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Beogram 400x projects

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sonavor
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The last steps are to place the metal spring and bolt on the top plate. I did this procedure on all three chassis lockdown assemblies so they should all have equal distance of travel when I am adjusting the floating suspension springs.


sonavor
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This picture shows the mounts for the rear tonearm transport rail after I removed the two set screws. The front rail mounts are glued in place but I don't need to remove them. If anything I might need to add material to them to raise them up a bit. However, I am hoping that removing these rear screws will be enough to raise the front of the detector arm so it is level.


sonavor
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Sometimes some unusual repairs are necessary. When I removed the floating chassis I unbolted the voltage selector and fuse box. After the fuse box mounting screw was removed I noticed the mount for it was falling apart. So before I finish getting the suspension pieces all back in place to check the platter measurements, I will wait until tomorrow for some epoxy to dry sufficiently to reattach the fuse box.


chartz
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chartz replied on Thu, Jan 28 2016 6:40 AM

Thanks John, got that. I will check whether it's my problem too or not on Saturday and I'll get back to you. 

Jacques

sonavor
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I have most of the chassis reassembled now. Before I start in on the platter to deck alignment again I want to do some work on the wood trim. One of the few bad things about this second Beogram 4000 I purchased is the front wood trim is noticeably lighter than the sides. I don't know if it was replaced at one time or maybe is was in some cabinet where only the front got sunlight (and it faded). I am going to sand it down a bit and try Søren's Old English Oil trick to see if I can darken it. This might take five or six coats to work the way I want it to. If it takes too long I will continue on and work on the Beogram adjustment procedures without the wood trim and deck panels.


Søren Mexico
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Sand down all of it before you start tinting it, there may be less differences than you think

Collecting Vintage B&O is not a hobby, its a lifestyle.

sonavor
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Søren Mexico:

Sand down all of it before you start tinting it, there may be less differences than you think

Yes, I didn't forget your advice on the sanding.  Thanks.

Today I think I finally got the platter level across a plane that is 23mm down from the Beogram arms. After my changes to the tonearm transport rails and putting everything back together the detector arm horizontal level with respect to the floating chassis is really close.


sonavor
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Now it is finally time to calibrate the tonearm tracking force. I like to do this by setting the tracking force dial so it reads 1 gram, then I adjust the screw on the back of the tonearm to adjust the position of the weight until I measure 1 gram on my scale.


sonavor
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The next adjustment is the tonearm lowering limit. The service manual calls for approximately 0.5mm from the stylus tip to the top of a lower level platter rib.

Here are the before and after pictures of that adjustment. Tomorrow I will start in on the tracking adjustments and if all go well I should be able to finally try out how Beolover's replacement cartridge mount does.


sonavor
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Today I started to close in on the home stretch with this turntable. Another adjustment procedure that was necessary is the platter belt travel path. It was running too high on the motor pulley and every now and then I could detect it rubbing the underside of the platter. Adjusting the motor tilt screw clockwise I lowered the path of the belt so it is unobstructed.


sonavor
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It is finally time to adjust the record tracking of the tonearm. I posted pictures of this on the first Beogram 4000 earlier in the thread so there's not need to go into much detail again here. However, I will say that Beolover's replacement tracking lamp source with the nice Bourns 100 ohm trimmer works very well. This adjustment procedure takes a few iterations to get the tracking set but I think it is way easier than the platter height adjustment.


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The record tracking appears to be in adjustment now so I decided to go ahead and check a test record to see what sort of phono signal I am getting. I decided to use my MMC4000 cartridge and the B&O 3621003 Test Record. The first thing I wanted to check is that both channels have sound output and that the channels are correctly wired.
The test record track 5 is for channel identification so I played that track through a JEC phono amplifier to my audio analyzer. This allows me to see the playback on my computer monitor. Here is a picture of the results. I am just interested that each channel is producing output.


sonavor
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A side note: Here is my little JEC phono preamp for testing. It isn't a bad little preamp...not as good as my Yamaha C2a phono section but good enough for testing on my workbench.

One reason I bought it is because it has a DIN plug on the back for B&O turntables. As you can see I am not using that. I am using a B&O adapter to RCA jacks. When I first tested the channel identification I was seeing that the left and right channels were reversed. That didn't make sense because I traced my phono signals from the cartridge mount to the output terminals of the Beogram. I knew they were correct. So I plugged the Beogram DIN plug into a B&O phono converter, then connected the left and right RCA plugs into the preamp left and right jacks. The channel identification measurement came out correct. That means the DIN jack in the little preamp is wired backwards. I will have to open it up later and fix it.


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Even though I haven't made any final adjustments to the Beogram speed settings, I decided to play Track 12 of the B&O Test Record. That is the 3.150kHz WOW and Flutter Test. Both channels measured 3.2124kHz so the speed appears to be a little off.  I can't wait to get my hands on one of Beolover's high resolution turntable speed measurement tools.


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Although this Beogram still has a good number of steps left to complete before it can be added to one of my systems, I wasn't satisified with just looking at the phono signals on the analyzer screen. I wanted to hear some sound. So I rigged up the phono cable to my workshop Beomaster 4400 and played the first track of the B&O test record. Finally, sound from an actual record through the replacement cartridge mount, through an amplifier and to some speakers.

This Beogram's phono cable looks to be in good shape but it doesn't have an outer shield wire like my first Beogram 4000 unit did. Due to my BM4400 being kind of far from the Beogram I am not able to connect the phono cable directly. I have to run it through a three foot extension...which means going through a couple of extra connectors. There is some hum in that rigged up cable configuration so I will need to do a direct connection on the turntable connection to make sure it is okay. However, it is also shorter than my other BG4000 so I probably should plan on just installing a new phono cable. I think I have more cable and another DIN connector to make one.


sonavor
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One more play test tonight. I moved the Beogram to my office system and connected it to a Yamaha C85 preamp. That is the system I currently use my first BG4000 with (because it is the one I listen to the most). I played through Side A of James Gang Rides Again (original vinyl copy). The sound was nice but if I turn the volume up when no record is playing I can hear a little bit of hum in the speakers. So I will install a new phono cable on this Beogram and wire the shield wires like my first BG4000 turntable.


chartz
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chartz replied on Sat, Jan 30 2016 10:31 AM

Not sure where the hum comes from. All my BG are perfectly silent, so I can't advise here.

I checked the headroom of the suspension locking mountings, but they were perfectly adjusted already. 

On another matter, on my BG, the guiding front rail was already upped quite a lot with spacers (at the factory), so I've got no further possibility of adjustment. Like you, the arms are not perfectly parallel to the plinth/platter, descending ever so slightly towards the front of the deck.

I guess I'll leave it like that.

As a aside, I wonder whether the last ones delivered were as well manufactured and adjusted as the older ones. Just a thought.

Jacques

sonavor
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sonavor replied on Sat, Jan 30 2016 4:51 PM

Can you post a picture of the spacers on your front and rear rails sometime?  If you adjusted your platter for 23mm to the top of your Beogram arms and they are slanting down a little, then your platter is probably lower than it should be, right?

On my amplifier hum issue...looking at it fresh this morning I discovered it is a problem with my power amplifier. The hum is always there. I just hadn't noticed it before because you have to put your ear right to the speaker to hear it. When I have headphones to the preamp there is no hum coming from the Beograms. So I can decide to keep the phono cable on the Beogram after all (for now anyway).

Today I should be done with the wood trim piece. Then I will find out if this Beogram can be adjusted to have a flat platter and deck surface.

sonavor
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Today I installed the replacement lamps for illuminating the scale window. I used Beolover's custom LED replacement board. It is a direct plug in for the existing 12V lamps. The nice thing about the replacements is that they have been adjusted to produce the right, yellow tint to the glow so the indicators look original. This picture shows the new lamps along with my red LED replacements for the speed indicators. I adjusted the load resistors on those LEDs to get a glow that is the same intensity as the original lamps.


sonavor
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Here is what it looks like in operation.


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The Søren treatment on the Beogram wood trim turned out well. The top edge of the two side panels are just darker than the front panel. I applied several coating treatments on the top edge to darken it and I am satisfied how it turned out. There is just a blond streak in that top edge that will be lighter than the sides. On the front face I only applied one treatment of the Old English dark oil. The front and sides look the same shade to me now so I reinstalled the wood trim on the Beogram.


sonavor
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Next step was to add the Beogram deck pieces. My hard work of redoing all of the suspension appears to have paid off. Yesterday I was able to adjust the platter to tonearm height to the target 23mm distance. Today I was able to adjust the floating suspension so the deck panels are even with the platter surface. Between those two adjustments I don't want to count the amount of time it took (no hourly chart record like Søren recorded Smile).


Søren Mexico
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sonavor:
On the front face I only applied one treatment of the Old English dark oil. The front and sides look the same shade to me now so I reinstalled the wood trim on the Beogram.

to protect it treat it with boiled linseed oil, this will darken it a little, but protect it better than the Old English, no hurry, nothing happens to it within 6 month, but any water drops or greasy fingers will show and discolor the wood, Old English doesnt protect as good as boiled linseed oil.

Very nice looking deck my compliment for your thoroughness, patience and attention to detail, a perfect restoration

Collecting Vintage B&O is not a hobby, its a lifestyle.

sonavor
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sonavor replied on Sun, Jan 31 2016 1:34 AM

Hi Søren, that is what I meant when I posted that I applied the Søren treatment. After the last coat of the Old English dried I buffed the wood with a polishing pad and applied a coat of boiled linseed oil. I let that sit for a while before wiping off the excess. After that I let it dry overnight before lightly sanding and applying one more coat of the linseed oil.

Thanks for your wood restoration tips on your past projects.

Søren Mexico
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sonavor:

Hi Søren, that is what I meant when I posted that I applied the Søren treatment. After the last coat of the Old English dried I buffed the wood with a polishing pad and applied a coat of boiled linseed oil. I let that sit for a while before wiping off the excess. After that I let it dry overnight before lightly sanding and applying one more coat of the linseed oil.

Thanks for your wood restoration tips on your past projects.

 How I love to hear that, good job, I love wood

 

Collecting Vintage B&O is not a hobby, its a lifestyle.

sonavor
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It is time to finish up the bench adjustments on this Beogram and move it to my office where I can spend some time playing records (what it was meant for).
I did a quick verification of the stylus travel path. Eventually I would like to design and build a little jig that mounts on the parallel rails and can give me the necessary reference points to check things like the stylus path, arm parallelism and so forth.


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Next I decided to use the BG4000 built in strobe lamp and under platter markings to set the speed for 33 RPM and 45 RPM.


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To compare the speed now with the measurement yesterday I put the B&O 3621003 Test Record back on the platter and returned to the Track 12 WOW & Flutter test which outputs a 3.150kHz signal. With the speed adjustment per the Beogram built in strobe, the audio analyzer now shows a frequency of 3.1889kHz. That is down a little from yesterday's measurement of 3.214kHz.
 


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For my final adjustment before moving the Beogram to my office I decided to use the 3.150kHz test signal off the test record to adjust my 33 RPM speed.  I played the track a few times and adjusted the 33 RPM adjustment screw on the control panel until I measured 3.15kHz on my analyzer. That will do for that speed. I don't have a 45 RPM test record so I used my handheld strobe generator and my reflector record I have used earlier in this thread. The 45 RPM speed measured around 45.4 RPM.


sonavor
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During the analyzer measurements above, I switched my phono cartridge from an MMC4000 to an MMC20CL. The frequency measured the same (as it should). I noticed that the signal strength went up a little (more output) with the MMC20CL.

Before putting the deck panels back on the Beogram I checked the tracking weight again and it is still calibrated for 1 gram. Now I will be off to do some music listening.


sonavor
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When parents have a new baby they tend to take a lot of photographs. The scenario is similar when a vintage audio enthusiast completes a new project. I keep finding excuses to take pictures of the Beogram. 

The phono cartridge mount testing continues as I switched over to an MMC6000 cartridge. So far there have been no hiccups with the new mount. I have also been testing various semi-clear vinyl records without any problems.


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One goal of this thread was to show differences in the Beogram 400x turntables. As can be seen in the Beogram 400x evolution, there were gradual changes. The first BG4002 turntables (Types 5501 - 5503) still had the AC platter motor and the Wien-Bridge Oscillator. A question came up about the platters of the BG4002 Type 550x and the BG4000 platter. I think the BG4002 platter could be used as a substitute on the BG4000 if someone was in a pinch to replace one. The only real physical difference I can see is the BG4000 platter has the markings for the strobe. You can use the turntable without the strobe and it probably wouldn't be too hard to make a strobe marking sheet to attach to the BG4002 platter.

Here is a picture of the BG4002 Type 5503 and BG4000 Type 5215 platters side by side. The BG4002 platter does have six screws on the underside. I guess those are for attaching the top layer to the base platter. The BG4000 must have those joined by some other method.


sonavor
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Update and some rework.

After a week of listening testing and some audio analyzer measurements, some rework of my Beogram 4000 #2 turntable was required.

One lesson out of this is the Beogram 400x can actually perform pretty well even if it is out adjustment. This is why even a seemingly nice working Beogram should be service checked from time to time.

With this latest Beogram 4000 restoration I thought I had the tracking adjustments all correct and the Beogram was performing well. Checking some reference frequencies from some test LPs even looked pretty good on my audio analyzer. However, during the listening tests this week a couple of little things hinted that all was not perfect. First I noticed a little sibilance on some tracks, then I was surprised that a couple of brand new vinyl records had some "pop" and "click" sounds during silent passages. I verified the new vinyl was indeed clean by replaying the LP on a Beogram 8002. It played perfect. So I returned the LP back to the Beogram for another check. Watching the Beogram play the track in question I noticed that the stylus and cantilever had a lot of horizontal movement before the tonearm would advance. My other Beogram 400x turntables played the same track without this happening. On the good turntables the cantilever remains nice and straight as the arm navigates the record. So it was back to the bench for this turntable.

It took a couple hours to remedy the problem. The fix involved rechecking all of the arm measurements and adjustments. I made sure the arms were perpendicular to the transport path and parallel to each other. Rechecked the tracking force and set down height. Finally I reworked the tangential arm tracking. That meant taking the tracking source lamp off to look at the aperture again. What I discovered was the aperture plate was too low on the tonearm pivot post such that it was rubbing on the top of the plastic housing for the photo resistors. That was restricting the pivot of the tonearm and is why I observed the cantilever sometimes moving and not the tonearm.

The service manual calls for a 1mm gap between the aperture plate and the photo resistor housing. Once that was set and the tracking sensitivity tested, I replayed the vinyl record I found the problem with. Now the cantilever remains nice and straight and the Beogram plays beautifully.
Here is the service manual adjustment I missed. I am so glad I found the problem before putting this Beogram into regular service as that out of adjustment aperture was causing extra stress on the phono cartridges.


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Now that the Beogram 4000 #2 turntable is hooked up to a system for listening tests I can return the first Beogram 4000 turntable back to the workbench and see about installing a new strobe lamp. Earlier in this thread I got to the point where I was trying to determine the alternative circuit to provide a strobe lamp for this Beogram. The reason this is necessary is because the first BG4000 has a replacement transformer that doesn't have a 200+ VAC secondary which is necessary to run the original strobe lamp. My plan for a solution is to use a full wave rectifier, some resistors and some LEDs to replace the original strobe. The AC power will come from the 10 VAC secondary.

I cut a piece of project board to fit into the original strobe lamp socket. After that I followed Beolover's lead and used red/green LEDs so I could adjust the color to try and match the original neon lamp. The black wire is for the return, the red wire is for the red LED and the green wire is for the green LED.


sonavor
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The green and red wires will go to separate trim pots (5kohms). Those trimmers will adjust the LED color. The trimmers have a common node that connects to a 1kohm load resistor which connects to the positive output of the bridge rectifier. The black wire goes to the negative side of the rectifier. The two AC leads of the rectifier go to the 10 VAC supply voltage.


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The next step will be to mount the new strobe into the Beogram. The current strobe AC lines go to the 120 VAC primary. One side through a current limiting resistor and the other through a reed relay on the power supply board. I will have to cut those lines out and run one of the 10 VAC secondary lines to that reed relay, then on to my strobe lamp board. The other 10 VAC secondary will be wired directly to the new strobe board. This will allow the Beogram ON switch to control the strobe lamp. There is an existing mounting screw hole on Beogram chassis I can use to attach the strobe board to.


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Today I finally am able to install and test the new strobe circuit in my first Beogram 4000 turntable. I cut and glued down some Dura-Lar material to be an insulator for the underside of my circuit board. The mounting of the board should keep it away from the frame but I want to be careful and ensure nothing could short out. The small board with the LEDs was able to recess some more so the original lens cover could mount to the lamp holder.


sonavor
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The next step was to tap into the 10 VAC, 60 Hz secondary wiring and route one lead through the reed relay on the power supply board that engages when the turntable is turned on.


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The 10 VAC power for the strobe circuit connects to the board via a small connector I added. Everything is now in place to see if the new strobe lamp comes on when the Beogram On button is pressed.


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Hurray! The circuit works.


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