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
Yes, I verified with my DVM that the voltage switches on and off to the strobe via the relay. I also have a 27k ohm resistor inline with one leg of the strobe lamp path.
Thanks!
Tonight I had just enough time to check out some Beogram 4000 control panel functions. I opened up the control panel and check the switch leaf springs and cleaned them with some Deoxit. The slow forward and slow reverse functions were not working so I checked the motor voltage on those operations. The voltages were zero but all it took to fix them was to adjust the trim pots (1VR5 & 1VR6) for those functions. I adjusted the voltages to 3.0 VDC per the service manual. For a real detailed demonstration of this adjustment, check out Beolover's blog here.
Today I was going to mount the main board back into position. After I tried that, I noticed the platter motor didn't run. So I unbolted the board again and the motor started operating again. Experimenting with board positions and the motor operating/not operating, it appears the problem is in the wire bundle shown in the picture below. I can move just that part of the wire bundle and cause the motor to run or stop. I have some wire tracing and possible wire replacement ahead of me next.
It gets more and more interesting here, I had some similar problems with a Beocord 5000 pizzabox, turned out to be plugs-jacks cleaning, these low voltage connections are a PIB they dont burn through anything.
Collecting Vintage B&O is not a hobby, its a lifestyle.
I cut the bundling threads so I could separate and isolate the problem wire(s). I got it down to an orange and a red wire. When I traced the red wire, it went to the 0TR2 transistor (one of the output amplifier transistors to the platter motor). Pulling back the yellow insulators I discovered the problem. You can see in the picture below that the red wire is detached from the transistor and the other red wire is barely hanging on. Same with the blue wire. Maybe a previous owner replaced the transistor and didn't get the leads soldered on good enough?
With the wires re-soldered correctly, the motor is working again. I even get a little more amplitude on the sine wave...though still not up to the 6 VRMS I would like to see. The motor is smooth and quiet. Next step is to bundle the wiring back together and bolt down the main board.
I re-installed the main board to its four mounting posts and decided to do a first speed test. Up to now, all I have tested was that the platter motor turns with a good shaped sine wave and the frequencies of the sine wave were per the service manual. I had not tried the motor connected to the platter with a belt. Before going further I wanted to make sure the motor works good while actually spinning the platter.
Sure enough, the motor quietly drives the platter and the speeds are pretty decent. I played around with adjusting the speed fine tuning from the console and I am able to set the 33 1/3 RPM where is between 33.125 and 33.5. The 45 RPM seems more accurate. It varies between 45.025 and 45.25. I will come back to the speed checks later after I finish the tonearm adjustments. I am pretty pleased with this first check though. The speed variance is consistent with what I saw with my Beogram 4002 type 5503 (AC motor).
One more set of checks tonight...I verified the slide contact switches are in the correct position and function correctly. With a 7 inch record on the platter the Beogram detects it, switches speed to 45 RPM and attempts to set down at the start of the record. The set down for a 12 inch record looks good too. I think what is left are the platter leveling adjustments and various tonearm adjustments. There are also some electrical adjustments to check (diaphragm, differential stop and a revisit to the speed checks).This Beogram needs the phono cable to be reworked. It doesn't have the original DIN plug and the RCA jacks that are on the cable now don't look very good. I have a new DIN jack I can install but I will do that last.
Most impressive work and dedication John!
Your neon bulb should be with you tomorrow.
Jacques
Thanks Jacques. This has been a fun project. I knew it would be a long one going in but I felt confident with the support of the Beoworld forum.
Publishing about one's project gives us the boost to carry on, I find. This is essential for me, at least.
You did everything by yourself John! Almost 10,000 views, wow!
A goal of this thread was to show some details between the various 400x model turntables. I am hoping some of the problems I run into provide some solutions to other beo-virus infected people. Believe me, there will be plenty of kudos to send out when this latest Beogram is done. I have had a lot of help with this one.
I think the number of views reflects the popularity of the Beogram 400x series of turntables. The original design was magnificent and it still holds up today. That is quite a legacy of the Bang & Olufsen design team.
sonavor: I think the number of views reflects the popularity of the Beogram 400x series of turntables.
I think the number of views reflects the popularity of the Beogram 400x series of turntables.
Nah. Admiration of your talent and dedication.
This is a beautiful thread and I'm sure it will be useful and entertaining to many people in the future as well. Thanks for taking the time (undoubtedly quite a lot of time!) to post all these quality photos and information!
--mika
Have you seen Rudy's Beogram 4000 mods on his Beolover blog?
chartz: Have you seen Rudy's Beogram 4000 mods on his Beolover blog?
Yes, I sure have. I put a link to his blog on my posting above where I adjusted the slow tonearm speeds. His videos are excellent. Rudy is also becoming an expert in 3D printing of replacement parts.
I made some decent progress tonight starting with the mechanical adjustments. The first thing I did was work on setting the Beogram platter height. The procedure is pretty much the same as the Beogram 4002 platter height adjustment earlier in this thread. However, there are differences. The spindle bearing and nut are different on the Beogram 4000. There are three allen head bolts that lock the main nut in place to secure the bearing. Those have to be loosened to turn the nut if the bearing height needs adjustment (to raise or lower the platter height).Here is a picture of the bearing and adjustment nut. The relationship of the nut to the brass bearing in the picture resulted in the platter not sitting perfectly flat. The platter could tilt a little. When I adjusted the bearing during the procedure, I made sure the bearing was not flush with the nut. That resulted in my sub-platter resting perfectly flat without any tilting.
Here is the sub-platter mounted on the bearing.
The purpose of the adjustment procedure is to adjust the platter so the distance from the platter surface to the bottom of the detector arm is 13 mm. It needs to be 13 mm at the edge of the platter and the center to ensure the platter is level. I was lucky and this adjustment procedure went faster on this turntable than it did on my Beogram 4002.
Like the Beogram 4002, I set the tracking force by setting the dial to 1 gm, then adjusting the counter weight to calibrate it with my scale. This worked well before but caused a problem with this Beogram 4000 that I will show further down in the thread.
The next two pictures show the adjustment of the lowering height of the tonearm (with cartridge) to the platter.
Here's the bolt for controlling the lowering tonearm/cartridge height.
Before I try a record and go through the diaphragm adjustments, I rechecked and readjusted the tonearm assembly for parallelism to the detector arm and horizontal position to the detector arm. I am not real pleased with the adjustments on this that I made earlier in the thread. It doesn't seem like the distance between the tonearm release lever and the damper rod is correct. because of that, I also don't like the clearance of the tonearm release lever and the tonearm slide arm (D) when the Beogram is supposed to be playing a record. Here is a picture of the tonearm release lever and damper rod. There is too much space between them.
I was able to close the gap between the release lever and damper rod by adjusting the horizontal position of the tonearm (screw F). However, that leaves the tonearm height a little higher than the detector arm. That gives a little better clearance and resulted in the tonearm raising and lowering better than before the adjustment.
With the tonearm seemingly functioning decently, I continued on with the diaphragm adjustments. With these adjustments, the belt is removed from the platter and a record is turned manually while observing the tangential arm motor advancing the arm assembly. The service manual says when the arm is first lowered onto the record grooves, the record should rotate 4 +- 1 turn before the servo advances the arm. After that, the servo should advance at every turn.
I guess I'll have to finish posting the latest progress later after my last post has been moderated.
I'll have to post some pictures of all the different type of main bearings I have examples of for this 400x series.
On to the diaphragm adjustments. This procedure calls for removing the platter belt so the platter can be turned by hand. A test record is placed on the platter and the tonearm is lowered to some track. On first lowering the tonearm, the procedure says the record should rotate 4 +- 1 turns before the servo advances the tonearm. After that, the server should advance for each turn.
My Beogram wasn't advancing until six or seven platter rotations so I had to adjust some of the diaphragm controls. The trim pot that controls the lamp intensity helped some by increasing the detector light brightness. I eventually had to loosen locking screw "C", then adjust "B" to get the four rotation, servo advancement per the manual. The servo does keep up with the platter rotations after that but it doesn't do it after exactly one rotation every time. I am also unclear about the sixth step in the adjustment with says to - "make sure that the servo system does not regulate backwards until after the turntable has turned at least 10 cm backwards from the forwards regulation." and"To make adjustment if necessary, correct the spacing (1 mm) between the diaphragm and the photoresistor."It is difficult to measure the exact distance of the diaphragm from the photo resistor (with the black, plastic cover removed), but it looks like mine was at very close to 1 mm.
At the back of the service manual there is a section that talks about the addition of the trim pot to adjust the lamp brightness as a better way to deal with the sensitivity of the diaphragm adjustment instead of actually re-positioning the diaphragm.
At this point, with all of the necessary adjustments checked, I decided it was time to give the Beogram a first spin test. I connected the turntable up to one of my preamps and tried it out with an MMC 6000 cartridge. There was music! There was also a loud hum with the music but I expected that because the phono cable that is on the turntable looks in need of repair. At least I hope that is all it is. I'll find out later when I replace the cable.After playing with the turntable in operation I am not satisfied with the tonearm adjustments. The cueing is not quite right. Lowering of the tonearm works very good but when I have the tonearm lift up, I see a slight horizontal movement in the tonearm position. It should just go straight up.So I decided I have to re-adjust the tonearm settings again.Here is a picture of the first spin.
There are a few issues I have to correct with the tonearm.1. I don't like the gap distance between the damper rod and the tonearm release lever (too much space).2. There isn't enough space between the tonearm release rod and the tonearm bracket (D) that it releases.3. The top surface of the tonearm isn't horizontally aligned with the top surface of the detector arm.4. The tonearm counterweight assembly is too close to the tonearm pivot assembly.To fix all of those things I have to re-adjust at least five adjustment screws again. I actually removed the tonearm bracket D again and remounted it.
Here is the view of the tonearm after I corrected the tonearm counterweight position and the D bracket.Earlier, when I balanced the tonearm and calibrated the 1 gram setting with my force gauge, I didn't realize that positioned the counterweight assembly dangerously close to the tonearm pivot assembly. That affected the range of other tonearm adjustments. The D bracket of this turntable had originally been bent a little at the groove where it meets the lift lever. I had straightened that bracket because I think it should be straight. The manual doesn't call for bending it. However, that puts the end of the D bracket really close to the tonearm depth control bolt. To compensate for that, I had to put some spacer washers where the bolts mount the D bracket to the back of the tonearm. That, of course, affects the adjustment of the counterweight.
So many pieces affect each other. With the settings I made resulting in satisfactory clearance of the moving parts, I sacrificed having the tracking force dial reading exactly 1 gram when I have 1 gram of force calibrated. I had to do that so there would be good clearance between the counterweight assembly and the rear of the tonearm pivot assembly.Here is a picture that shows the gap I mentioned between the counterweight assembly and the pivot assembly. It also shows the clearance of the D bracket and the tonearm drop height adjustment screw. You can see that the tracking force wheel is at a higher point now for my 1 gram calibration.
The result of the re-adjustments are a good clearance of the tonearm bracket D and the tonearm release lever when the tonearm is released for play.The positioning of the tonearm release lever with the damper rod is also good now.
...and I am now able to have the tops of tonearm and detector arms align horizontally.
With those adjustments, the Beogram cueing now functions the way it is supposed to ... straight up and down.Now I need to replace the phono cable and hope that fixes the hum in the playback.
chartz:Yes, this is a little frustrating! It took me several attempts - and a lot of sweat - to correct that. Everything interacts with everything here... I too found the shutter's vertical position to be critical. The arms should indeed be perfectly aligned, another challenge this. A little unnerving all that. You'll sort it out John!
I think I finally have it adjusted Jacques. It does try one's patience. Once all of the adjustments are made though, they should be good for a long time.
sonavor: Once all of the adjustments are made though, they should be good for a long time.
Once all of the adjustments are made though, they should be good for a long time.
As long as you don't ship the deck anywhere