[Mark-sf]

Unless you are connecting the table to a unit with a DIN input you do not need to put back the DIN cable. While that is a cheap RCA cable it is one that B&O used on later 4004s and many others. If the hum does not change when using the ground wire to your phono inputs it’s likely that it’s not properly grounded internally. I have replaced many of these and it needs to be done correctly since the DIN cable has a double shield system. Are you comfortable with soldering? If not a competent tech can do this but I would simply use a higher quality RCA cable.

 

[Mark-sf]

Sorry, there was a typo in my response. I meant 88cm.

 

[Mark-sf]

This is not recommended due to the risk of condensation shorting out or corroding the electronics. I would recommend you bring them out only when you are enjoying the good weather and views.

[Mark-sf]

TimeBandit wrote:

Martin: Do you know what that preset time would be?

This time is not adjustable and is only a few seconds sufficient to close/open the drawer. The issue is that the motor should not be continuing to run. Since it is seeing 13v when closed, the OpAmps are active. Since the drawer does open and close, the signals from the two pins of 1C8 are working, but may not be resetting.

[Mark-sf]

Thanks Martin. This then means you need to check how long those pins are active in each direction. If the go back low once the drawer closes then I would look at the OpAmp driver circuit to see if there is a bad cap for example that is keeping the output latched.

[Mark-sf]

Those relays are not likely your problem as they only govern pre-emphasis and end up simply bypassing a resister. Your best bet is to try and trace a test tone from a CD. If you don’t have a scope an AC multimeter can work if your tone is a bass one.

[Mark-sf]

It is not recommended that you switch topology types as many of those changes are in notch filters and B&O likely had different drivers or a different batch that needed compensation. As far as parts quality, since all bands are in parallel and there are a lot of parts, I would focus on replacing any electrolytics in the mid and tweeter circuits with poly caps as it does not appear there are any iron-core inductors in there. Check out either the Dayton or Fast PA Series from Solen. I have had excellent results with these.

[Mark-sf]

My recommendation would be to add an RIAA board inside such as https://www.ebay.com/itm/185373986428?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=i_P7_Iv4Tsu&sssrc=2349624&ssuid=WrB3U2kWQBO&var=&widget_ver=artemis&media=COPY. This is just an example of one that can run off of the +12v single supply. I’m sure there are higher quality ones if you scout around. You can find the user and service manuals on Beocentral.com.

[Mark-sf]

I know the muting board had the additional pattern so it could be the same for the main board. It is easy enough for you to check. In any case the newer sealed ones are your long term solution.

[Mark-sf]

There is no switch involved. The direction and action is controlled by two pins, 21 and 22 on IC8 that provide a differential voltage to dual op-amp IC9. I do not have access to the service manual that may explain how end of travel is sensed.

[Mark-sf]

There are two springs that govern the damped closing of the cover. This is discussed at the end of the service manual at https://beomanuals.com/manuals/Beocord/Beocord%205000/Beocord_5000-Service_Manual-version4.pdf.

[Mark-sf]

I am afraid you need to open the top to get to the adjustment for the photo sensor. It’s described in the service manual available at https://beomanuals.com/manuals/Beogram/Beogram%206002/Beogram_6002-Service_Manual.pdf. You can also view a video on how to open it on Rudy’s site at https://beolover.blogspot.com/2017/07/beogram-8000-opening-beogram-to-service.html.

[Mark-sf]

I’m afraid you are going to need to open it up to access the adjustment. This is explained in the service manual at https://beomanuals.com/manuals/Beogram/Beogram%206002/Beogram_6002-Service_Manual.pdf. You can also check out Rudy’s video on opening it up at  https://beolover.blogspot.com/2017/07/beogram-8000-opening-beogram-to-service.html.

[Mark-sf]

My approach would be to first check out the power supply as there are multiple ones in this unit along with 4 fuses. You can get the service manual at https://beomanuals.com/manuals/Beocenter/Beocenter%209000/Bang-Olufsen-Beocenter_9000-Service-Manual.pdf.

[Mark-sf]

The belt should be 88mm in length. You can measure it by aligning it flat with just enough tension to have the two sides flat against each other and that should measure 44mm. One reliable vendor is here at https://www.beoparts-shop.com/product/platter-belt-3/ if it turns out your belt is over 1mm shorter. Also make sure that the pulley height is such that the belt runs fully on the subplatter.

[Mark-sf]

You are dealing with an AC Motor running off of the mains voltage, therefore there would only be mechanical speed adjustments and they would be in the manual. I would check that all of your play adjustments as per the manual are correct as there may be insufficient tension. All the above also assume you are not trying to use a 50Hz unit on 60Hz.

[Mark-sf]

That is fine. Check the spec for your cartridge as some need 1.2 grams.

[Mark-sf]

That relay is the stock one for 4002’s that have DC motors. Simply get the replacement kit for that type. If you want to experiment swap it with the muting relay as that one may be in better shape since DC does not flow thru it’s contacts.

[Mark-sf]

You don’t need to cut the mains. Simply carefully pick up the arm once it has moved to the record and move it back supporting it on any item that is high enough to keep the stylus from touching the top. You can also take the platter off and with the 45 adapter depressed press play and it will move over and lower.

Assuming the arm is truly lowered, then the weight should not be hitting the rear at zero grams as applying 1 gram is only 1/2 turn of the weight.

[Mark-sf]

The OEM relay is not available, but the replacement kits are readily on eBay depending on which relay you have. This is a DPDT relay that defaults to the 33 speed when unpowered. I would only jumper that side or remove it if you want to test 45 as well.  In any case, I would always replace it at this point as any cleaning fix is only temporary and the part is cheap enough.

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