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
Here's a more detailed shot.
It turned out to be easier than that. No need to disconnect anything from the board in the previous picture. Partially removing the tonearm reveals another small PCB that changes back from the small phono wires to larger ones out to the cartridge. The Beogram 8000 ran the small phono wire all the way to the cartridge.
Here is a picture of the tonearm hardware that had to be loosened and removed to get to the wiring board in the arm.
Here is the tonearm removed.
Now it's time to boil the tonearm. I could make a joke about my wife being thrilled I was helping out in the kitchen but it is Mother's Day today so I won't.
The Beogram 4000 tonearm took more than just boiling to remove the cartridge mount. After trying a few times boiling, I put the tonearm immediately into the freezer for a couple of minutes. After the freeze treatment, the cartridge mount popped right out.It is similar to the Beogram 8000 cartridge mount as it is a clamshell design but it is a little different. The Beogram 8000 mount looks like it would work in this tonearm though. I'm not 100% sure I'm going to use the Beogram 8000 cartridge mount in the 4000 though. There is a chip in the mounting tab on the BG8000 and I'm don't know if I want to go to all this trouble and not have a unblemished result at the end. I am going to dig out my Beogram 4004 parts unit later and see what shape its tonearm is in.
For now, I have the Beogram 4000 tonearm ready for repair.
I dug out my spare parts Beogram 4004 unit and removed the tonearm. To extract the cartridge mount I decided to try a different heating method instead of boiling water. I tried a heat gun. Bad idea as it is more difficult to regulate the temperature. One reason I tried that was because I thought I might be able to salvage the mount with the wires intact. I was able to extract the cartridge mount anyway but the lower part got slightly deformed. The wire insulation melted in some spots as well.
That was lucky it was only the lower part and not the upper part (as that is the piece I really need) that got deformed in the heat.
Continuing on with what I had, I used the BG4004 top part cartridge mount paired with the BG4000 bottom part. For them to mate properly I had to file some ridges on the front half of the lower mount. The nice thing about this paring is that the cartridge mount looks like the original.
Here are some pictures of a test fit with an MMC cartridge.
I will still have to rewire the cartridge mount terminals back to the board that transfers the signals to the small gauge phono wire (that takes the signals through the arm pivot hardware). I'll have to order some wire for that as the smallest wire I have in stock is too big.
Tremendous work John. Please take many more pictures and measures so that a 3D repro part can be contemplated. I am confident it will be done, and we won't have to find donor units any more.
Jacques
Looking back, I think it is a good thing that the cartridge mounting tab on the Beogram 4000 broke when it did (while I am still working on the restoration). I would have hated to have completed the turntable and had it in use, then have the tab break while changing out an MMC cartridge. The tab was already on the brink of failure so now I can address it and get it fixed properly.Yes Jacques, looking at the two molded plastic pieces that make up the cartridge mount, I think it could be a good candidate for a 3D part solution. I'll talk to Rudy some more about it. I didn't really like stealing a part from another turntable either.
sonavor: I will still have to rewire the cartridge mount terminals back to the board that transfers the signals to the small gauge phono wire (that takes the signals through the arm pivot hardware). I'll have to order some wire for that as the smallest wire I have in stock is too big.
What size(s) wire(s) do you need?
I ordered some 32 AWG wire in various colors last night. This is the first time I have had to do any wiring at the tonearm level so I never had bought any that small.I hope to have the tonearm reassembled and working this weekend. Of course it will mean going through a bunch of the tonearm mechanical adjustments again. That shouldn't be too bad though.
sonavor: I ordered some 32 AWG wire in various colors last night.
I ordered some 32 AWG wire in various colors last night.
All right, but next time - and this goes for anyone - my shop WASTES more wire in a day than most people will ever need. If you - or anyone - needs a bit of wire don't be shy about asking me if my shop has any.
Sure thing Rich. I will remember that for next time. Thanks!
Some good news...I was able to recover my MMC 6000 cartridge that had the broken tab from the BG4000 tonearm. Per Søren's suggestion, I used a little heat on a tiny metal pin to create a channel into the broken tab. I had to be careful not to damage the cartridge. Once that was done, I was able to use the smallest, flathead screw driver I have to pry the tab back out. I tested the cartridge in a BG4002 and it still works so no damage to the pins.
Tonight I got the new tonearm wires attached to the new cartridge mount.
After soldering the wires I glued the two cartridge mount halves together and have them clamped tight right now as they dry. I needed to glue them together so the top and bottom pieces wouldn't slide at all. After test fitting cartridges on the mount, I decided there was a best position for the halves to mate and I didn't want to lose that. Tomorrow I will re-insert the cartridge mount and wires back into the tonearm.
With the cartridge mount put back together, I test fitted it in the tonearm. I guess because these two halves weren't originally together, the piece would not slide back into the tonearm. So I used a small file and carefully (and evenly) worked over the plastic piece until it could be pressed snuggly into the metal tonearm. It was still a tight fit but I could still pull it back out. On the test fit, I left enough out so I could remove it. On the final install, I used a small amount of Aleene's Tack It Over & Over glue. It provides enough resistance so the cartridge mount will remain in place but doesn't permanently bond with the plastic.After I set the cartridge mount in place, I did a test fit with an MMC cartridge.
I think the fit is as good as I can get it with the new cartridge mount. Now it is time to reconnect the tonearm wires with the main harness.
Finally I have the tonearm reconnected to the pivot assembly. I wish this meant I could jump back to the point I was at when the cartridge mount broke. The Beogram 4000 was just about ready to put back in use. Now...after disassembling the tonearm to repair it, I will have to start over with all of the tonearm mechanical and electrical adjustments.
Wow. Seriously, dude. Amazing work. I get to use that phrase again: Steely-eyed Missile Man!
I very much look forward to your report when you can actually play a record with this table! Hopefully that will be in the next few days. I'll be off the grid until Tuesday, but I will be watching this space when I get back!
VERY nice Work !
Martin
Thanks for the kind words guys. I appreciate it.
This is a four day weekend for me so this morning I was able to get right back to the Beogram. Indeed, most of the previous adjustments were all off. The only adjustment that was still intact was the turntable height (the 13mm from platter deck to detector arm). Because the tonearm was removed, I had to check the tracking path of the stylus (the tonearm length). My jig isn't built yet so I used a technique our friend Søren Mexico suggested - use some string.
I also had to recalibrate the tracking force. In this recalibration I was able to set the force wheel to 1.0 gram and make my adjustment.
The lowering depth had to be adjusted again.
Of course the servo control tracking diaphragm adjustment had to be made again. The lamp housing had been loosened during removal of the tonearm so it had to be checked. As expected it was off so I went through the adjustment of the diaphragm position and lamp intensity so the tonearm servo begins to advance after four platter turns (to begin with) and one turn (thereafter).This gets me back where I was when the cartridge mounting tab broke. I couldn't wait to try out playing an LP so I connected the phono cable DIN jack to my Beomaster 4400 and threw on a copy of Humble Pie "As Safe As Yesterday Is". Success! Left and right channels are clear and sound great. The album tracks good and the pickup at the end worked as expected.
I also tested a 45 RPM single successfully.
The 45 RPM single I tested with had a pretty narrow run-off track and the track barely finishes before the tonearm lifts and returns. I tried to run the Adjustment of Differential Stop procedure in the service manual (4-8) but it is not clear to me how to set up and execute it. To attempt the procedure I placed a record on the turntable and started playing the last track near the end. I ended up monitoring the motor voltage with my DVM but couldn't determine the 1.8 volts mentioned in the procedure. In the end, the way I made the adjustment was to use a few 45 RPM singles and an LP to adjust the trim pot 1VR4 until I was happy with the Beogram detecting the end of the record (and lifting off).
Here is a picture of my probe set up for measuring the tangential drive motor. They have to be placed where they won't interfere with the platter as it rotates.
Here is a picture of the 1VR4 trimmer for adjusting the differential stop.
I went through the service manual page 4-3 adjustments for the solenoid controlled contact switches - F (solenoid current limiter switch), D (tracking enable switch) and E (audio muting switch). Beolover has a really nice video on making these adjustments on his blog here. My Beogram required adjusting the muting switch a bit as it was disengaging a little late. I also set the gap on the solenoid current limit switch where I could tell it opens. I'm not sure it is 1 mm so I'll have to go back and check it again.
John check your PMs
Collecting Vintage B&O is not a hobby, its a lifestyle.
I am going to start putting the Beogram 4000 back together now so I can put it to good use in one of my systems. My plan was to replace the original Beogram 4000 white wood trim with a nice, perfect rosewood trim piece off a 4002 series. I had bought this spare rosewood trim a few years back to have as a spare. Unfortunately, even though I had examined the two trim panels together before, I hadn't looked closely enough. While the overall size is the same, the Beogram 4000 trim piece has three mounting tabs that are in different locations than the 4002 trim piece.
Here is another angle showing where the BG4000 and BG4002 wood trim panel is different.
The reason for the trim pieces being different on the right side of the turntable is due to the control panels being different and the aluminum trim panels being different sizes.
The trim panel issue doesn't change anything regarding keeping this Beogram 4000 and using it in my system. It is just slightly disappointing that I don't get to use the nice, spare rosewood trim. The original Beogram 4000 trim will need some restoration though. I can fix the small chip with some filler. Repainting is a slight dilemma. The white color looks aged so I will need to figure out a shade of white to repaint with. Another option would be to just paint it a different color. I am guessing the original options for the Beogram 4000 trim were rosewood, teak and white. Were there any versions in black?
I realized there is a better solution. I can use the good rosewood trim piece. By applying heat (from my heat gun) to the inside, metal frame of the Beogram trim piece, the glue that holds it melts away and I can (fairly) easily pull the metal frame from the wood trim. That means I can mate the metal trim frame from the Beogram 4000 with the rosewood trim of the Beogram 4002.
The heat gun and metal scraper worked good. The mitered ends of the wood trim did not appear to be glued together. The wood was glued to the metal frame and that held everything in place. I now have Beogram 4000 metal frame pieces and rosewood outer trim pieces ready to assemble. I will need to finish cleaning old glue remnants off first. After that I will need to select a good glue to use in putting these pieces together. I guess some sort of contact glue where both pieces are coated?
sonavor: The heat gun and metal scraper worked good. The mitered ends of the wood trim did not appear to be glued together. The wood was glued to the metal frame and that held everything in place. I now have Beogram 4000 metal frame pieces and rosewood outer trim pieces ready to assemble. I will need to finish cleaning old glue remnants off first. After that I will need to select a good glue to use in putting these pieces together. I guess some sort of contact glue where both pieces are coated?
When gluing wood to metal (steel) or plastic I use Gorilla glue white the contact glues are messier to work with and difficult to apply evenly
Søren Mexico: When gluing wood to metal (steel) or plastic I use Gorilla glue white the contact glues are messier to work with and difficult to apply evenly