Beogram 4000: Replacing the Keypad Light Bulbs with LEDs

The next step of my restoration of the Beogram 4000 that is on my bench right now was to replace the light bulbs in the control panel assembly with LEDs. I like to do this to increase the longevity of the unit and to guard against shipping issues. Incandescent light bulbs do not like vibration...Here is a picture of the opened up keypad:

The two bulbs at the top end are the bulbs that illuminate the unique position indicator feature of the Beogram. The vertically implemented bulbs below illuminate the RPM trimmers. I recently developed SMD LED based PCBs that replace the two position indicator bulbs (these parts are available - just send me an email). This shows the boards before installation:

The RPM trimmer bulbs can be replaced with standard red LEDs and current limiting resistors. Here is a picture of the implanted LEDs:

And after starting up the Beogram:

The position indicator LEDs are red-green LEDs tuned to appear with an incandescent sheen. This ensures that there are red photons to properly illuminate the red scale indicator.

This shows the LEDs at work after closing the panel back up. The red indicator is missing, since I did not reinstall the panel since I still need to restore proper functionality of the keypad switches. The unit has some issues with the slow scanning functions, which is an indication that the switches are corroded.

Very beautiful! What a nice design.

While I was in there I also glued the strobe light mirror back on (it often does off at this age):

On to the keypad switches!

 

Beogram 4000: Lubricating and Adjusting the Solenoid to Tonearm Linkages

After installing a working solenoid and removing the alien voltage regulator from the Beogram 4000 that I am currently restoring, I tested the arm mechanism, but it was still a bit sluggish. This  suggested that the connecting linkage between damper and tonearm lift needed lubrication. Also the horizontal parallelism of the tonearm was grossly out of whack. I tried to adjust this with the set screw in the connecting arm on the back of the tonearm counter weight, but this screw was epoxied in, preventing the insertion of a screwdriver...another result of Mr. Handyman's restoration efforts, I guess. 

This shows the back of the tonearm assembly:

First I took the connecting arm out and extracted the set screw by heating the arm with my rework hot air blower:

After removing the set screw:

While I had the arm out I also installed a nut and a washer on the screw that holds the arm counterweight to replace the locking ring that is normally installed. This allows to fix the zero-weight position in place by tightening the nut for much better long-term stability (and survivability during shipping):

After installing the arm back and adjusting the set screw properly the arm was horizontal and aligned with the sensor arm as it should:

Then I took out the sensor arm assembly to extract the solenoid to arm linkage:

I recently made a video that shows in detail how to do this procedure. The difference here was that the linkage was not completely seized to its pin, and that the sensor arm could be moved a bit forward easily after removing the screw that holds it in place:

This is important to give the linkage a bit more room when it is pushed out from its pin. There is a possibility to damage the wiring that goes into the sensor arm if this is not done. After removing the locking washer and the spring underneath (careful here...this spring can jump off if one is not aware), I lifted the linkage out

and cleaned everything. Then I added a bit of silicone grease to the pin and put everything back together. After installing and aligning the sensor arm assembly, the tone arm snapped into place as it should when rotated horizontally out of its rest position. Also, after trying out the mechanism by pressing ON revealed a smooth operation of the arm lift. This hopefully concludes the tonearm mechanism restoration.

Beogram 8000: Adjusting Horizontal Parallelism and Glueing the 3D Printed Plastic Tabs to the Carriage

The Beogram 8000 seems to like its new 3D printed plastic tabs that I implemented a few days ago. So I decided to epoxy them in place for long term stability. To be able to clamp them I needed to remove the tonearm carriage from the rail that I could turn it up to apply the clamps:

After applying epoxy to the remaining 'stumps' I clamped the new tabs in place:

After 5 min the epoxy had settled, and I took the opportunity to also adjust the horizontal tonearm parallelism. The adjustment screw can only be accessed from underneath the carriage, so this was the moment:

After adjustment the tonearm was at the same height as the sensor arm:

Lovely!