Beogram 4002 Success! (and tips!)

[jacope]

Hello all,

About 8 months ago I picked up a BG4002 on eBay that had been incorrectly listed as a TX2 for $85 – SCORE (I thought).

Initial inspection (forgot to document as I went, so this is from memory and I cant guarantee 100% accuracy) :

I found that it is a type 5511 which is a european model with EU plug (I am in US) and some previous owner had chopped the din cable and installed female RCA jacks in the back of the chassis. The dust cover was extremely scratched with large gouges, and the wood frame was also rough. There were obvious signs of water damage with water stains and rust sopts internally – luckily no signs of water damage to the actual electrical components so that seems lucky. The PCB near the solenoid that routes signal to and from the tonearm area was shattered and sloppily repaired in the past. Attached MMC4000 had no cover or stylus.

I flipped the voltage switch to 110v and when holding start the motor would spin, and the 33/45 relay would immediately click to 45. When I released start, the unit would immediately shut off.

 

I started with some preventative maintaiance: replaced all electrolytics and tantalum capcitors, and all trimmers. Replaced large motor capacitor with new part from Beolover. Cleaned and lubricated all moving parts including tonearm solenoid area. Used some paper strips and deoxit D100 to clean the buttons and switch contacts. Replaced both belts. I also replaced the motor bearings with freshly lubricated bearings from DKsoundparts (not a small task!).

Now that I had a clean slate, I was hoping to have a working unit – pressed start and… no change. Bummer. Time to dig in.

First I wanted to see why the Start button only worked momentatily, so I took a look at the area around TR11-TR15 that deals with the button controls. Turns out TR12 and TR13 were both shot. Replaced the original BC237 with BC337 which did the trick.

Now I looked into why the tonearm motor was not running. I removed the motor and applied voltage and found that it was functioning but running backwards even with correct polarity. Strange. I found that with 13.5v applied it would not run hard enough to move the carriage. I swapped a working motor from another unit and it ran the carriage no problem. Bad motor, a relatively expensive part! Installed a new replacement from Beolover. Now to why the Beogram wasnt running the motor. I found that the motor was not receiving the correct voltage from the board, and then found that TR20 and TR22 were shot. Replaced original BC142 cans with 2N5320.

Now over to why the unit switched to 45 RPM immediately. First I removed RL1 and cleaned the contacts. This solved the issue but now I was not able to switch between 33 and 45 with the buttons. Taking a look around that area I found that IC2 was shot. Tried replacing with some alternatives I had on hand but none did the trick. Had to order an MPS A13 as was the original.

Unit now switched between 33 and 45, but the 33rpm bulb did not light. Removed the small board and found that the 33 bulb was blown, AND one of the wires had broken off. Replaced bulb and fixed wire.

Now my main issue was that the ^/v button did nothing at all. IC4 was not passing correct voltage to the solenoid. I found three issues and fixed all three, not sure if one or all fixed the up/down issue. First, the bulb that tracks the horizontal movement of the tonearm was blown, sensor was fine. Replaced bulb. The LED that fires through the clear plastic piece was blown no contact, causing havoc in that circuit. I ended up replacing the whole board with a new one from Beolover. Next and most strange, the previous owner had replaced 8D1, originally an OA91 germanium diode, with an IN4002, which is not even close to the original. He had also installed it backwards which will obviously cause problems. Replaced it with an IN933 which is a closer match.

I checked the orignal owners work on the RCA jacks, and found that he had shorted the capacitor between ground and chassis. Solved this and stripped and re-soldered the wires. I have plenty of other Beograms with DIN connections so I kept the RCA mod.

 

FINALLY after a lot of work and a lot of time searching and waiting for parts, I had a working unit. Adjusted all trimmers to spec, made a few small adjustments to the platter and tonearm, and could get to some cosmetic changes.

The aluminum strip on the dust cover is stamped “Beogram 4002” on the left and “Bang and Olufsen of Denmark” on the right. I wanted to use an original strip because replacements have no logos on them. I had a donor cover from a 4004 which only has the right-side logo, which was acceptable. Removed this donor strip with a heat gun. Removed original dust cover from hinge section by peeling back the edges of the aluminum to reveal four screws. Attached a new amber-color dust cover (technically for BG4000 but I like how it looks) from DKSoundParts to original hinge section and attached donor aluminum strip with 3M 300LSE .75″ double sided tape. The tape was slightly too large and I had to trim with a razor blade.

Finally, I carefully removed the old wood trim from the metal brackets and cleaned the adhesive with goo-gone and elbow grease. To a new walnut trim piece from Beolover, I attached the two metal brackets one at a time using JB Weld, paying very close attention to level and alignment. Take photos of the original to reference if replacing the wood trim. If I were to do it again, I would use a less rock-solid adhesive, perhaps something more pliable when dried.

Moved my MMC20EN to my Beogram 8000 and set the 4002 up with my MMC20CL, and all is well! Very happy with how it turned out, it was very daunting in the beginning.

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