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
I have a 4002 that a year and a half ago after replacing the capacitors and getting it to work I inadvertently touched the leads of a voltmeter together that were on the transport motor when I was trying to adjust the speed of the tonearm travel. Stupid me did not think to use alligator clips, everything went dead. I set it aside for over a year but now I have replaced some transistors I suspected might have been faulty TR20,22,23, and 25. I have got it back to life except for this problem:
Pushing the start button with or without a record on the deck the arm travels to the spindle switching from 33 to the 45 position as it should and then returns to the rest position.Does not see the record.
It will travel in or out after pushing start with the < or > buttons.
It will not lower when the v button is depressed.The arm is lubricated and moves freely.
The lamp in the sensor arm is lit and the tracking lamp at the base of the tone and sensor arms is lit. I have also tried to adjust the lamp in the sensor arm over the magnifying lens as well. No luck.
The led or lamp behind the plexi ruler I have tried to tell if it is working but cannot. I thought before I was able to use a digital camera and tell but that does not seem to be the case now. I have a working 4002 that I tried the same trick with but no luck with that one either.
Capacitors have all been replaced and the board checked for cracked solders or traces, but may try doing that again. This is a problem that is similar to one that I found in the archives that was "Beogram 4004 won't stop or lower arm" in 05-17-2009 by zorro349. It was suggest by Dillen to check C19 in that post but I know the capacitor is good I went ahead and replaced it after reading the post.
The OP did not indicate if he fixed the problem but the implication was that it was a lamp.
Any suggestions will be welcome, I just don"t have an oscilloscope or much technical expertise so please be patient with me if I come back with questions or ask for clarifications.
John
After my recent success with restoring a Beomaster 1900 I thought I would try my luck again with my Beogram 4002 which is not functioning. I checked a suspect solder connection and gave it another try but same result as before. The arm as before would not recognize a record on the platter and would go to the end of the record and then return to parked position. if I tried manually to use the down button no solenoid click or armm lowering. For no logical reason I removed the platter and sub platter with the circuit board visible, and tried to see if the arm would lower manually. Sure enough the solenoid clicks and the arm lowers. Hit up and it raises. Put the sub platter and platter back on and try to manually lower it on a record and no solenoid click and no lowering.
This makes no sense to me but it seems like someone might have a clue other than me.
Hi John,
My understanding is the 4002 has to meet 2 conditions in order to attempt to activate the solenoid and drop the arm. 1. it must not see the rotating platter ribs (ie they are covered by a record or the platter is removed or stationary, and 2. the ruler under the deck must be in place to tell the arm when its in the 12" or 7" zone.
If there is a fault with either circuit then you wont get an arm lower. For the ruler. some units are IR and some are a lamp. I know my 4002 series 5523 is an IR lamp but I suspect there is a slight chance your unit might be a lamp being an earlier revision. It would be worth checking that there is voltage getting to the place where the lamp or IR emitter would sit, then try again with the digital camera/camera phone in a dark room to see if you can see the IR (as you have previously attempted).
Without a platter on, if the lamp on the ruler is not giving out a signal then I still expect the unit wouldn't lower the arm as it doesn't know where the edge of the record is, however without the ruler fitted I have still been able to manually lower the arm on my unit.
The fact your unit lowers the arm without the platter leads me to believe that you are getting a signal from the ruler circuit which makes me think (as you have done) that it something in the detector arm circuit. Have you tried with the platter fitted but without the turntable belt fitted so the platter doesn't rotate? the arm should still drop.
The only other thing which stops the units lowering the arm besides lubrication (mehcanically at least) is that the diaphragm/paddle attached to the tonearm is not aligned correcty which means that light is reaching the photosensor when the arm attempts to go down, usually the symptom of this is the arm will get to the point it where it would lower, the solenoid will fire to put the arm down and then fire again almost immediately to raise the arm, or it would lower and skate across the LP, however in circumstances when the paddle is too far out of alignment (towards the spindle of the platter rather than towards the right-hand edge of the unit) the unit wont even attempt to lower the arm in my experience... It might be worth checking the diapgragm alignment just to be sure.
Andrew
I have measured the IR emitter diode behind the ruler when the arm is traveling across the board and it is 1.13 volts which I suspect is not enough voltage for the detection of a record in place but I am not sure.
Any thoughts?
Andrew:The fact your unit lowers the arm without the platter leads me to believe that you are getting a signal from the ruler circuit which makes me think (as you have done) that it something in the detector arm circuit. Have you tried with the platter fitted but without the turntable belt fitted so the platter doesn't rotate? the arm should still drop.
It's a good idea to test that. The ruler system is part of the equation only when the arm is travelling at full speed in automatic mode, and while playing the lead-out grooves (it depends on the waveforms created by the stripes passing through the light port - it doesn't do anything when stationary).
You should always be able to drop the arm manually - unless the detector circuit thinks there's a bare platter underneath. So I also think the problem is somewhere in the detector arm circuitry, which apparently is now falsely preventing the arm drop. I think I'd start looking around 1TR4 and 1TR6 (not sure if these numbers match the particular type you have, but the circuitry drawn around the detector arm lamp in the schematic).
--mika
Hello Mika,
The arm will only drop when manually I stop the auto travel with the down burecord s without either a record, platter or sub platter in place, just the circuit board below. The solenoid will click and the arm drops. Even as suggested in an earlier post I tried it with the platter in place but without a belt on it and it would not drop, and no solenoid click. I will look at TR4 and TR6 as you suggest.
john
Still doing some trouble shooting. Question, I said the position sensor lamp behind the "ruler"was measuring 1.13 volts. I tried a continuity test on the lamp leads and got no audible sound so am guessing maybe the bulb is bad. I have a spare part board but it does not look like a bulb like the one on the machine in question but an IR type. Are replacement bulbs available or can I use the IR from the spare part and do I have to ad another components like additional resistors to make that work?
I am attaching the images of the lamp that I took off the table which shows no continuity with a voltmeter and has 1.13 volts going to it when on the table. The second image is the IR lamp on the part board which I have a question as to whether or not I can switch the two lamps.
None of these are lamps.You should be able to see the light they emit using a digital camera (cell phone camera).
Martin
I put the IR back in place and tried using a cell phone camera to see if I was able to detect a light being emitted, but could not. Does the fact that the turntable control pad shows it switches from 33 1/3 rpm to 45 rpm indicate the IR is functioning or not? Also is the 1.13 volts measured at the IR correct?