BeoWorld North America

Re: beogram 4002 tonearm issues

marfinhead — Tue, 20 Dec 2011 11:58:00 GMT

I haven't had time to work on it lately but will keep you up to date. The holidays are keeping me busy

Re: beogram 4002 tonearm issues

Step1 — Mon, 19 Dec 2011 09:59:26 GMT

How you doing with this? Did you get a bulb off Martin?

Re: beogram 4002 tonearm issues

tournedos — Fri, 16 Dec 2011 08:41:19 GMT

Yes, the sensor actually needs to see the bars to not drop the arm, which can be confusing (was to me, anyway - everybody just talks about how the deck senses the record!).

The sensor in the arm is rather critical to the correct positioning of the lamp. There are simple optics in between, and the lamp needs to be at the right spot in relation to the lens so that the sensor sees the image from the weak light. I guess it could refuse to function even if the filament is in a different position inside the bulb when you are not using the correct type of bulb.

In any case, try fiddling with the position. The bulb usually needs to be very close to the lens on the underside the arm, so that it projects a nice round spot of light on the platter. This can be a lot of trial and error, unless you have an oscilloscope so you can look at the signal after the amplifier circuit.

Re: beogram 4002 tonearm issues

marfinhead — Fri, 16 Dec 2011 08:26:05 GMT

one more issue... in my excitement that the tonearm was dropping at cue I missed the fact that it was dropping with or without an LP on the platter. Do I need to adjust the sensitivity? or is it possibly that the 6volt grain of wheat lamp I used is just off specs and not pulling the right current?

and or will it function if the photocell is fried?

I looked at the service manual to find the right pot for adjustment but I can't seem to find the same label that they list in the manual and I don't have the vertical layout like in the manual.

Re: beogram 4002 tonearm issues

marfinhead — Thu, 15 Dec 2011 20:50:34 GMT

I got the damper adjusted it's working pretty darn well now, the cartridge seems pretty decent too.

Thanks so much for the help Olly I would have banged my head against the wall for a lot longer with out your help.

Bob

No just to put it all back together and I'm done

Re: beogram 4002 tonearm issues

marfinhead — Thu, 15 Dec 2011 20:36:18 GMT

and I should kick myself the shutter was being limited by the limiting plate on the tracking arm. duh.

I do need to correct the rate of the arm drop it is extremely slow. 2-3seconds

but other than that I think we're in business

Re: beogram 4002 tonearm issues

Step1 — Thu, 15 Dec 2011 20:02:55 GMT

Take things one step at a time. This issue will probably not have anything to do with the trim pots just follow the steps above with the aid of the service manual and see how things go from there... Then when all is good you can replace the trim pots!

Re: beogram 4002 tonearm issues

Step1 — Thu, 15 Dec 2011 20:00:26 GMT

Hi ok so it sounds like the arm paddle is the next thing to check. You need to check it is dead straight with the tone arm and the required gap so it does not snag the top or bottom of the sensor housing. Center the sensor cam (after loosening the lock screw a little) and then try again.

Re: beogram 4002 tonearm issues

marfinhead — Thu, 15 Dec 2011 19:57:20 GMT

As i looked through the forum and service manual I'm thinking it is probably the tracking circuit as 1 or 2 of the trim pots seem a bit corroded looks like I might be doing some replacement there too.

Re: beogram 4002 tonearm issues

marfinhead — Thu, 15 Dec 2011 19:01:01 GMT

I removed and soaked the parts and relubed them, That was the problem with the the arm dropping (still must have been a tad gooey). the lamp is working the solenoid fires at lead in and the arm drops.

Now I have the arm racing across the record. I'll look at the service manual to try and diagnose but If you have had this issue I would appreciate your input.

Thanks again we are getting closer.

YOU WILL NOT DEFEAT ME BEOGRAM 4002!!!

Re: beogram 4002 tonearm issues

Step1 — Wed, 14 Dec 2011 17:33:44 GMT

Good luck and please let us know how you get on :)

Re: beogram 4002 tonearm issues

marfinhead — Wed, 14 Dec 2011 14:56:46 GMT

Ok Thanks for all the advice Olly,

I will strip it down fully and soak the old lube off the relube and reassemble and yes I have replaced the belts. I think it might be what you think; A: the drop mechanism is still gummy and B: the lamp is the wrong specs so drawing wrong on the circuit and effecting the reading. Hopefully we can get this table going again.

Thanks again for your help.

I will keep you up to date as I proceed on the repairs.

Bob

Re: beogram 4002 tonearm issues

Step1 — Wed, 14 Dec 2011 08:16:17 GMT

Hi ok so the position detector is more likely fine then. Regarding the solenoid arms yes you need to pull them all off including the damper clean out with isopropyl and re-lube (singer oil or light machine oil is great NOT 3in1) and install. You might have to adjust the damper after relubing - please don't screw the screw down much below the top I have recently seen a few examples and it basically wrecks them! Anyway, there is a small angled arm, attached to the inside of the sesnor arm base that links the tone arm to the damper which possibly might need freeing up and lubing, but I do not recomend you remove the sensor arm unless you are happy you can get it back DEAD straight and in EXACTLY the right spot!

Regarding the tonearm sled no there should be no speed change throughout its journey. Not sure if you said you had replaced the belts (again contact Martin) but I should imagine the worm gear (screw thread) needs cleaning of old gunk and relubing with a mineral oil. Also, it is absolutely important that the worm is parrallel to the motion of the sled motion and at right angles to the bearing that holds it near the motor. Again I remove this part but you could clean and relube without removal.

Make sure it is parallel (both vertically and horizontally) with the metal guides along their length (move sled to extremes, but bear in mind the worm might have a slight bend which complicates things!) and if anything is out there are two screws to adjust horizontal parallelism and two for vertical on the bracket. It is important the bracket remains at right angles to the thread as this will bind if not.

You may find a simple clean and relube plus new belt (don't forget to degrease and clean pulley's!) is enough (also don't forget the nylon bearing holding the screw thread near the motor!) but I just pull everything out when I service anyway so all the above has to be bourn in mind!

It is very revealing to use a current meter in series with the motor and run the arm back and forth a few times if anything is wrong here you will see it in the reading!

Anyway, please take your time with this deck and make sure you double check everything, it is too easy to forget something and then things can go very wrong very quickly!

Re: beogram 4002 tonearm issues

marfinhead — Wed, 14 Dec 2011 07:15:29 GMT

I didn't fully strip and dip the components I will do that and I will try to get a proper bulb you're probably right that it is the rating on the bulb messing with things and my idea of smooth and what it really should be is probably different .

It does changes speed at the 45 zone on the ruler so I think the position sensor is working.

Does the tonearm group slow when it reaches the LP lead in then lower? I guess what I am asking is what are the "normal" characteristics of operation. Thanks again for your help I will try to contact Martin to acquire the proper bulb then we will diagnose from there.

Re: beogram 4002 tonearm issues

Step1 — Mon, 12 Dec 2011 21:35:57 GMT

First thing I would do, is get a properly rated bulb from member Martin (Dillen) as the one you have fitted might not be pulling quite enough juice for the circuit compromising zener / transistor etc. to see it - this circuit I describe does not relate directly to the light detector on the same arm...

If after that the arm still shoots past the lead in (BTW remove the platter you obviously don't need this atm!) then you can start to look at the position detector etc.

It concerns me that you can't drop the arm at all though. When relubing the solenoid etc. did you check that it could move freely and quite easily afterward? You should really strip this part (levers and damper) and thoroughly de-gunk then apply fresh mineral oil..