I took apart one my of parts 8002s.   Never opened one up before.   I thought someone said the mute relay was in the top left corner but the only switch I see is under the tone arm on the right side.

I've labeled a few things that I am not sure what they do.   If someone could help fill in the blanks would be appreciated.  

I could not find the sensors that are somewhere behind the tonearm.   I took a picture of the backside of the tonearm, where would they be?

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Item "A" is OTR2 and 3 in the schematic. You can see more details link.

Item "B" is OIC1 in the schematic. You can see my recap of the two electrolytic caps .

Thanks Sonavor,

Is the mute relay/switch even visible in my photos?   Just wondering were it is.

Sonavor, I noticed I have a missing part of two of my 8002s.  That little spring you have in the picture.  I need to fasten the top plate better.  I just temp used a little duct tape folded in 1/2 but its a little too thick.   How did that 3M work out?   Where did you get it?

I'm thinking just get a spring from a hardware or maybe a pen to substitute for that spring of unknown function.

" Under the aluminum deck panel however, there is a small spring on the left side. I guess it was for grounding. Maybe for anti-static?  In any case, don't forget to put it back in place before resealing the deck with new double-sided tape."

Yes-any small spring like a shortened pen-spring will work to act as a ground for the trim-plate.

The muting relay is in the DIN socket assy in the upper left corner, above your red A. You need to dismount it and turn it over to see the relay inside. It has a clear plastic cover. Be careful of the 2 lightweight coaxial leads soldered to the little circuit board. They can only tolerate a few bendings before breaking off and are challenging to repair!

Aside: is there any way to edit your own posts on the forum?............YES!!

What I'd edit is to get clarification about the spring you saw on a picture i don't find in this string.

Yes. There is supposed to be a captured grounding spring under the platter trim-plate.

Also, the screw in the shadowy tonearm picture which isn't very distinct is (if it is brass, ~7mm head, has a "V" groove in it's waist, with the visible rod engaging that waist) is the adjustment for centering the parked-up tonearm position when the arm is not released and under servo-tracking control, as has been previously mentioned.

pfcs49 wrote:

Aside: is there any way to edit your own posts on the forum?

Yes, on your own posts...the "More" drop-down menu should have an "Edit" menu item like this -

Thanks, right now I am getting oriented with the inside of the unit.  Before I go looking at the circuit diagrams I like to know what purpose of the parts are.  I don't totally understand how it works. .  Before I attempt any fixes on my own I have a ways to go education wise.    Thanks for the help.   The parts 8002 is sort of a learning TT for me.  Can't ruin it as its already broken.   

The DIN socket on one of my working ones must have a loose hold down screw.  If I grab the cord plugged into it I can jiggle it easily.   On the parts 8002 that same DIN socket is very solid.   Wonder if that could be part of the issue with the channel that drops in volume after hours.   Maybe one of those thin coax leads you mentioned are weakened from it being a little loose.    Just a guess.   

Also do you know where the sensors for the worm drive are?   I guess they detect if the tone arm angle changes then sends a signal to the worm drive to turn.

BTW what is the purpose of that spring ground?  Seems to work without it.

The spring is to allow the metal surface discharge static - see

The DIN socket/muting relay assy (8005044 on wiring diag) is secured by a single screw and two curved tabs that hinge up/out of the base after releasing the screw. If the looseness is from the screw, the entire assy will be loose. If not, then something about the socket inside is wrong. This should be checked, especially given your complaint.

Looking at the the long brass worm-screw from the normal/front perspective, the sensor is at the right end; there is a shutter-wheel on the end of the screw. The sensor is U shaped, with a light source and a photo-sensor. The adjacent motor and belt turns the shaft and the sensor sees each slot in the wheel; the signal goes to the processor which is the brain; it counts and keeps track of velocity and position of tonearm.

The sensor, light source, and light slot for the tonearm angle is in the under/front area of the tonearm assy or tonearm carriage as I call it. As the arm moves out of tangency, the shutter diminishes the light to the sensor and the processor responds by (slowly) turning the arm motor. AFAIK, the 8000/2 B&O only move forward in the groove; I think my Yamaha PX-2 is bi-directional.

A good thing for you to do would be to take your "parts" unit down to the point where the entire upper case and covers are gone. You can now lay a piece of corrugated cardboard over the area where the main circuit-board will naturally want to return to; this will insulate it from the electronics and steel base below it. Remove the control pad and the transformer from the case. Reconnect the ribbon wire for the keypad (pay attention to how it should be and don't get the ribbon-wire 180*/backwards!). Plug the transformer to the main board being careful that it plugs into the terminals correctly (the terminals are equip-distant so you can plug it together incorrectly when the case isn't there to only allow the right orientation. In this configuration, you can put a disc on the platter and play it-even through the stereo. You can swap things around to see if they work or not. Everything is pretty accessible for doing electrical tests. The voyages are low enough ton not be a safety worry. You are better off working on this unit and bringing it to life and heath. Once done, you will have a much clearer sense of the bigger picture and be ready to move on to the others, otherwise, I'm afraid they will all become parts units!

The spring's purpose is proper electrical engineering-to bring the major metal parts of the unit to a common ground plane, which includes dissipating static among other things.