Beomaster 8000: Installation of New Keypad Ribbon Cables

I recently received the lower front panel of a Beomaster 8000 for the installation of new keypad ribbon cables. The original ones had developed some bad contacts in the attached headers.

I designed proper replacements and had them custom manufactured:

I extracted the original ribbon cables and installed the new ones:

Then I open up one of my Beomaster 8000s and tested the keypad with the new cables:

Beolovely!! All keys worked as they should and so hopefully this restoration will come to a successful end soon!

MMC20 Cartridge Mount Replacement: Gold Plating of Contacts

I had some fun last night with learning how to coat the contacts of my MMC20 mount reproduction part with gold. This is a follow up to this post. I think naked copper traces are not good enough for long term stability on this part due to oxidation issues. I used an electroplating solution soaked wand and 4.5V DC with the negative lead connected to the traces to be coated (metal ions are positive) and the positive to the wand. After a few minutes working the wand I saw a golden sheen on the copper...this picture shows the coated traces in comparison with some uncoated ones:

After this success I studied up a bit more about gold plating and it seems that the microelectronics industry standard is to put a nickel diffusion barrier between the gold and the copper...I guess I need to get some Ni electrolyte going. I also need to test for adhesion, there are some interesting test procedures for meeting the electronics industry standards. But I guess I am one step closer to the final design!

MMC20 Cartridge Mount Replacement: Third Design Iteration

This is a follow-up to my initial posts about the design of a MMC20 cartridge mount replacement. The first design iteration is discussed here and the second one here. The result of the second iteration was pretty close as in that I was able to stick a cartridge on it and that the base fit into the arm tube of a Beogram 400x. The issues with V2 were that the angle at which the cartridge mounted was about 4 degree off and that the cartridge was a bit loose. Furthermore, the nylon based print was too flexible. 

Version 3 shown here uses a different, stiffer material and I changed the geometry a bit to ensure proper mounting angle and a tighter cartridge fit. Here are a few impressions:

The mount now fits with a decent press fit into the arm tube (I did have to sand it slightly - a concession to the still imperfect printing tolerances at Shapeways). It also looks fairly original, although the material is a bit rough in difference to the original injection molded plastic:

The good thing is that the tab is invisible once the cartridge is mounted. Here is a picture of the fit:

Quite prefect now, I would say...After I stuck the cartridge on I measured the coil resistances while wiggling the mount a bit. It seems the contacts between mount and cartridge are now stable!

To get this ready for prime time, however, I still need to learn to gold-plate the Cu strips. Another point is to find a more perfect way for glueing the contacts PCB. Beolove springs from continuous improvement! But I am fairly positive now that this design is getting pretty close for some in-situ testing.

Beogram 8000: Adjusting Horizontal Parallelism and Glueing the 3D Printed Plastic Tabs to the Carriage

The Beogram 8000 seems to like its new 3D printed plastic tabs that I implemented a few days ago. So I decided to epoxy them in place for long term stability. To be able to clamp them I needed to remove the tonearm carriage from the rail that I could turn it up to apply the clamps:

After applying epoxy to the remaining 'stumps' I clamped the new tabs in place:

After 5 min the epoxy had settled, and I took the opportunity to also adjust the horizontal tonearm parallelism. The adjustment screw can only be accessed from underneath the carriage, so this was the moment:

After adjustment the tonearm was at the same height as the sensor arm:

Lovely!

Beogram 8000: Repair of Broken Off Plastic Tabs on Tonearm Carriage with a 3D Printed Part (II)

Allright! After fixing the broken off tab on the rear of the tonearm carriage of the Beogram 8000 that I am restoring right now, I came up with a similar fix for the broken off tab on the front. This one was a bit easier to access:

I decided to design a 'cap' that would fit on the remaining stump and hold the carriage down on the steep rod on which it travels:

This part was more challenging to print since on one side it had to be very thin to not alter the 'home' position of the carriage, and due to the oval orifice for the rod. Such structures are difficult to print due to th unavoidable gravitational forces that make it difficult to bridge voids with the printer. That is why the part looks a bit 'wobbly'. These pictures show the part installed. Here without steel rod:

And with steel rod in place:

The rod is easily taken out from the plastic receptacles that clamp it in place on either side, i.e. the part can be installed by removing and then inserting the rod into the part, and then clicking the rod back into its receptacles.

I ran the mechanism a few times and it seems to work very nicely...the part does not obstruct anything in the motion path of the carriage. So potentially this is fixed. Like with the tab in the back I had to iterate the part a bit until a good fit was obtained:

I will epoxy the part into place once I am certain it performs well. Without clue it would probably not stay in place during transport. 

Beogram 8000: Repair of Broken Off Plastic Tabs on Tonearm Carriage with a 3D Printed Part (I)

I finally got back to the Beogram 8000 that recently arrived from Japan. After fixing the spindle rotary encoder issue, I had to put this project on hold to complete a Beomaster 8000. One of the remaining major restoration tasks was the repair of the broken off plastic tabs that hold the arm carriage to the metal rods on which it rides. They must have broken off during a rough transport experience or a similar stressful moment. Anyway, there was not much choice other than replacing the carriage with one from a donor 8000 or going creative on this issue with a 3D printer. I chose the latter since I usually cannot accept Beograms being parted out.

This picture shows the broken off tab in the back of the carriage:

and the photo below shows the other broken off tab in the front of the carriage. The white stuff is evidence that someone tried to glue the broken off part back into place, but it must have come off again:

The repair of this one will be the topic of my next post. Here is a picture of the second tab in the back that was still in immaculate condition:

It was immediately clear what was missing from the broken off tab: The part that swings underneath the rail rod on which the carriage travels. This keeps the carriage on track even if gravitational forces are briefly suspended during transport etc...

Gluing the broken off parts is futile in such cases. There is no plastic glue that can be strong enough to fix this type of issue. There is just too much torque on the part, while the contact surfaces are really skimpy and no match for the acting forces. So I set out to design a creative solution based on a 3D printed part. This is what I came up with:

The small tab clamps into the gap below the tone arm counter weight and holds the part in place. The bent section of the part goes underneath the rail holding the carriage in place. Here are two pictures of the part installed:

The part clips into place with a solid click and pretty much holds itself in place without the need of glue etc...I will nonetheless glue it once I am confident that it does its job well, to make sure that the Beogram survives its return journey to Japan. It is a pretty interesting process to design such a custom part since it needs to fit an already existing part precisely. This required a number of trial and error iterations until a satisfactory fit and a happy 'click' were achieved. Here is a picture of all the iterations that I printed before I had the one that is shown installed above:

If you look real close, every one is different. A lot of effort, but now the carriage of this Beogram is again held in place safely! At least in the back, the repair of the broken tab in the front will be the topic of my next post.

Beomaster 8000: Repair of a Ripped Off Keypad Ribbon Cable

I recently repaired a ripped off ribbon cable in a Beomaster 8000 that connects the volume rotary encoder to the microcontroller board. I thought I was done, but the front panel came back, now with the frequency encoder cable broken off. The hot glue that I used to fix it in place had come off from the cable, and subsequently it broke off during the rigors my customer's restoration effort put on the solder points:

At least this time I was able to reuse the cable in its full length, so I could simply remove a bit more insulation and solder it back in. I removed the keypad PCB, cleaned the solder points and then did the soldering:

Then I glued it on with epoxy to the PCB back, hoping this will be more durable:

After that I reattached the PCB using new (they should not be reused after taking them out) 3mm retaining clips and nylon washers to protect the PCB. Then it was time for testing. I put the panel into the Beomaster 8000 that I am currently restoring for another customer and turned it on. I tested all keypad buttons and both encoders, and everything seemed to work properly. I hope this was the last time I worked on this particular panel and this 8000 will finally be happy!

MMC20 Cartridge Mount Replacement: Second Design Iteration

This is a follow-up to my initial post about the design of a MMC20 cartridge mount replacement. In the meantime, I acquired a Beogram 4000 with a broken off mount, so now this is 'personal'...;-). Ouch!:

I just received the redesigned Version 2 prints from Shapeways. The main issue with the initial version was that the back part would not fit on the lower part of the original mount that will be reused, and that the contact tab would make intermittent contact. I realized that the issue was the 'bump' that I designed into the tab to press the contacts into the cartridge contacts. One I looked at the broken off tab of my Beogram 4000, I saw that a simple straight shape should work. So version two of my design aspires to closely resemble the 4000 version of it.

Here are a few impressions. Along with the changed shape, I also needed to redesign the tool bodies that are used for pressing the circuit board into the mount while the glue dries:

Hers is a picture of the curing process:

And here the result in comparison with the original mount (this one is from a later Beogram and was supplied by Sonavor (Beoworld)):

Then I tested it on a MMC20S cartridge. It made good Ohmic contact and I measured the usual 770 Ohms per coil:

This iteration now fits very well on the lower (original) part of the assembly:

Consequently, the part also fits into the arm tube:

However, the mounting angle is a bit too steep. From the gap, using a protractor, I deduced that I need to reduce the angle by about 4 degrees. Oh well, back to Autodesk Inventor for Version 3.  While I will be waiting for the Version 3 prints I also need to figure out how to plate the PCB traces with gold to ensure long term stability. We do not want to have oxide layers getting in-between our precious vinyls and our ears...;-)

Designing a new part: Quite a laborious process - A resuscitated Beogram 4000: Priceless! This is Beolove!

Beomaster 8000: Test of Repaired Front Panel Ribbon Cables

After reattaching the severed ribbon cable of the Beomaster 8000 front panel and cleaning the contact pads of the program and source keys, I tested the panel in one of my own Beomasters. It worked nicely, all buttons responding precisely and the rotary encoders doing their job. Here a couple of impressions:

Time to send this panel back that it can continue serving in its own Beomaster!

Beomaster 8000: Repair of a Broken Off Keypad Ribbon Cable

I am assisting a Beomaster 8000 restoration. Today I received the front panel of this unit with an almost completely severed keypad ribbon cable. These ribbon cables easily break off if the Beomaster is opened a few times. Often the glue that fixes the cables to the keypad PCB fails at this age and the 24 gauge leads take the brunt of the cable flex every time the panel is lifted. They only survive this a few times and then they break off. If only one or two break off, this can be fixed by inserting a bit of copper braid and with some flux and solder the connection can usually be restored. However, in this case most of the leads were broken off:

So it was time for some microsurgery. I removed the PCB. This required to cut the original retaining clips, which are of the non-removable type. They can easily be replaced with 3mm retaining clips, so this is not an issue. There is an earlier blog entry that details this procedure.

Once the board was removed, I cleaned up the solder points and then prepared the cable. I had to extend the length a bit since I needed some 'meat' to rebuild the connections. If the cable is too short it is difficult to put the panel into service position with connected ribbon cables. I made eight extensions from an old computer ribbon cable:

Then I soldered them to the prepped ribbon cable leads:

A bit of shrink tubing of the proper color finished the job:

Then it was time to solder the ribbon cable back in:

I also embellished the leads of the other ribbon cable with some solder to stabilize them. They were still intact, but I could see that they also had started breaking off.

Since I was in there, I decided to also clean the contacts of the keypad switches. They usually are a bit oxidized. The oxide layer can easily be removed with a fiberglass pen. This shows the P7 switch before cleaning:

And after:

I did the same with the contact springs. this pic shows one before. The dark spot is the oxide.

Unfortunately, I forgot to take a picture of the cleaned spring pad. They also get nice and shiny after the fiberglass pen treatment.

Then I put the PCB back in using 3mm retaining clips and #4 nylon washers to protect the PCB:

Then it was time to glue both of the ribbon cables to the PCB to protect the cable leads from further bending events. I used hot glue (like the original setup):

That should do it! 

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!