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Beogram 4002: Restoration of DC Motor Video Published - Check It Out!

By popular request (really, I got quite a few emails about this!...;-), I finally completed my Beogram DC motor restoration video! It demon...

Monday, August 31, 2015

Beogram 4000: Restoration of a Seized Solenoid to Tonearm Linkage

It turned out that the linkage that connects solenoid mechanism and tonearm was seized in the Beogram 4000 that I obtained from the UK. This meant I had to take the sensor arm assembly out to extract the linkage that I could relubricate it. It turned out that the pin on which it usually rotates had seized in the linkage and that the pin was liberated from its pressfit socket in the sensor arm base. I made a video that explains the issue and shows how to repair it:

Saturday, August 29, 2015

Beogram 4000 Arrives From UK! Solenoid Oscillates!

I just received another Beogram 4000. This time from the UK. The unit is in decent condition, at least it has the MMC cartridge mount intact and the sensor arm insert is still there. The cueing/tonearm lift control panel came loose during transport. A great idea to tape them down. Luckily, the seller had the deck covered with a heavy duty plastic foil under the hood, so nothing bad happened. It will be straight forward to re-attach the panel.


Inside it seems everything is present:

But of course, like most units of this age it passed through some less-inclined hands and suffered a bit. I am not sure what attracts people to cutting off power cords, but this one, like the one I just obtained locally, had its power cord severed. So I bought a power plug and attached it to the cord:

Then it was time to plug it in. The first thing I usually do with a Beogram of unknown provenance, I measure if the voltage rails are present. At C1 one can measure the rectifier output for the 6V rail that drives the control system. It should be somewhere around 12V:

And on C2 one can measure the regulated 6V rail:

This looked pretty reasonable, so I went on to the 24V rail that is responsible for the power side of things. First I went for the rectifier output at C3:
And then for the regulated 24V rail at C4:
This seemed within spec, so these capacitors seem to have some remaining life left in them. I will exchange them anyway, but this was good enough for an initial turn-on of the deck.

I pressed the start button. Happy moment: The strobe lamp still works:

The carriage was also set in motion (good!), but then at the point where the tone arm should have been lowered into the lead-in groove of a 30 cm vinyl, a strange phenomenon occurred: The solenoid emitted a loud noise and its plunger oscillated rapidly. A 2 min video is more than a 1000 words, so I made one! Here it is. It demos the issue and shows how I repaired it.


Essentially, all it took to fix this was to reattach the lead that connects the emitter of TR4 to the current limiting resistor that is on PCB #7:






















Let's see what else this Beogram has in storage for the Beolover!

Thursday, August 27, 2015

Beogram 4000 Arrives! First Impressions!

Lucky Day!! Today a Beogram 4000 arrived in my driveway. It is a bit of a project, but came with a pristine MMC20EN cartridge (I am listening to Miles Davis 'Water Babies' right now with it! - Awesome!).

Also the exterior and the hood are in pretty good shape. And a really nice condition platter. Here are a few first impressions:

Nice control cluster (disregard the Sharpie marks under the position indicator for now...;-):

Lovely platter:

























Here comes the sad part: The sensor arm insert is missing and the cartridge mount came off with the cartridge. It was not taken off for shipping and probably took a hit during transport. Actually I did not know that it had a cartridge on there...anyway, now I am really interested in making my cartridge mount replacement part perfect...;-). 

In fact it is interesting to see how B&O designed these first mounts. They were done with flex board, very similar to my approach, and the plastic part was simply molded in a shape that 'bulged' the PCB a bit at the end of the mount to press it into the cartridge contacts. Later designs are based on metal contacts and a rubber sub-structure that also renders the mount contacts flexible. All this makes me hopeful that I really might be able to get this mount replacement part going. Now for the sensor arm insert, well, I guess a 551x might have to bite the bullet and take one for the team. The mighty 4000 has precedence!


A few more impressions...real expert work on the RCA plugs,

and also on the power cord. Did they think this is an electric lawn mower??

All in all, I'd say not too bad! I am looking forward to getting this baby going again!



Monday, August 24, 2015

MMC Cartridge Box: Another Iteration

This is a follow up to my recent post about the design of MMC20 and MMC4000/6000 cartridge storage boxes. I just received the next iteration from Shapeways. I changed the lettering on the covers and also designed a cover with a view port to directly see what type cartridge is inside. Here are a couple of impressions:

I also made the covers a tad thicker in the hope to get a tighter fit, but now they are a bit too tight for my taste. So, I guess the next iteration may be the final one...;-)


Sunday, August 23, 2015

MMC20 Cartridge Mount Replacement: First Design Iteration

A while back Sonavor posted some shocking pictures on his thread about Beogram 400x repair and restoration on Beoworld.org. He was about to finish his restoration of a beautiful Beogram 4000 and after having had to meet challenges like replacing the line transformer and the strobe lamp, the gods of vintage hifi gave him one last challenge: When he tried the deck out, the cartridge mount broke off, probably due the previous owner having cracked the small plastic tab that inserts the electrical connections into the cartridge body and also holds it in place. A typical B&O design: Very elegant but needs a refined touch to use it properly. Here are two of Sonavor's pictures after he extracted the broken cartridge mount after dipping the extracted arm into hot water for a while to loosen up the glue:




































Absolutely nothing one wants to encounter while working on such a beautiful design! He was able to fix it by extracting a mount from a lesser model, but we started wondering if these mounts can be reproduced with modern 3D printing technology. Obviously the contacts are the biggest challenge. It is interesting to see that in the 4000 they were formed by a flex circuit board that was integrated into the plastic part. In more recent models the contacts were actual Au coated Cu-Be tabs held in place with a plastic bar (see below).

Sonavor then sent me a spare tonearm with a loose mount giving me an opportunity to have a closer look (I was reluctant to extract the mount from one of my working turntables, as you can probably understand...;-). So I set out to build a replacement part. The first step was to make a model of the plastic part in CAD software and have it printed. I did that and yesterday I finally received the first iteration of this design from Shapeways. This shows the part (blue) in comparison with the original part that holds the cartridge:


I decided to go the 4000-way for the contacts using the flex PCB approach. This required to glue the board in place to the plastic part, which has a 5 mil recess to accommodate the board thickness (visible in the picture if you look closely). To achieve a good bond I designed a tool matching the shape of the PCB area. This allowed me to apply pressure to all parts of the PCB during the curing process:



I made a flex PCB with traces with the right pitch. The traces are 1 mm wide and spaced by gaps of 0.7 mm, i.e. the pitch is 1.7 mm. Here is a photo of the final board in comparison with the contacts on the mount:


Then I cut one of the strips to shape and coated the traces with solder. In the final version this will hopefully be an Au coating:

The next step was glueing it to the mount. I used standard epoxy. Superglue would probably be another option. My thinking was that epoxy is a bit flexible, giving this PCB a bit of leeway when someone sticks on a cartridge:
After 10 min holding the assembly (I will definitely design a second tool for the backside of the mount for the next iteration that I can use a carpenter clamp for that...;-) and cutting the traces to length the PCB was attached:


And assembled with the lower part of the assembly that features the grounding pin:


And here with cartridge :

For comparison here is a photo of the original part. A quite nice match!:

I evaluated the conductivity across the contacts. For both original and new part I measured a nice 770 Ohm across each of the coils, so that is pretty promising.

What was not promising that much was that the contact was a bit intermittent on one of the coils. This means I need to redesign the shape of the bump a bit that presses the contacts into the contacts on the cartridge. Also my parts was a tad to thick on the back end (3D printing is not an exact science (yet) and achieving a perfect fit is usually a trial and error effort needing a few iterations), and I had trouble sticking it into the arm all the way. I think I could force it in, but then that would not be Beolove!..;-):
After these tests, I replaced the cartridge a few times and after about 20 cycles one of the traces came off...this can probably be addressed by recessing the PCB at the tip of the mount to reduce the forces on the traces at the end of the board during the insertion process. On to the next design cycle.












Saturday, August 22, 2015

Beocord 9000: Rebuilding the Pinch (Rubber) Roller

The final crowning task to be completed on the Beocord 9000 that I am restoring right now was to rebuild the pitted and cracked pinch roller. Most of these decks have this issue. After all they are more than 30 years old! That is definitely exceeding the life expectancy of most rubber based products. I think a rebuild of the pinch roller is a must if one wants these decks to perform as new.

Luckily, there is Terry Witt at Terry's Rubber Rollers & Wheels. He is the world expert on rebuilding tape rollers and has a widely acknowledged authority on this topic...just visit some 'tape heads' blogs and chat rooms...;-). I think he does an outstanding job for an entirely reasonable price. So, don't bother buying second rate stuff on eBay with bad bearings and plastic wheels etc...just extract your original B&O quality rubber roller and send it to him! He is absolutely reliable and trustworthy! I made a short video about this procedure for the Beocord 9000. It shows how to get the roller out and put it back in. Enjoy!:

Saturday, August 15, 2015

Beogram 4000: Reservoir and Motor Phase Capacitors Replacement

I recently supplied a customer with reservoir and motor phase capacitors together with my 3D printed adapter for his Beogram 4000.

He reported that he was only able to measure half waveforms at the AC motor of his newly acquired Beogram 4000. This indicated issues with the phase capacitor or the power supply reservoir capacitors. He installed my kit and the problem was fixed. Here is the link to my original post about this procedure. Another Beogram 4000 back in service! He sent me these great pictures:

This shows the new capacitors and the red 3D printed adapter that holds them in place using the original mounting strap of the original, much larger, capacitors:

And here some impressions of the deck back in service. What a beautiful design!

 

 

 

Thursday, August 6, 2015

Beomaster 8000: Boxing Up for International Shipping

My experience with the shipping of Beomaster 8000s is such that one should basically never ship them single boxed (see recent single box mishap here). The 47 lbs weight of the units makes double boxing with thorough foam padding with industrial grade foam necessary. I use new foam and boxes whenever I build a shipping container. In fact, I am thinking I will refuse return shipping without a second box from now on. Single box shipping is penny-wise but pound-foolish. Maybe a $30 difference in materials. Yes, quality foam is expensive, but worth every penny if you Beolove your Beomaster 8000. Anyway, here we go:

International shipping requires typically a box with a smaller volume weight of 108 inches (i.e. circumference x length <= 108 inches). These parameters need to be kept in mind. Otherwise it will get complicated since either juicy oversize charges apply or freight must be used (depends on carrier).

Luckily the Beomaster 8000 fits into a 12x24x36 box with an inner box size of 10x20x30. Add two full size 1" poly foam sheets (~72" x 80") and a few scraps of cardboard for additional impact shields and we are good to go. Here are a few impressions of my effort with a Beomaster 8000 that I am shipping to the UK tomorrow:
I start out with a double strength corrugated cardboard 12x24x36 box. Then a foam layer:
Now it is time to place the inner box. Since I was not able to procure double strength 10x20x30 boxes, I put two single strength boxes inside each other. This creates a very HD inner box. Then another two foam layer into the inner box:
Now it is time to build the foam layers around the inner box. Two layers on the long and three layers on the short side.

I layer the foam with additional cardboard pieces to add more impact protection. It also helps to push the foam all the way down:



Now add a Beomaster 8000! A last look

And then it gets wrapped in a layer of thin cushioning:

After putting it in the inner box, more foam is layered around it. Two layers on the long sides and one on the short. So we have a pretty uniform foam layering on all sides once all foam layers are added up between the two boxes.
Now it is time to fill the wedge shaped space above the Beomaster:
Wait! I was able to supply a pristine looking Beolab Terminal remote for this Beomaster. 
Now is the time to add it. I cut out a window for it in one of the foam pads that go on top of the Beomaster:

And the final layers
and one more on top:


Time to close the inner box:

Add another layer of cushioning. Unfortunately, there was not enough room for a full inch of foam, so I had to use a 0.5" styrofoam panel. This should work.

Add a full roll of packing tape to protect the corners and seams, and an expensive international mailing label and customs forms in quadruplicate and we are good to go!

Farewell my lovely! May the postman be gentle with you! This is Beolove!


















Monday, August 3, 2015

Beocord 9000: Restoring the Peak Program Meters with SMD LEDs

I recently successfully rebuilt the broken (4 missing segments) Peak Program Meter (PPM) of a Beocord that I had received for some TLC. Since this procedure was straight forward and had a nice result, we decided to also do it for the other Beocord 9000 I am working on, which still had an original PPM with all the segments working. I initially did not want to touch its PPM since I had never done one before, so like any good doctor I aimed to 'do no harm', while surgery was not absolutely necessary.

However, since the technology is the same as in the 7-segment counter display it is likely that some of the segments would have broken in the near future. So, while I still have it on my bench I think it is a great idea to do it now that I know how to make sure there are no issues in the near future.

Here are a few impressions of the procedure on this unit. Please, check for details in my original posts (post 1, post 2, post 3). As a fan of 'kaizen' I made a small further changes to the process by adding some glue to the restored plastic discs that hold the PPM covers down.

The original PPM still installed:

After removal:

Removing the covers by gently prying off the small plastic discs that hold them to the PCB:

Now they come off:


 This time I also removed the light guide for the scale illumination. It comes off anyway when one cleans the PCB with ethanol after soldering:
Now I was ready for soldering the SMDs in. This shows the green ones lined up for installation:
This shows them all installed and ready for testing:


At this point I usually do a 24 hrs test to make sure they are all o.k.

Now it was time to put the covers back on. So I clamped the covers and the light guide down and then recreated some resemblance of the small plastic discs by pushing the remaining stubs down with my soldering iron set to 200C. That just softens the plastic enough to be able to press it flat:


After this I put some small drops of Aleene's glue on the areas


and let them dry. This glue can be removed after soaking in ethanol for a while, so this is completely reversible.

I think this is a pretty good solution, at least for the Beocords since their displays are tightly held in place by the bezel that gets clamped over them, i.e. even if one of the spots came off, the covers would not be able to fall off.

Then it was time to install the rebuilt PPM. This required replacing the original current limiting resistors of the segments with larger values to account for the much higher efficiency of the new SMD LEDs. This shows the original resistors:
And here the new ones:

And after installing the PPM across the resistors.

Then I gave it a spin with a standard 1Vpp 1kHz signal at the inputs and the recording volume slider set to ~6. That gave me a nice full range on the meter. Beautiful these big segments!

That is it. All we need now is the rebuilt pinch roller that will soon come from Terry's Rubber Rollers. Then this baby will be ready for prime time!