posts that went into audiophoolery.
Beoworld forum is not for buying or selling snake-oil.Why don’t you give us the readings, so we can see, that what you are doing are in fact improvements?
Martin
There should be no pairing.
If you are sure, that the Beo4 is working, it’s most likely, that the remote receiver is not
longer working in the BeoSound 2000.
If the latter is the case, I made this kit:https://www.beoparts-shop.com/product/beosound-century-ir-remote-control-pcb-service-kit/
Martin
Beomaster 6000 4-channel?
Martin
Martin
They are not 1970s – but then again, there weren’t that many LEDs in 1970s B&O.
Martin
Good job, and thanks for the feedback!
Martin
Question is not why something works.
Question is why something doesn’t work.
In your case, – where things basically works when commanded from outside but not
from its own operation panel, there must be a problem getting the commands from the panel to the processor.Most problems of this sort are caused by cables, connectors, solder joints and
stuck switches. However, the keyboard reading circuit could also be at fault.
If the display on the front panel is also garbled, perhaps some circuit shared by those
two functions should be looked at.Martin
When you fit the black subplatter to the hub, make sure to match the
three “protrusions” on it with the three small indentations on the hub.
If you don’t the subplatter will ride too high.And you have the platter upside up – right? Your photo shows its downside.
Martin
Front panel cable/plug correctly seated?
One or more buttons stuck down?Martin
You should be able to find out the other leads as well using an ohmmeter / continuity.
Martin
A handrule is that the “warmest” color is always right.
If your cable has red and white, red is right and white is left.Martin
If the relay is chattering, it could be the diode inside the housing has shorted.
I have seen this happen a couple of times.All fine inside the relay housing? – Check the adjustment and position of arms and levers
and that the small wire spring on one of the relay box arms is still present.Martin
Great progress! I would measure the woofers as the doped cones will likely change the parameters causing a crossover modification.
I agree. Even a few grams usually make quite a difference.
– And even more so will the change to rubber surrounds.
I tried it a few times, but when I measured and compared T/S I found them
to be far out compared to the original specs, so I ripped the rubber off
again and changed it back to foam. After a few hours playing time, allowing
the new foam to losen up a bit, everything was spot on, back where it belongs.
I never used rubber again, where foam was used originally.But of course it can be done if you really MUST have rubber.
A compensation for the lack of cabinet volume
needed to satisfy the T/S with rubber (I seem to remember them requiring
8-10 liters) could perhaps be made by introducing a filler driver of some sort, though
driving it right phase-wise could be quite a task and would almost
definitely require a bit of signal processing – not least because it would
almost definitely need to be rear-facing due to lack of front area.
A passive radiator would require a too large area to have any effect, – far
more than what is available – as would surely a bass reflex system,
– and we must not forget that if both the midrange and woofer drivers
are changed to rubber surrounds, both will need compensating, and
not necessarily in the same way.
But why? – When you can just fit foam.I am looking forward to seeing the frequency response and new filter calculations.
Martin
If some lights come on, but nothing more happens, it could point to the
CPU not running or not being reset correctly.
Most like a capacitor problem.Check power supply voltages and look for excess ripple from dying filter capacitors.
Martin
Wrong wattage lamp for the FM1 indicator?
Yes, they are critical.Martin
The lifter arm with the small pad should work in the groove, so it can lift and lower the wheel.
Martin
Read my post in this thread:
https://forum.beoworld.org/forums/topic/beogram-1902-dust-cover/
Martin
I like to use a teflon-based oil called “Liquid bearing”, but any good long-term oil or light grease would be fine.
Parts here.
Martin
Note the note about cable and socket matching here:
Martin
You don’t replace it – it must be taken apart, cleaned and lubricated. It can all seize up
in dry lubricants.
New idler wheel, new lifting arm friction pad and a new belt.
The motor will almost surely also need new bearings in order to run correctly.
All of these parts are available.Martin
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