ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Turning down the red in the red/green LED gets a closer match. I will most likely test mounting the prototypes in the Beogram to verify how the strobe looks through the actual view window. I will have to do a little rewiring on the power supply board to route one side of the signal through the reed relay that originally passed the 200 volts.
Now that I have my LED strobe prototype working I am reluctant to pull my Beogram 4000 out of everyday service to test it out. It took such a long time to get the Beogram into operational state that I have been using it everyday...to much satisfaction I must add. But I will get back to the replacement strobe later this Summer. Right now I am refurbishing my Beosytem 5500 and 5000 components so my workbench is rather full right now.
-sonavor
I know the feeling. Enjoy!
Jacques
The last half of 2015 has been a long hiatus from my workbench for me. Too many other things have kept me away. I was supposed to have worked on a few Beogram 8002 (and 8000) units but there has been no time. It is now time to make some time and my second Beogram 4000 unit has jumped to the front of the line. I picked this unit up from a seller here in the USA but I think it was probably brought over by an individual rather than sold here. The AC plug looks like a DIY replacement.
This second unit is in nice shape. There isn't any dirt or grime to clean off. Perhaps it was serviced before.
The transformer looks original but slightly different than the original transformer of my first BG4000 unit.
The wood trim is intact. No dents or chips.
The control panel board and main board are very clean.
The tonearm assembly is in good shape.
Not surprising, the phono cartridge mounting tab is broken on this turntable. That is probably the reason the previous owner sold it.
The broken phono mount tab is the exciting part about this restoration. In my first Beogram 4000 I repaired the broken mount by stealing the phono mount from a Beogram 4004 spare unit (it was not in working order). For this repair I get to be the test subject of Beolover's re-manufactured phono mount. He has been working on a 3D printed replacement for a few months and just sent me the first one that is ready for a real world test. It was tricky for him to get the phono traces attached securely and here is the result. Very impressive don't you think?
The replacement phono mounting tab is for the top part of the two piece, clam-shell assembly the Beogram 400x tonearm has. I will re-use the bottom part of the clam-shell assembly from the Beogram 4000 original part. Beolover's part will mate with that to provide a new cartridge mount. No more having to rob a part from another Beogram.
Another Beolover reproduced part I will install in this Beogram is his PCB with LED and trimmer for the tonearm tangential drive detection.He has successfully used this part on several of his restorations so I am confident it will do the job here.
That part will replace the parts shown circled in this picture.
Next step is to take inventory and see if I have replacement capacitors and trimmer resistors in stock for this restoration. I may have to make a run over to Mouser for some parts.
Great stuff, it looks like a fairly unmolested example! I'm keen to see how Rudy's cartridge mount works out - I've been following his development posts with interest as my 4000 has the all to common issue also!
I still need to finish inventory on my replacement electronic parts but I do have to order a few capacitors.In the meantime I decided to go ahead and start with the removal of the broken phono cartridge mount.The first step after opening the deck up for work is to remove the single, small screw that fixes the tonearm to the swivel assembly. You take the screw out and gently slide the tonearm forward.
Here is the attachment hardware removed in taking off the tonearm.
There is enough slack in the phono wire where the tonearm can pull completely off the wiring board. One more piece of mounting hardware must be saved away somewhere safe...the flat mounting spring.
Since I will not be reusing the phono wires that travel up the tonearm to the cartridge mount I clipped them off instead of desoldering them for now. It will be easier to desolder the stubs later. It also provides a nice picture to label the wires.
Now for the fun part...boiling the tonearm. I dip the tonearm into the boiling water for a few minutes before attempting to push the phono cartridge mounting assembly out using a long screw driver. The hot water treatment by itself doesn't always work so I let it boil a couple of minutes longer, then pull out the tonearm and pop it into my freezer. After a couple of minutes in the freezer I try to push the cartridge mount out again. This time it only took one boil and freeze cycle for the mount to pop out.
Here is the cartridge mount assembly removed. The broken part of the black plastic tab finally broke off during the boiling water process.
Here are the old and new cartridge mount parts laid out together.
Time for a test fit. I won't press the new cartridge mount assembly all the way into the tonearm until new wires are attached and I am sure the position of the mount is perfect.
My MMC 20EN test cartridge seems to fit nice and snug onto the new cartridge mount. I think this replacement will work well. Tomorrow I will solder on the new wires for the cartridge mount, install it in the tonearm for good (I hope) and reassemble the tonearm.
Tonight I cut and soldered on the new 32 AWG phono wires to the cartridge mount. After soldering and checking the solder joints I added a dab of Aleene's glue to use as and extra strain relief to the solder joints.
I also replaced the ground wire with a new one. I'll let the glue dry for a while and put the cartridge mount together tomorrow.
The wiring of the two cartridge mount pieces is complete and now joined. I used my test MMC20EN cartridge to guide the assembly. Once this step is dry I will place the cartridge mount back into the metal tonearm.
Time to reinstall the phono cartridge mount back into the tonearm. I did another test fit to see how snug the mount is without any glue. It was pretty snug but I still felt it was necessary to precoat the inside of the tonearm with some Aleene's Tack It Over & Over glue. I used some heat shrink tubing to make it easier to control the phono wires during the process.
I kept the phono cartridge on the mount when I reinstalled the mount into the tonearm so I would get the exact depth necessary for a perfect fit. After the mount was in place I gave it a few minutes for the tacky glue to set up before removing the phono cartridge. The results are what I wanted so the next step is to attach the phono wires to the small board in the base.
These are the DIY threads that I love, expertly building a new cartridge mount (3D printed details from BeoLover), very small details to work on, only possible with a great amount of self confidence and know how. Cant wait to see what more you will bring to us John
Collecting Vintage B&O is not a hobby, its a lifestyle.
Thanks Søren. I thought I had better show more steps on this Beogram since it is the first time doing a tonearm repair with a remanufactured cartridge mount. Maybe some people will be able to suggest some easier steps. For now it is the hardest part of the restoration and I wanted to get it done first since without this repair...this turntable would never be able to function.
To complete the repair on the tonearm the final step is to reattach the arm and wiring to the tonearm base. That means removing the tonearm transport assembly from the chassis so I can turn it over and get to the right and left channel positive cartridge leads.I removed the four screws and plates that hold the metal rods the tonearm transport rides on. I also removed (not shown) the plate that holds the springs for the slide contacts.
With the tonearm transport assembly turned upside down I can get to the left and right positive solder points on the small solder board at the base of the tonearm. This board transforms the phono signals from the larger 32 AWG wire to the very thin magnet wires that fit down through the tonearm assembly pivot.
Now to trim the 32 AWG phono wires and tin the leads for mounting on the small transfer board. These small wires are not the easiest to work with (especially stripping the insulation). I'm glad I'm not working on a Beogram 8000 repair. The BG8000 runs the tiny magnet wire all the way to the phono cartridge mount. Those tiny wires are not color coded so you would have to really take care in getting the right lead connected.Here is a picture of the tonearm all wired back up. After soldering the red and white wires on the underside, I flipped the tonearm assembly over and soldered the remaining wires. I spliced the ground wire as I didn't want to risk damaging any of the small magnet wires that are in and around the ground wire solder point.
Besides the small wire soldering I think the hardest part of the repair is stuffing the wires into the tonearm while sliding it back into place on the tonearm base. I got it done and the leaf spring in place too.
Here is the tonearm assembly back together again. Now this feels like I am at the true start of the Beogram 4000 restoration. The broken cartridge mount is repaired so now it is on to taking apart the other mechanical pieces for cleaning and lubrication. The electrical restoration should be replacing the electrolytic capacitors and trim pots ... unless there are some surprises for me. I sure hope not.
The next steps in the restoration are to clean and lubricate the mechanical parts. After that, the capacitor and trimmer replacements. Once the electrical restoration is complete I'll go through the service manual electrical and mechanical adjustments.This Beogram 4000 is really quite clean. The mechanical parts also move very easy so it is possible it was serviced once or twice since it was new. It is tempting to skip the mechanical cleaning and lubricating step and go right to the electrical work. The problem is when you purchase a piece of audio equipment this old from a seller that does not know the history of the unit, you have to assume the maintenance work is due. Since the tonearm assembly is already in service position (off the rails) I will take out all of the mechanical pieces like the damper, solenoid, fixed arm and levers for cleaning and lubrication.The first thing is the damper piston that controls the tonearm raise and lowering lever.
The damper cylinder is held in place by two screws and is easy to remove. I cleaned it with mineral spirits then applied some silicone grease. The small, odd looking, silver screw controls air into the piston. Removing it allows the piston to be removed easily. Later, during the turntable adjustment procedures, the screw will be used to control the tonearm lowering speed.
I removed the tonearm raise/lowering control solenoid. This picture is after I cleaned the solenoid rod with mineral spirits and lubricated it with silicone grease.
I eventually got a stripped and cleaned tonearm transport.
With the fixed arm removed I am able to lubricate the tonearm lowering lever pivot point. Now I am glad I went ahead and did these mechanical restorations. This picture shows what you can find even if the parts appear to be in working order. The pivot post and lever is being held in place just by the wire spring with the clip. There is supposed to be another spring with a snap ring over the pivot post. Somewhere along the line somebody lost those pieces off this turntable.