Login to view imageHello Gents

I am still troubleshooting the arm dragging problem and have been delving deeper into the heart of the 4002. I have removed this lamp? and found it and the surrounding area drenched in sewing machine oil. My fault as I am unused to lubricating turntables with Elna oil which is almost as thin as water (the dispenser belongs to my wife and she cut the nozzle far too much)! and the stuff ran everywhere it shouldn't have🙁

I have just cleaned-up the mess and vacuumed and used compressed air to get the stuff out of the black box in the pic.

Is there any way I can test the lamp to see if it still works?

Regards

andre/dauphine

Put an ohmmeter across its leads and check for continuity.

Martin

Hi Martin

Thanks🙂

I've just checked. No continuity🙁 I will have to check the two scrap decks for a replacement.

Regards

andre/dauphine

Lamps can blow and break for any reason, even from mere vibrations but with another lamp fitted
I suggest you check the voltage across the lamp, just to make sure it didn't blow
from overvoltage.

Martin

Hi Martin,

Thank you. I found these from the scrap decks. The lefthand lamps in each are still OK so I will use one of these. There could have been a bit of vibration or shocks over the months I worked on the 4002 as I used a very small plastic mallet on occasion to tap some of the top plates into position. I will avoid this from now. 

I will also check the voltage which I think should be between 21.5 and 24Vdc.

Regards

andre/dauphine Login to view image

Your pictures show the light sensors not a lamp! The two above belong to a gram4000.

Also a blown bulb should not result in a the sled responding as you suggest, and oil should not conduct BUT if there was enough it could have acted as a light gathering lens in front of the sensor or something equally strange!

Put everything carefully and meticulously back and test again then if problems still persist start some proper troubleshooting or you will cause far more serious problems in my opinion!

What I would do in your position - remove platter, disconnect shutter lamp (the glass bit above the sensors), press start let arm go to play then see if the problem persists if not reconnect bulb and go from there, if it does disconnect sensor etc...

Correct.
Those are the sensors. (The ones with four leads will track both ways!).
The lamp is a wedge socket type and should be very easy to replace.
It sits right above the interrupter (where the sensors sit below).

I often find a little oil around the screws holding the assembly and also between the
two plastic halfes. Nothing to worry about, unless it's really soaked.

Martin

Hi,

A couple of innocent questions:👍

1) are both arms parallel and at right angles to the deck?

2) how long does the pickup arm take to lower?

It seems to me that a bad sensor lamp would just bring the pickup arm close to the sensor arm and skip the same groove over and over again...

I am sure that this problem is a badly adjusted paddle and or detector at the base of the carriage tube.

It does not need to be far out for the arm to travel continuosly inward once the stylus hits the record.

Login to view imageHello Gents

I'm sorry I missed all your valuable posts (it seems my auto notification got switched-off).

Yes, I'm still busy troubleshooting and must admit I'm getting a bit depressed about the situation as more symptoms are manifesting - the arm no longer returns, let alone drag the needle across the record etc. The keypad has all new switches and tests perfectly on all 7 controls out of the turntable etc and so on.

Anyway, I'm now looking at the possibility of non-functioning sensors. Menahem's LED + 1KOhm resistor mod works as the turntable operated perfectly with it. Although I don't suspect any of the sensor devices to be faulty, I must find ways to test to see if they work. The paddle (is that the slotted plate?) and the sensor device below - how would one test this?

I have already removed this device from the turntable and tested for continuity but this must have been an incorrect test. Instead, if my multimeter is set to Ohms and one touches the two leads, there is a resistance reading. If one shields the lamp? from light, the resistance reading changes.

The 3 other similar devices I retrieved from the scrap 4000's behave exactly the same. Can I therefore assume this sensor can be eliminated from troubleshooting?

Next, earlier this evening, I switched off all lighting in my workshop and photographed a LED-like device which appears to be a UV lamp.

The attached pic shows the lamp lights up if start is pressed. Do you think this checks out OK, looking at the attached pic?

The paddle/slotted plate and its mountings have not been disturbed and is tightly clamped to the arm base. However, it is possible that the plate may have been disturbed slighly upwards when I removed the sensor below. I will re-check this now and check its position according to the manual.

The oil there has been cleaned up completely. No longer an issue.

Thankyou once more for your valuable tips and input. I will follow them all until the problem is solved.

Regards

andre/dauphine