Beogram 8002 From North Texas: Replacing the electrolytic capacitors

Moving on to the electrical tasks on this Beogram 8002 project...
There are electrolytic capacitors in the Beogram 8002 in four locations: the floating chassis, PCB 1, PCB 2 and inside the transformer box.  Typically not all of them will be out of tolerance but it is a good move to replace all of them rather than wait for them to fail one at a time. 

I will start by showing the replacement of the two capacitors on the floating chassis.
These two, 0C1 and 0C2, are part of the Beogarm 8002 +5 VDC regulating circuit.

The two capacitors are easy to get to although the yellow, black and blue wires should be disconnected and moved out of the way first.

On this project the Beogram 8002's owner had already purchased a capacitor kit for it. The kit contains most of the capacitors I normally replace and they are good quality capacitors so I will use them.

Here are the new new 0C1 and 0C2 capacitors installed.

PCB 1 is the main board of the Beogram 8002 while PCB 2 piggybacks on top and inside a shielded, metal box.  

PCB 2 houses the Beogram 8002 microcomputer IC and has just one electrolytic capacitor to replace.
It is a difficult one to deal with though.  The negative lead side is soldered to both the top and bottom layers of the board. In addition, the space is a very tight fit and is right next to the microcomputer IC.

This lone electrolytic capacitor, 2C28, is for the +5 VDC supply voltage to the microcomputer IC...so pretty important :-).

  
























I like to cut the exposed leads on the 2C28 capacitor to remove it first, then desolder and remove the remaining parts of the lead once I have more room.

This photo shows the other side of PCB 2 and the other two solder points of 2C28.

A number of years ago we started replacing the 40-pin IC socket for the microcomputer device on these Beogram 8000/8002 restorations.  Removing the old IC socket provides more operating room and the new 40-pin socket with tulip style contacts is a sturdier part than the original socket. It provides some extra insurance in reliability and is easy to replace during this capacitor replacement task.

The new 2C28 capacitor is in place and so is the new 40-pin IC socket.

I re-inserted the microcomputer IC (while taking electrostatic precautions of course).
I will apply new thermal paste to the top of the microcomputer IC later when I re-install the metal lid that has the heatsink for it.

One other step I performed on PCB 2 was to use a soldering tool to reflow the solder joints on all of the board connectors.  We have found that those connector-board solder connections can become faulty over time and they are not something a visual inspection can always catch. It is safer to just reflow the solder.

In case any Beogram 8000 owners are wondering, the microcomputer IC in the Beogram 8002 and Beogram 8000 are not compatible. The PCB 2 board and housing look the same but the functionality of the microcomputer IC itself is different enough where they are not interchangeable.

Next is PCB 1
I used this photo above but I will include it again.  The photo shows all of the PCB 1 electrolytic capacitors that will get replaced except for the one hidden underneath the metal shield box.  I will show that replacement capacitor a little later on.

As I said earlier, not every electrolytic capacitor in the Beogram 8002 will be out of tolerance but there are always some that are...

Both of those capacitors are part of the Beogram 8002 power supply circuitry.

The largest capacitor, 1C27, which is for +15 VDC supply filtering was still in tolerance but it is being replaced now while all the other work is being performed.

1C27 is a little unusual in that it has a three prong base for its negative lead.  The three prongs are for mechanical support and I have never found a modern replacement for this type of packaging.
The new capacitor is the common, two-lead, through-hole style of capacitor.

The Beogram 8002 PCB 1 board expects the 1C27 capacitor base to connect two of the board ground connections via that three prong base.  That can be accomplished with a jumper wire on the trace side of the PCB 1 or I can pop off the three prong base from the original 1C27 capacitor and re-use it.
I like to opt for the second option.

The new 1C27 capacitor positive lead goes right in the center of the three-prong mounting ring.
The negative lead gets bent around the mounting ring and soldered to it.

That is it. 
The new 1C27 capacitor will fit into the original PCB 1 holes and soldered in place the way the original was.

Here is that PCB 1, C28 capacitor that is underneath the PCB 2 shield box.

On PCB 1 on the other side of the shield box is 1C4.

That accounts for all of the PCB 1 electrolytic capacitors.

Just as I did on PCB 2, all of the PCB 1 board connector solder joints were re-flowed with solder.

The last electrolytic capacitor, 4C1, is a non-polarized capacitor located inside the transformer box.
The modern replacement capacitor is much smaller in its physical size so we created a 3D printed mount for it.

While I have the soldering tools out I took the opportunity to replace the audio muting relay on the Beogram 8002 output board, the small board that the 7-pin DIN connector is mounted to.

This is another precautionary change.  We have seen enough of these relays start to fail where it is safer just to replace them rather than wait for them to fail.

Here are the before photos.

I am including a picture of the trace side as it shows all of the wire connections for the phono audio signals.  The connections look really good on this Beogram 8002 output board. The last two Beogram 8002 output boards I worked on required re-soldering of those wires because they were poorly soldered and the connections were failing.  I expect the output board to always look like this one.

Here is the new Omron relay installed.

In the next post I will lubricate and re-install the tonearm assembly.

Texas Beomaster 8000: Sorting out problems with the microcomputer board

In the blog post where I checked out the Beomaster 8000 power supply I used a spare microcomputer board to run the Beomaster. The reason for that was because the original microcomputer board was not in good shape. During the recapping of that board I could see there were problems with it.

In this post I dig into the original microcomputer board with the goal of cleaning up bad solder joints, investigating some unusual board wiring and making sure the two processor devices are working.

The starting point of this task is with the recapped microcomputer board.

On the trace side the picture below shows this microcomputer board compared with a typical Beomaster 8000 board...in this case the microcomputer board from the Canada Beomaster 8000 unit.

The orange and green connection wires are what I expect to see on these boards. The other wires on the Texas Beomaster 8000 microcomputer board are unusual.

Checking them against a known good board I found that they do connect points that are supposed to be connected. The question is why and if they are necessary.  I started by removing one end of each jumper wire and testing if the connection was still good. In some cases it was so the wire really wasn't necessary. In several wires however the jumper wire was the only thing making the connection.

My suspicion is that board vias (connections between the top and bottom board layers) are not making contact.

Some of the jumper wires appear to have been made as a change to the normal wiring between vias on the component side.

One task on this board restoration is to replace the two crystal oscillators as I did on the Beomaster 8000 from Canada. Starting with that task will give me better access to board vias I want to resolder.

The following pictures show the removal of the two processor devices and the replacement of the crystal oscillator devices. The same care was taken regarding static discharge and the shorting of the oscillator leads while handling the processor devices.

When removing the processor chips I felt the sockets were showing their age so I removed the original sockets and plan to replaced them with modern, tulip style sockets. The pins are sturdier. This picture shows the old sockets (in the rear) and new sockets in the foreground.

While the processor devices and sockets were removed I installed the new crystal oscillators and added three jumper wires (blue, green, orange) between board vias as shown below. That is the normal way the Beomaster 8000 microcomputer board makes those connections. That eliminated three wires that were on the trace side of the board.

I also resoldered the vias involved in all of those connections.

After this first round of work I was left with the following...The green and orange jumpers that should be on the trace side plus three additional jumpers that I found I could not remove yet.
Note that the green and blue jumper wires were white wires earlier. I changed them when I started cleaning up bad solder connections. I did the same thing with the original yellow jumper wire.
I changed it to the white in the photo below.

Testing this state of the board resulted in a partially working Beomaster.

The standby LED dot illuminated and the keypad selection switch put the Beomaster in the power on mode. However the source selection did not appear to function and some displays were not working.
I swapped the two processor devices with some spares I had to make sure the processor chips were not the problem. It doesn't appear to be an issue with those two devices but I need to make some additional checks.

My prime suspect at this point is still connections between board layers. I want to see why those remaining three jumper wires have to be on the trace side.

For the green and blue wires (from two vias next to one of the oscillators) ... to IC7 I discovered that the board vias were the problem.

I removed IC7 to get to the component side of those vias and resoldered them there. I also resoldered the vias on the trace side. That resulted in those connections being good without the jumper wires.

Here is the original state of the microcomputer board trace side compared to the current state.
Note again that I changed the yellow jumper wire to a new, white wire when I cleaned up the ugly solder joints for that.

I am left with just the white wire jumper. That jumper is connecting the board ground between two devices (IC5 and IC6). With the wire removed those two points are not making a good connection.  The wire shouldn't be necessary so there is another via or two I need to check.

In this current state the microcomputer board still isn't functioning correctly. I can control quite a bit of the functions. The volume and tuning dials operate. The channel balance control works as do filter and tone control switches (for the three illuminated lamps below).

There are a couple of things I need to do next.

I want to put the original processor devices in one of my good spare boards to be 100% sure those devices are good.

I want to try and eliminate that grounding layer connection the white jumper wire is trying to do.

If finding and fixing the problem (that requires the white jumper wire) doesn't result in a fully functional microcomputer board then I will have to move forward on this project with one of my spare microcomputer boards and return to this problem board at a later date.

This microcomputer board is the only component in this Beomaster 8000 that is keeping it from moving to functional testing.

Beogram 8000: Replacing Capacitors On The Main Boards

Restoration work on this latest Beogram 8000 project begins with the main boards. I will replace all of the electrolytic capacitors with new, high quality, Japanese 105°C capacitors. Most of the time I use Nichicon, Panasonic or Elna capacitors. Where possible though I use WIMA polyester capacitors where capacitance values are 4.7uF or less.

Here is the main board with the microcomputer board and two small B&O mod boards attached.

The most time consuming PCB work is on the microcomputer PCB. There is only one electrolytic capacitor on that board but it is in a difficult place. Here is the microcomputer PCB opened up.

The 47uF (C28) capacitor has its positive lead soldered on the trace side of the board while the negative lead solder point is on the component side of the board. This capacitor is for the +5 V power supply to the integrated circuits on this PCB.

 I usually replace the microcomputer IC socket while I have that board open. The original socket is not as rugged as the modern socket I replace it with so it is a good upgrade.

Here is the microcomputer board with its new C28 capacitor and microcomputer socket.

NOTE: Because the microcomputer IC had to be handled I made sure to wear an anti-static (ESD) wrist band.

Now it is on to the main board. I start with the three largest capacitors - C27, C24 and C29.

Old audio components usually begin to fail due to one or more key electrolytic capacitors failing. I find that most of the capacitors are still within their tolerances but there are always some on the edge of their limit or failed. That is the reason we go ahead and change them all out during these restorations.

On this Beogram the C24 2200uF capacitor had failed where it is way out of tolerance. It should have measured over 2000uF instead of just 475uF.

Quite a few others were also out of tolerance or on the edge of their limit.

The original C27 capacitor came with a three prong base to secure it to the PCB. This base is not found in modern replacement capacitors so I snap the original base off and re-use it with the new C27 capacitor. This makes for a good fit and I put a bead of hot glue around the base to secure the capacitor more than just the soldered on negative lead.

When I removed the original electrolytic capacitors and started to replace them I noticed that three of the black press-to-fit board connectors had deteriorated and were damaged (shown outlined in the next photo).

I always re-flow the solder on the board connectors anyway so after I finish recapping the board I will replace those damage connectors with some I have from a spare Beogram 8000 main board.

Here are the main board, microcomputer board and mod boards after recapping.

I will reflow the connector solder joints next and replace the damaged connectors. After that I will recap the motor capacitor in the transformer housing and the two capacitors that are mounted on the Beogram floating chassis. Once all of that is completed I will be able to test the Beogram electronic operation.