Beomaster 8000: Display Board (part 2)

I completed installing the new SMD LEDs in the remaining three Beomaster 8000 display modules. It was pretty much the same as with the first display module except a lot more LEDs to solder. The job is quite tiring on the eyes.

If you are looking at refurbishing your own display modules I can tell you that the best method I have found is to solder one side of the SMD LED first, then check the fit of the display light guide. Last year I tried using an SMD work station that has a hot air gun and a board heater along with SMD solder paste. Unfortunately the solder pads on these display board are too wide and the hot air gun would blow the SMD LEDs out of alignment (but still on the solder pad).

The result was a lot of rework by hand so it is better to just do the LED soldering manually to begin with. One side first, a fit check and finally the other side. Tedious for sure but the displays work the first time this way.

I started with the largest display module, the FM channel display and worked my way down to the volume level display. Here is the FM channel display  beginning its testing.

Here are all four displays powered up on the test jig.

I will let them burn-in for twenty-four hours before I seal up the modules for re-installation on the Beomaster display board.

Once the displays are back on the display board it will be time to reassemble all of the refurbished boards in the Beomaster 8000 chassis and try this restored receiver out.

Beomaster 8000: Updating the Displays - Completed

Today I finished replacing a set of Beomaster 8000 display LEDs with SMD LEDs. This set had numerous faulty display segments so it was badly in need of repair.

I was a little disappointed that my SMD work station method of doing this task fell short of expectations. In my earlier restoration of the Beocord 9000 displays the work station method worked quite well and I felt like I only needed to perfect the process a little before it became my new way of doing these displays. Now I think that was just beginner's luck. Since that first display repair the SMD work station technique has meant a lot more rework and waste of new SMD LEDs (that had to be tossed when the installation failed).

The problem with the SMD work station is that even with minimal air flow, the SMD LEDs can shift during soldering. Even in the case where the solder pads are small I usually run into over half the LEDs not soldering in the position they need to be. With these Beosystem LED displays it is critical that the LEDs stay within a narrow range in their positioning. The reason for that is they have to fit nicely in the slots of the plastic housing that guides the light.

So after that hopeful experiment I have reverted to the tried and true manual soldering process.

To show what I am talking about here is the preparation for the Beomaster 8000 channel balance display. This picture shows the SMD LEDs in place on their solder paste ready for the heat to be applied.

After the board heater and heat gun melted the solder, the result was quite unsatisfactory.

The LEDs circled in red were not successful. I had to toss those LEDs as I don't trust them to be reused once I remove them. These SMD LED devices are pretty delicate so I don't want to risk them failing later on.

Here is the reworked board after manually repairing it with old fashioned tweezers and soldering iron. I used my de-soldering gun to clean up the excess solder.

Now that I decided to change over to the manual soldering method I prepared the next board by cleaning with alcohol and tinning the solder pads. This is the Beomaster 8000 volume level display.

Before placing the SMD LEDs I apply some solder flux with a syringe. The SMD board heater at least provides a nice way to hold the board in place while I work on it.

Here is the completed volume level display. As I did each display I was able to refer back to my photos I posted in the previous post that show the LED orientation on the pads. That was very helpful as I could just look at my smart phone for the reference photo as I placed and soldered these LEDs in place.

Next is the Beomaster 8000 function display. Here is the prepped board.

...and the finished board.

Finally the last board, the FM frequency display board. These display restorations are probably the most difficult job of the entire restoration. The work is very trying on one's patience as it is easy to get frustrated if you can't keep a steady hand. You have to be in the right frame of mind when doing this. 

Here is the last board before tinning. The marks between the pads is where I used a razor knife to cut the tiny pad the original LED mounted to. I found that trying to leave in place is risky because it is such a narrow gap. It is easy for solder to bridge that gap and cutting it out leaves a perfect gap for these SMD LED components.

Here is the board tinned and with solder flux in place on the pads.

The last board is now complete. One other note about the manual soldering process. I often just solder one side of the SMD LED to hold it, then test fit the light guide piece to make sure the LED component is centered in the slot. That is an extra step but it actually saves rework time and risk in destroying a good SMD LED. After I verified the fit I solder the other side of the LED.

Now it is time for the display burn-in test. I reworked my test jig since the last post and I am now going to leave these displays operating for 24 hours to make sure none of them are faulty.

Just for a reference I put the channel balance display completely back together (just pressed together, not permanent yet), the volume display and function display with just the light guide attached, and the FM frequency display bare. You can see the progression that the parts play in the final look of the display.

While these display modules are testing I can start work on the Beomaster display board recapping and the Microcomputer board recapping.

Beomaster 8000: Updating the Displays - Preparation

The next task on the list is updating the Beomaster 8000 displays. For the big, segment displays that means replacing the original Beomaster LEDs with modern, surface mount type LEDs. It would be great to be able to leave the original LEDs  (and sometimes an owner will do that), but eventually those LEDs fail. These units are thirty-five years old now. It is expensive to ship a Beomaster 8000 due to its size and weight plus it is a good idea to keep shipments (as in re-shipment) to a minimum. Lessen the chance of something bad happening in transit.

Here are the segment displays from some Beomaster 8000 units.

The first step is to get a test rig set up for these Beomaster displays. The work will be just like I did earlier on the Beocord 9000 display (...just more LEDs). You can setup a jig without load resistors and use the current limiting of the bench power supply but I want to set up my jig with individual control lines and load resistors like the Beomaster. I came close on this initial test set up but ran short of 68Ω and 82Ω resistors. I will have to add them to my next Mouser order which will probably be this week. Anyway, though not completely like I wanted, this test rig will allow me to check the reworked display boards. This picture shows the rig with a set of Beomaster 8000 displays that have all working LEDs.

Here are the individual Beomaster 8000 display pin mappings.

Now I am off replacing the LEDs with new SMD LEDs. Once that is complete I will use the test jig to run the displays for a few hours so I will know they are good. Then they will be assembled and re-installed in the display board. While the LED burn-in test is running I will be able to do the recapping of the display board and the microcomputer board.

Beomaster 8000 Display Repair Marathon

****note: This post is 'historic'...Please, visit this page for my latest display repair procedure: http://beolover.blogspot.com/2012/09/beomaster-8000-display-repair-hopefully.html****


I am on a roll!!! Today, I did the displays of my second Beomaster 8000 in one setting. Desoldering all the displays at once, opening them up, putting the SMD LEDs in...it took a few hours, but they look very nice. My best result so far...I guess practice pays off...;-).

I made one further change to the procedure: I used "No Clean Flux Paste" from MG Chemicals. I realized that paste does not evaporate as quickly as the liquid flux does. This makes it possible to put flux on all locations at once and then put the SMD LEDs on in one setting. It is recommended to do them in sequence by orientation, i.e. do all vertical ones in one setting, then the horizontal ones. This speeds the process up considerably. Also reliability increases. This time I had no failed LEDs. They all withstood the toothpick stress test (yes, not only European banks get this test...;-). The "No Clean" aspect of the paste did not work. I probably put too much on there. Therefore, I washed the boards in ethanol with a toothbrush. This worked very nicely. Here some pics of the completed boards:

I like doing the balance display best now. I realized that the smaller pads in combination with the green solder mask stops the solder from spreading.  This makes it much more straight forward to get enough solder on the contact pads of the LEDs. It also prevents the solder from obstructing the bezel, which fits perfectly after the refurb without the need for Dremeling the slits to allow for the solder thickness...These pics show the balance display board: