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 4002-5503 (ac motor heavy platter). Everything works , carriage transport photo cell on tracking arm everything, arm goes to beginning of record and drops but only tracks till the play in the tone arm is used up then begins skipping. In observing with the deck plates removed when the record is playing the motor is not making those small turns that track the tone arm as it plays. I emailed Menahem Yachad (Condor Audio) and he said the main circuit board would have to be rebuilt? Does that sound correct? Is there anything else I could look for. Oh and yes the photo lamp behind the "ruler" seems to be illuminated? what else is there to look for? Thanks in advance guys.
Have you checked the actual tracking force of the tonearm with the cartridge? Don't just go by what it is set at. Actually measure the weight with a stylus gauge.
Sounds more like a burned lamp in the tracking opto.This opto sits inside a black plastic housing at the foot of the carriage.An interrupter (metal arm) goes through a slot in the top part of the housing, swinging together withthe tonearm to interrupt light from the lamp shining onto the sensor, both inside the plastic housing.
Under normal circumstances, with the metal covers off the Beogram, you should be able to seethe light from the lamp shine out fmo the plastic housing.
Martin
Martin, thanks for the reply, yes the lamp is illuminated. And the tracking force was checked with the B&O gauge. When the arm
begins its movement to the left does it not activate a contact that starts pulsing the carriage motor to track?
Just to make sure that we are talking about the same lamp;It's a common mistake that the light that shines down onto the record surface has anything to do with the tracking of the recird grooves.It's only function is to determine if a record is present - and its size.
The tracking takes place at the foot of the carriage.The "contact" you mention is in fact an optical "contact";Inside a plastic housing (we are now below decks - at the foot of the carriage), shielded from ambient light, a lampshines onto a sensor.Between the lamp and the sensor a metal arm (still below decks) can interrupt the light according to the arms angle.The arms angle is determined by the angle of the tonearm (above decks).
When correctly adjusted, as the tonearm tracks the record grooves it moves away from being tangential to therecord grooves (away from parallel to the deck).This causes the sensor light to be interrupted which in turn causes the servo motor to start rotating to allowthe carriage to "catch up" and make the tonearm tangential to the record grooves again.
I am talking about the lamp inside this plastic housing. Not the lamp inside the arm next to the tonearm.
Martin many thanks, I will check the one indicated. I was initially referring to the one that shines through the plastic ruler( seen in the pic parallel to your arrow. Did not even realize that there was another lamp and sensor under the tone arm I thought the lever operated contacts down there. Other than the disassembly of the tone arm is this difficult to replace.
You don't have to disassemble the tonearm. Just the top of the black housing itselfand pull out the lamp.But look for the light first, when the deck is playing you can see the light shining out throughthe slot where the interrupter arm enters the plastic housing (if the lamp is working that is).No light - replace the lamp.
Martin, Bingo! The lamp does not illuminate. Shinning a small pen light through the slot causes the arm to begin movement. So that checks out. The lamp seems to be soldered in or IS that a socket in the lid (cover) of the lamp assembly. The circuit board is showing that is a 24V lead going to the lamp. Next and last question what is a good source for this lamp? My hats off to you sir you do know these machines. I watched a demo of a 4002 TT in 1975 and was in awe at the time however could not afford it (along with the power amp preamp and tape deck) that I purchased at the time wanted one ever since. Many thanks for your help.
It can be a socket or it can be soldered, depending on the version.If you can provide a photo, maybe we can see what type you have.
Here is the picture of the underside of the cover with the bulb. Is it possible to test the bulb say with a small
battery to verify its function and rule out another circuit issue? On the circuit board the lead going to the bulb indicates
24v.
With a DC voltmeter, you can measure the voltage across the lamp when it is supposed to light up.If you have voltage but no light the lamp is defect.If you have no voltage, the fault lies elsewhere.
Martin, Thanks for your patience, I am new to Electronics repair. With the belt off and the stylus on a record, checked the voltage across the terminals it was showing 22.7v , so back to one of my earlier questions. Where do I source this bulb? Did it look soldered or socketed I have not seen both so I am unable to tell?
Confirmed then.And it looks soldered.
I don't have that lamp in the drawer but I would try something like this, in the 24V 40mA type:http://www.ebay.co.uk/itm/Sub-miniature-wire-ended-bulbs-range-14v-18v-24v-28v-5-5mm-x-12-5m-2pcs-SMW-/390808042128?pt=UK_Light_Bulbs&var=&hash=item5afdf97a90
Martin, got the bulb from the UK (thank for the tip) installing it was really something. The bulb is made into the black plastic lid of the housing, it
was epoxied in with the two wires coming out the back. I was able to chisel the old bulb out clean out the hole with a Dremel tool. After inserting
the leads of the new bulb through I used clear silicon RTV to secure the new bulb in the hole where the factory orig. was. Of course the leads had to
be soldered to the circuit board as well. Now it cues up and tracks just fine. Since I have never had it play all the way across a record I never came
across another problem. Once the arm tracks all the way across the record it does not want to lift. Now you can gently touch the shutter mechanism
under the arm and it will lift and return and shut down. Does the new lamp need to be aimed or what any ideas? Seems to be mechanical adjustment.
There is an adjustment for the interrupter.See the service manual (which I don't have at hand right now).