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Hello,
I got a Beogram 4000, and yesterday when I was listening he stop to move the tonearm to the beginning (right side) and doesn't turn off ( does not collect to starting place) when I press the button.
I've disassembled the motor belt and the motor never stop moving to "left" direction, if I press to "right" he just lower the rotation.
I will put on someone with knowledge and tech ability to solv the problem, but till then I would like to understand what's really happening.
thanks in advance!
regards
https://youtu.be/RIoCkbOiMlc
Format: ???Duration: 01:33
Hi,
There are quite a few Beogram 4000 repair threads here on the forum. It is a great turntable. However, it is almost 50 years old! That being the case it really needs a complete going over. That early Bang & Olufsen linear tracking turntable was their first of that kind and has an early analog control system. It also, surprisingly, has some early logic (AND, NAND) gates to go along with several physical sensor switches that the control system depends on to know what the motors are supposed to be doing. A failure in one or more of those sensors is most likely the cause of your problem. The problem could be as simple as a mechanical switch being out of position. The bad thing about buying a used Beogram 4000 that you know nothing about its ownership history is you don't know what other people may have done to it. That is why a complete going over of the unit by someone experienced in these is a must if you intend on having a perfectly working Beogram 4000.
-sonavor
Thank´s,
it seem´s that´s some command that tell to the motor to rotate in fast speed to left direction, maybe some leaky transistor?!
The most common problems are old deteriorated electrolytic capacitors (and tantalum capacitors), connections, solder joints, power supply problems and mechanical mis-adjustments.
A restoration process usually begins with changing out the old capacitors and rechecking the Beogram. The first thing to check is that the power supply is providing the expected voltages to everything it supports. Once that it is working the restoration moves on to basic functional tests which can involve more electrical work. But always suspect a bad connection first before looking at components like transistors, diodes or integrated circuits. On the Beogram 4000 there are also a couple of optical sensors. One in the fixed arm and one in the tangential arm base (for the record tracking). The signal from those sensors should be checked at some point. If all of the electrical components (and their voltages) test out okay then you can work on the mechanical position of sensor (switches). When the control function of the Beogram is working again you will need to go through the service manual mechanical adjustments for the platter and tonearm. -sonavor
Problem solved after 3 hard weeks.
The problem was it was on 1TR28 and 1TR29, for further users with same problem, I've changed 1TR30 and 1TR31 either.
Meanwhile I bought another B4000 completely off for parts, but I've changed my mind and I'm working on him, is working at 85%, just need to solve one problem with the detection sensor, the arm always stop at the edge of a 12" l.p. and play from there, if I put a single l.p. (45rpm) the arm lows as I got a 12", but I'll solve that with patients.
Many thanks to Sonavor for the helping comments here and by email (beolover)
Regards to all.
Hugo
Does the tone arm continue to drive into the centre of the platter when there is no L.P present, or does it still attempt to lower as if a L.P was present?
Craig
Hi Craig,
it attempt always to lower as it was there a LP.I will change this night probably the OTR4, that seems that could be at short circuit, i have not measure him without connection, i prefer to do that with another Transistor to change if it´s the case.I took apart the sensor arm and the photo-sensor is working.Se, i´m not from electronic, because of that i take more time to understand all the schematic of each process.RegardsHugo
How did you test the photo-sensor? do you have an oscilloscope you can use to test the signals....
No, for the moment i just measure the answer with different light intensity, and i notice that e give an resistance answer. Probably doesn´t not completely mislead.
You need a pulse output from the photo-cell, Martins advice below is a good place to start....adjusting the lamps position in the lamp holder may work for you....
Also - check the lamps position in relation to the lens system.It needs to sit right in the sweet spot.
Martin
0tr4 unsolded and measured... is fine! Got to look again to the electric scheme.
Another day, another problem.
Now the solenoide doesnt work and bulb on sensor arm is off (I measure 8v going to bulb lamp) ..
Hi to all.For other user´s i wright here the solutions that i found to each problem´s.Beogram #1
Solution - Substituted 1TR28; 1TR29; (Forward) 1TR30; 1TR31 (Reward)
Solution - Substituted 1TR10; 1TR11, Still not working, but after my Beogram#2 acuse same problem, days later, i found the final solution... Just change 5V 50ma lamp that blew solve the problem on both Beogram´s, Solenoid circuit begin´s to work again
Beogram #2 (that i start restoration)
Photosensor just cracked, i substitute with one Osram Photodiode SFH206K TO92
Now i will get my Beogram #2 to a specialized store to final adjust´s, because as i said i´m not for electronic and don´t have the necessary measure tools. Thank´s to all that try to help and that post during the years is problem´s and solution´s in this Forum.Regards