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Beolover SyncDrive: DC Platter Motor Replacement for Beogram 4002 and 4004 (Type 551x and 552x)

Late Beogram 4002 and the 4004 (Types 551x and 552x), which have DC platter motors instead of the earlier synchronous AC motors usually suff...

Thursday, December 29, 2016

Beocord 9000: Pulse Found...Beocord has life

Continuing on with the Beocord power checks today (yesterday actually now)...I moved on to the Beocord regulator board and power supply board.

The regulator board has the +5 VDC and ±15 VDC regulators. They are all mounted on the big heatsink in the back of the Beocord. I like to check the condition of the heatsink compound and the mica insulators to make sure things are not dried out. This Beocord looks pretty good.

I have seen other cases where the Beocord regulator board had deterioration of the mica insulators and dried out heatsink compound.

No problems with the regulator board so I moved to the power supply board to check the voltages there. After verifying the ±15 VDC on the board I discovered a 6.5 VDC line from the power supply board to the microcomputer/display board was missing. This measurement point (D15 cathode to ground) should have around +6.2 VDC when the Beocord is turned on (not in standby). Instead, I only measured 15mVDC.

I verified the problem wasn't with the regulator and power supply boards. The problem was coming from the destination. It was time to remove the front glass and control panel to look at what is going on. The schematic shows the 6.2 V from the power supply going to capacitor C56 on the microcomputer/display board. Being an electrolytic capacitor it is a suspect so I pulled it and it did indeed measure faulty.

This was actually good news. Electrolytic capacitors going bad are a common fault in old audio equipment. That is why recapping them is a pretty standard step on most restorations. In these Beocords however, the electrolytic capacitors are known to last a lot longer so they are not always recapped. I was wondering if a recap was in order for this Beocord and now I have my answer. I replaced the C56 capacitor with a new Nichicon 105°C capacitor and the Beocord came to life.

Play, Fast Forward and Reverse all work smoothly with this unit now. This is a good milestone to reach on the restoration.

As can be seen in the picture, the display is missing some segments. It should be displaying 06:25. That problem is also expected and the restoration will be to replace all of the original display LEDs with new SMD (surface mount) LEDs. I will also replace the other Beocord light bulbs with LED replacement assemblies used before on the Beolover Blog.

At this point in the restoration I haven't been able to check the Beocord audio output or record functionality. I will attempt to play the Beocord through an amplifier and measurement equipment tomorrow to see what the "before" scenario is like before doing the capacitor replacement.

Beogram 4000: Restoration of the Arm Lowering Mechanism, Replacement of Tracking Sensor Light Bulb with a LED Assembly, and a New Aluminum Pulley

I started working on the Beogram 4000 that recently arrived with a bit of shipping damage. The first order of business was to reconnect the ejected carriage to its linear rod bearings. This shows the carriage turned over:
and this shows the slide rod with the linear bearings that were liberated from the carriage assembly:
I removed the rod to get the bearings out. This shows them from the bottom:
They have a directionality that needs to be kept in mind when pressing them back into the carriage body. I did that with a big adjustable wrench:
After this procedure I was able to reinstall the carriage and start my normal restoration routine, which usually begins with the rebuilding of the arm lowering mechanism. This shows the solenoid and damper assembly with the connecting linkages and springs:
I removed everything
And spread the parts out:
After cleaning and lubricating I re-assembled the assembly and moved on to the next step, which is the restoration of the linkage between damper and tonearm. This linkage is often stuck or moves only reluctantly. This shows the arms from the back:
Two screws hold the sensor arm in place. After their removal the arm can be taken out:
I removed the linkage. As expected it moved with a lot of resistance and it was difficult to remove it from the pin:
After cleaning the pin and putting some fresh synthetic grease on it, I reassembled everything and adjusted the arm parallelism:
All good again in the arm lowering department. On to the tracking sensor light source. I usually replace the original light bulb setup with my 3D printed LED assembly to ensure long term stability. This shows the original setup:
I removed the bulb housing. This revealed the aperture that sits underneath and controls the light that falls on the light sensors below:
As expected the aperture was pushed to the left due to the shipping issues that reoriented the arms to the right. This will be rectified when I adjust the tracking sensor response. I installed one of my LED assemblies:
The final step was to install a new pulley. I use machined aluminum pulleys provided by Nick (I will be happy to get you in touch if you need one - just use the contact form to the right). This shows the new pulley installed:
Beolovely, I'd say! On to restoring the contacts that control the carriage movements, but that is the topic of the next post about this lovely Beogram.

Tuesday, December 27, 2016

Beocord 9000: Power Supply

 Moving on to the Beocord electrical problems I started with the power supply.  The power supply in this unit was having problems. I wasn't measuring +24 VDC on capacitor C1.  At first I suspected the rectifier board so I pulled it and examined the supply capacitors (C1, C2 and C3).  Here is the rectifier board in the Beocord 9000.

Here are the C1 through C3 measurements.

I decided to swap some parts with other Beocord 9000 units I have on hand. This Beocord's rectifier board worked fine in another, working Beocord unit I have so the board is fine. That led me to the transformer. Sure enough, the transformer was the problem.
At first I thought the transformer was defective so I started checking other Beocord 9000 units I have...both working and non-working. I found another one with a non-working transformer and compared the Beocord serial number to the one I am working on. What a surprise! I had another Beocord 9000 unit that was an assembly line mate to the current Beocord I am working on. What are the odds of that? After all of these years these two meet up on the same workbench.

The transformer turned out to be a non-issue as I remembered the transformer assemblies have an internal 250V, 0.5mA fuse inside. I opened up both transformers and sure enough, the fuses had blown.

This resolved the Beocord 9000 power supply questions. Now it is on to figure out why the unit will not come on.

Sunday, December 25, 2016

Beocord 9000: Finishing Up The Tape Transport

The Beocord 9000 tape transport repairs have been identified and fixed. I did some more cleaning and lubricated moving parts as I started the reassembly of the tape transport. Even though I don't plan on changing out the Beocord thrust roller, I disassemble that assembly as well to clean and lubricate the parts involved. Here is a picture of that step.

Here is the tape transport ready for reassembly.

The first item to go back in is the take-up reel and supply reel assembly. That is followed by the clutch assembly and the interconnecting mechanics.

After that is the flywheel and belts.

Finally, the cassette holder and the opening damper assembly.

Since the Beocord 9000 being restored isn't ready for any electrical testing, I pulled an older Beocord 9000 I have and swapped its tape transport with this newly restored transport. I inserted an old pre-recorded cassette (from 1972!) that I always seem to use as a tape transport functional test. It is amazing that it has lived this long without getting eaten.

For this first tape transport test I only tested Play, Fast Forward and Rewind functionality. What I am looking for here is that the Beocord tape transport motor, wheels and belts operate smoothly and don't stop unexpectedly.

One thing to note at this point - I see a lot of Beocord units of the 8000 to 9000 series where people advertise them as just needing new belts. While that is most certainly true, the replacement of the rubber wheels are just as important if the deck is to perform Fast Forward and Rewind functionality reliably. In my first Beocord repair of this type I did everything except the wheels and sure enough, the Fast Forward function was very unsatisfactory. Sometimes it worked sometimes it didn't. The reason was the worn rubber wheels.

The initial tape transport test was a beautiful success. I ran the tape forward all the way to one end, then did a full reverse rewind. After that I spot checked the tape play. Everything worked extremely smooth.

The next step in the restoration will be to examine the electrical problem with this Beocord.

Saturday, December 24, 2016

Beocord 9000: Identifying Repairs

The disassembly of the tape transport allows me to get to various nooks and crannies for cleaning and locate hard to see places that need repair. This makes sense from a restoration stand point but you pretty much have to disassembly a majority of the transport anyway to replace the rubber wheels.

NOTE: Don't disturb the part of the transport where the tape heads are mounted. Chances are they are still in alignment or, at least very close. There is no need to remove them at this point unless you know they are defective.

Here is a picture that identifies the four rubber wheels that will need to be replaced.

The replacement wheels and the rubber belts I will use are parts I get from Martin Olsen. He has done the research to make sure these replacement parts are accurate reproductions for the Beocord 9000.
Here are the replacement parts for the belts and wheels.

This picture shows the tape heads and the pinch roller (or thrust roller). The picture also shows what type of dust and dirt builds up inside these machines.

One of the rubber wheels to be replaced is part of the Beocord clutch assembly. Every clutch assembly from a Beocord 8000 to 9000 deck I have seen has cracks in the plastic where the pulley shaft mounts (via small brass inserts in the plastic).

I went ahead and disassembled the clutch assembly to apply the fix for the cracked plastic. I cut sections from a brass tube and epoxy into place so the brass sleeves prevent any more damage. The tubing I used is 8.73mm (11/32 inch) x 0.355mm (0.014 inch). I got mine at a hobby store that specializes in parts for remote control airplanes and cars. I used a Dremel tool to cut sections off then file off any burrs. When mounting the brass sleeves I remove the brass mounts the clutch shaft fits in to.

The final repair to identify is the repair of the tape head transport leaf springs. I already know there is one broken spring mount. I need to also check for any other places there are cracked or loose plastic pieces. I found these bad spots by the gears that dampen the cassette holder open/close function.

I will repair those spots with some epoxy when I fix the leaf spring mount here.

I wanted to get the epoxy step done and cured so I could continue with the tape transport. I actually did the cleaning and epoxy step last night so I could continue working today. This picture shows the re-installing of the leaf springs that hold down the tape head transport. Some new TriFlow Red Grease, the 2.5mm ball-bearings and the springs are complete. Next it is on to installing the new wheels and lubricating the moving parts. That should mean the tape transport will be ready to reassemble and test.

Beocord 9000: The Tape Transport

With the belt residue cleaned up, the next step in the restoration is to pull the tape transport out where it can be disassembled. There are three screws to remove and four connectors in order to remove the tape transport. Here is the Beocord tape transport removed and ready to be worked on.

Now it is on to the disassembly so I can clean, lubricate, repair and replace the rubber wheels.

Beocord 9000: Belt Deterioration

On any old audio gear that requires rubber belts to operate you would expect that changing the belts to be required for a restoration. With the Beocord 8000 through 9000 tape decks that is also true but typically that step has an additional step of cleanup of the old belts. Pretty much every Beocord I have restored has belts that have deteriorated to the point of becoming a sticky, gooey, tar-like mess. I guess it is because the Beocord was stored some place warm for a long period of non-use. These components, like automobiles, do not do well when not used regularly.

Here is a picture of the belt residue found in this Beocord. As I said, this is a very common situation to find. Cleanup involves tweezers, Q-tips, Kimwipes and isopropyl alcohol. I try to carefully pull out pieces of the belts with tweezers wherever I can. Otherwise, trying to grab the old belt pieces with a Q-tip or Kimwipe smears the belt into more cleanup. Pieces of the old belt can be found in various places inside the Beocord.

Beocord 9000: Opening It Up

The Bang & Olufsen audio equipment from this early 80's period are quite a joy to work on. The components open up into a nice service position where it is very easy to get to the internals for inspection and to work on.

On the Beocord 8000 through 9000 series of cassette decks one of the first things to check is the tape transport mechanism. Servicing will always require new belts of course but there are quite a few other things to do regarding the mechanics.

The first thing I saw when I opened up this Beocord 9000 was a loose part that had broken off the transport. The inset picture shows the little leaf spring. There are three of these springs that hold down the tape head transport as it slides forward to engage with a cassette. Without these springs the tape head transport can teeter up and down which would not be good for the sound. The red line shows where the broken spring should go. There was also a 2.5mm ball-bearing that is part of the spring assembly. That ball-bearing is gone but I have plenty of spares.

Beocord 9000: A Christmas Holiday Restoration Project

The Christmas Holiday season always allows me to try and squeeze in some extra audio restoration projects. Thanks to this Beolover blog I am going to document the restoration of a nice Beocord 9000. This restoration will be followed by a Beomaster 8000 restoration as the owner of these two components would like to get them back in full working order.

Here is what the Beocord 9000 looks like from the outside. The left side corner has a little bit of damage to the rosewood veneer but other than that it is in very nice condition.

Wednesday, December 21, 2016

Beogram 4000: A New Arrival from California with a Bit of Shipping Damage

A Beogram 4000 recently arrived for some TLC. Unfortunately, the need for it increased a bit during transport. When I took it out of the box I found this:
The carriage had liberated itself from the pulley which was stuck to some tape in the left back corner. Since the arms were held in place by tape the carriage was prevented from ejecting through the platter orifice and larger damage was prevented. Although the arms took a bit of a beating for that service. But I think this can be rectified. Another reminder that it is important to hold the carriage in place during transport with some foam under the hood and some tape across the arms cover. See my video that shows how to package the 4000 properly.

The arms cover was a little bent by all this:
Another concern when this type of event happens is the red position indicator, which is easily broken off since its narrow end is positioned inside a narrow slot under the keypad, which gives it only limited range to move:
Miraculously the indicator survived:
The rest of the Beogram seems in pretty good condition, so I am pretty confident that this unit can be returned to a fairly pristine state.

Tuesday, December 20, 2016

Beogram 8002: Glueing on the Aluminum Panels, Installing the Hood and a Test Drive with Chico Hamilton on Impulse!

Time to put this Beogram 8002 back together! It came a bit as a kit with the hood removed and the aluminum panels detached. As usual I glued the panel around the platter on with epoxy using 4-40 washers to bridge the gap between the plastic shell and the panel:
After the epoxy had hardened it was time to glue on the panel:
After this it was time to put the hood back on. It simply clips into place around the back part of the plastic shell of the enclosure. The only sweat producing part is to get the leaf spring inserted the correct way while attaching the hood. This shows how the spring is to be inserted:
since I only have two hands, I fixed the spring in place with some Scotch tape:
This helps a lot since the assembly is upright during this attachment operation. Once the hood assembly was in place it was time to attache the smaller aluminum panel.
As usual, I attached it with three layers of double sided tape. That shimmed it up to the level achieved with the 1980s style foam adhesive tape B&O used back then to attach these panels to the plastic parts.

After all this it was time to give this 8002 a spin. I selected a recently acquired original pressing of Chick Hamilton's gorgeous "Passin' Through" album (Impulse A-29).
The second side is an amazing, almost psychedelic experience that would probably convert the most ardent digital music purist that vinyl is the way to go! Such a direct, warm and vibrant experience! Absolutely amazing! I wish I could find a time machine and go see a Hamilton performance live in the 60s!