Surface mount LEDs used to replace individual segment LEDs from the display.

The LEDs I used were rated 2.5-3.2 Volts @ 50 mA.

BM 8000 display module with lens filter removed.

BM 8000 volume display segment, half completed. The replacement surface mount LEDs are soldered on the left digit segement vs the original LED segment on the right digit.

The surface mount LEDs have a plastic lens over the semiconductor. Unless you are able to solder the LEDs in the exact position, the plastic molded cap which forms the digits will not fit over the surface mount LEDs. What I did was use an razor blade and shaved off the edges of each segment of the plastic mold to make room for the large LEDs. 

BM 8000 completed frequency display module.

BM 8000 Display Fully Restored.

A few things to note here. The top row of the display has been completely rebuilt.

The "Balance" segment did not have any bad segments and so I elected not to swap out the LEDs.

The true color of the original display is the ">" arrow segment of the Balance display.

The digit of the Balance display is much dimmer than it should be even though the LEDs are the original factory ones. The is because the digit segments are are strobed. This digit shares the same current dropping resistor as one of the digits on the top row. To make the replacement LEDs match the original intensity of the BM 8000 displays I had to change all the current dropping LEDs by a factor of 10X. I used 820 R resistors. Since the Balance digit is unmodified, the intesity there is now lower. I never use the Balance on the BM 8000 and so for practical purposes that display never comes on.

However this picture illustrates the relative intensities and color of the original vs new LEDs.

Excellent work! Very nicely done.

Hi Auric,

Agreed, well done!

I think you have solved an ongoing headache for many owners of these systems, who were not able to resolve the issue of the digital displays failing.... As an owner of a 6000 I'm feeling better now knowing that there is a solution that probably most techically savvy people can execute themselves and or get a repair centre to do for them...

Again, well done!

Laurence.

Derek,

Thanks for sharing the pictures and your painstaking repair process.  I am waiting for a few more parts then I will start my rebuild.  I probably have to do the same displays you did.  My volume and balance are completely dead.  The frequency has a few segments out.  I will post pictures of the completed process.

Gerhard

Superb work!

I'm very impressed with the results.

Chris.

Hi Gerhard:

Since it is unlikely that ALL segements would go bad on your volume display, I would suggest that you look at the decoder IC to make sure that it is not dead. Or simply measure the voltage across each segement to check for power.

Let me know how you make out!

Oh I also used a higher value resistor on the decimal segement of the volume display. Since this LED is on all the time (as power indicator). I didn't want to it to burn out prematurely so I made it slightly dimmer than the rest.

Derek

Hi Laurence:

Yes the problem with this solution is that it requires placing at least a pair of LEDs because of the strobing. 2 LEDs share one current dropping resistor. Also to match old LED with new requires selection of current value of current dropping LED so that the new segment will match closely with the old.

Thus for practical purposes it makes more sense to simply replace ALL LEDs at once. It's a lot of work and requires meticulous soldering since the surface mount components are so small.

So I'm not sure if this is really a "viable" solution for most owners. The repair shops would charge lots of money because is so labor intensive and time consuming.

One thing that I did not explore was to use off the self segment displays. It maybe be possible to custom make a PCB an simply reproduce the entire display module. This would be a easy and economic solution for everyone except for the "TP" display as a result. Fearing inconsistent results, I decided just to change the individual LEDs.

Derek

Really nice work Derek - that must have been a satisfying job well done :)

Laurence - just to point out that Derek is not the only one who has been rebuilding these displays. My BM 8000 had some work done on the LEDs on behalf of the previous owner a couple of years ago. I know of two individuals in Europe who have also been doing this for some time - that is in no way taking away from Derek's accomplishment - just to give others their due.

Well John... there are no Guiness book of world records here as far as I'm concerned, only sharing information that may help others keep these wonderful products around and functioning.

Member "Dillen" (Martin) has also come up with his proprietary technique (before I attempted my repair) to fix these displays. He reported success and was looking at offering kits, but I do not know if this has happened.

As always he is a wealth of solutions.

Derek

It's always a good thing when solutions can be found and what Derek shows here
is definitely a solution to a well-known problem.
There are kits readily available for display repairs. The kits have been made
very flexible to suit the individual owners' skills, both complete DIY-kits and readily rebuilt
displays on exchange basis (discrete displays or even whole boards) for all Beocords,
Beocenters and Beomasters using this family of displays - also the Beocord VU-meters.
My solution may seem a bit heavy, involving microscope, ionized hot air soldering,
solder paste and special tools for cleaning off the boards as well as
homemade holding and testing jigs whereas Derek's solution seems a
bit more "kitchentable-friendly" which is not bad at all.

I also like to mount the ultra-tiny 0402 rather than the 0603 LED's but soldering
even the larger 0603's (as Derek uses) requires a steady hand, I'm sure Derek will agree.

Great job !

Martin

Hi Derek,

Thanks for your reply and additional information... I think your report on doing this made it sound relatively easy for someone who knows their way around the electronics. But it does look rather time consuming and requiring lots of patience and steady hands... no coffee before hand.... 

So I'm wondering, what would you rate this in difficulty/complexity/labour intensity compared to a capacitor replacement? I recently had my system recapped with one of Martins kits by a local service centre, so I'm wondering for those of us who would need to go this route, would they be able to do this kind of repair?

I had wondered about off the shelf segments myself, but I guess sizes, specs etc may be difficult to match and source?

Hi John,

Yes , actually i did know Martin was offering rebuilds on the displays. I actually had one of the tuning arrows fail on my system which I thought was LED, but Martin came to the rescue and supplied the simple lamp replacement required!

I think that perhaps I misunderstood, as I thought that Martin only offered the rebuild himself, so it would involve sending the displays, in my case to him half way round the world. It would also involve me dismantling / installing the displays which i really don't think would be a good idea... ... What struck me about this is that someone handy can tackle the whole process themselves.

Anyhow, we'll face this bridge when (hopefully not too soon) we get to it!

Hi Martin,

I didn't realise that you had formalised the DIY kits for the displays... Sorry, obviously behind the times, i was thinking you were still doing all the rebuilds yourself as per my reply to John... So the kits are similar to the caps kits, any technician should be able to handle the rebuild? Thats also very good news!

So it appears this is no longer a headache, as we have a couple of good options to choose when resolving the failing LEDs.

Thanks

Laurence

Hi Laurence:

I think you have to be more "creative" than simple capacitor replacement; the task requires much greater skill and dexterity.

First you must disassemble the LED modules which requires desoldering multi pin devices! The B&O pcbs are not very high quality and so you must be very careful because you can damage the traces! Best to use a desoldering pump to suck up the solder. Too much heat will also damage the traces.

Once modules are removed, you must then dismantle the lens which involves cutting off the plastic pegs. Later on you use epoxy to glue the lens back on.

Once inside you need to remove the old LEDs and solder the new ones. If you don't have stable hands, the task will be nearly impossible as the parts are very very small.

I guess if you are good at soldering and desoldering it shouldn't be a problem. The trickiest part is really holding the smt LED stable while soldering one end. Once you have one end soldered the other is easy.

You should also buy plenty of spares. I ruined several LEDs before I finally go the hang of it!

I hope this helps.

Derek

Derek

Laurence,

I'm still doing most of the rebuilds here on displays and/or boards sent to me.
Handling, let alone soldering, 0402 LEDs (the whole component is only 0,5 x 1,0mm)
is not something "every technician" can do easily but there are some who can and
for them a DIY kit is fine. It also contains other components to convert the rest of the
machine for the rebuilt displays, these will have to be replaced regardless of
who rebuilds the displays, they are mainly resistors and are as easy as
the cap kits when the displays are done.
The displays will need to be dismounted from their boards.
It's very hard to do anything with tiny components on a sloping board.
Besides, in some machines some resistors that needs replacing are sitting right under
the displays so are not easily accessed otherwise.
But as Derek (and others) have just proved, I'm far from the only one who rebuilds
displays and geographically Derek is far closer to you than I.

Martin

Hi Derek and Martin,

Thanks for both your replies... obviously from what you both say, this job is not for everyone, I guess I'm just trying to understand from both of you the complexity, for both my own reference and of course the many beoworlders out there who may have units suffering from this...  to determine the options available...

Derek, just to let you know this is not a job for me... I couldn't even handle a simple speaker cap replacement! (with Martins very clear instructions no less) But thanks for your detail description, it will definitely prove useful for many more capable owners...

The reason I was asking you both if an average 'technician' could handle this is to determine if the kits could be ordered from Martin or the parts you list for instance and installed ... From what you both advise its most likely a bit of a gamble, so its probably best to get the displays removed and send them to Martin for rebuilding...... unless of course you want to start this part time... 

Thank you both and have a great weekend ahead!

Laurence

Well done Derek!
I am impressed with your patience.
Thanks for sharing this with us.

Andy T.

Derek, I take my hat off to you. Don't think I would even start to attempt a job like that.

Craig

I wanted to share my picture of one of the LED segments when it still works.  The total width of the LED and wire is 1.0mm.  The LED by itself is .5mm.  Modern LEDs have the LED and wire molded into a plastic housing which makes them much more reliable and durable.

Gerhard:

This is a beautiful picture. Your photography skills clearly exceed mine!

Perhaps you can take a picture of one of your faulty leds?

You are absolutley correct about the molded SMT Leds being more rugged. I don't think the LEDs actually "burn out." It's that wire that you show that becomes disconnected.

One less invasive solution (replacing all leds) that may work is to use silver solder paste (the type used in prototyping to draw conductive traces on PCBs or used to repair PCBs). Deposit a large amount of the paste on the pad and hopefully it will restore the connection.

Derek 

Derek,

Thanks for the compliments on the picture.  I love close up macro photoghraphy.  I have a closeup shot of a single dew drop on a spider web.  It's amazing!

I thought about your suggestion on the solder paste.  I'm just not sure what the wire is connected to on the LED.  I wasn't sure if there was some microscopic connection.  Maybe I'm thinking of it like a normal lightbulb, and the LED has connectivity all the way around?

Gerhard

Hi Gerhard:

Well one side of the LED sits on the pad. And the wire runs from the silicon waffer outside to the other pad. The silicon junction is encapsulated in red epoxy. I believe its where the wire connects to the other pad (ie out side world) that gets severed. So you need to put a pool of silver solder paste over that pad to bridge the gap.

If the wire is broken on the LED side then there's nothing you can do.

Derek

Derek

Your explanation makes sense.  I had broken wires at the LED side, not the pad side.  I removed all of the broken LEDs from the board, so I cannot provide a picture of the broken wires.  So, in my case the paste would not have worked as you explain.

Gerhard