ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I have been focused on Beomaster 8000 and 6000 receivers lately. That means eventually having to deal with some units that have displays with broken segments. The Beoworld Archived Forum has some good information from some members regarding repairing these displays using SMD LED components. This weekend I decided to try my hand at it.
Here is the original TP8 display from a Beomaster 6000. You can see how tiny (and likely impossible to repair) the original LEDs are. The red "A" on the boards mark the anode traces.
Here is another picture of the original display with one of the working LEDs illuminated.
Using information from the archived Beoworld thread, I ordered a sampling of SMD LEDs for my experiment in looking for a good replacement.
1. ROHM SML-P11VTT86 - SMD Low current Picoled RED, 20ma, 1.8V, 0402 PKG, 626nm Color Temp, Transparent, 3.6 mcd intensity.
2. Lumex SML-LX0603IW-TR SMD Hi-Int Red, 20ma, 2v, 0603 PKG, 635nm Color Temp, Milky White Diffused, 14 mcd intensity.
3. Vishay VLMS1500-GS08 Super Red, 30ma, 2v, 0402 PKG, 631nm Color Temp, Water Clear, 54 mcd intensity.
4. Vishay VLMS1300-GS08 Super Red, 20ma, 2v, 0603 PKG, 631nm Color Temp, Water Clear, 54 mcd intensity.
I have several of the TP8 display boards that need reworking so I chose one with a lot of burned out segments to try several of these SMD LED components on. Here is the first test. It was my first time using an SMD rework station and I don't have the technique really mastered yet. However, I got all of the display segments changed and was able to test the result. I applied 6.5 VDC to the anode lines and ran the cathode side through a variable resistor set to around 570 ohms.
All of the segments illuminated. You can see that the LED set marked "2" is dimmer than the others. It looked like the best candidate to me.
Here is the test board with the cover back on.
Now I took one of the TP8 displays I wanted to try a real test with in a Beomaster 6000. I selected the number 2 set of LEDs - Lumex SML-LX0603IW-TR, 0603 PKG, 20ma, 2V, 14mcd, milky white diffused.
Here is my second round of doing SMD work attaching the LEDs to the board.
This is the board after applying heat.
Here is the result. It looks fairly decent by itself.
In the Beomaster 6000 however, it isn't a perfect match with the FM frequency display. The new display is a little brighter and the shade of red isn't exactly the same. One option of course would be to replace the FM display so they would match. I don't really want to do that to a working display though. I will have to keep searching for a better substitute and/or (maybe) playing with a lens insert to adjust the color and brightness of the reworked display.
Excellent thread and work!
//Bo.A long list...
Great results and wonderful pictures, as always!
But with some many people spending so much time with this same problem, I can't help but thinking that it might be feasible to have a batch of new display modules made industrially with modern components. Reuse the old plastic frame, and the display PCB is about the simplest thing you could manufacture (when an assembly machine does it). Would probably need a three-digit unit count, though, and I have no idea how many of these would actually be needed, even globally.
--mika
Brave man John!
I too have a defective TP display on my 6000 - it lacks the central segment on the P.
But fixing it is something I have not been able to tackle yet. Rudy here also does a wonderful job, and so does Martin of course I reckon!
Jacques
Nice job!
Maybe a piece of transparant white paper to diffuse the light from the brighter versions?
Soldering the 0603 was easier than the 0402 version I guess?
Thanks
Using soldering paste and a hot air pen from an SMD workstation makes the soldering part of a 0402 and 0603 about the same. However, picking up and placing the part is way easier with the 0603. With the 0603 though, I found it easier to work if I cut the small pad where the original LED was mounted (between the two large pads). I'll post a picture of what I mean by that later.
Yes, I am going to try some material to further diffuse the light. That's a good idea.
I did ask Martin a question about the lighting and he brought up that the old LEDs have often faded over the years. That means finding a match will vary. The only sure way of matching will be replacing all of the LEDs. There are a few other SMD LEDs that I want to try so I think I will order some this week.
Today I picked up some red color plastic. It is by Dura-lar and is the same material I use for shims when I refoam speakers. I have also used it as the slide guide on a Beogram 8002 lid repair. The material comes in various thicknesses (all extremely thin). It is very durable and does not tear or yellow. I cut four pieces to use as additional filters in the BM6000 TP8 display. Using all four with the white diffuser piece (original in the display), the result looks pretty good. I inserted the four Dura-lar, red pieces into the red display cover first. Then I placed the white diffuser piece in the cover last. So the LED light hits the diffuser first, then goes through the layers of red plastic.
Here is the result. I think it looks pretty good.
John, could you tell me more about the way to solder SMC LEDs?
There are numerous tutorials on the web, but they are not very satisfying, and none uses solder paste.
I would like to practice on my second Beomaster, whose display misses quite a few segments - about half of them actually!
Did you finally use the Lumex?
Yes Jacques, I used the Lumex SMD LEDs on that BM6000 project. Since then I purchased a board heater to heat the underside of the LED PCB before applying the heat nozzle to the solder paste on the component side. I haven't had a chance to use it yet but I can set it up to take some pictures to show you. I also intend to build some connector jigs for the various displays from that B&O series of components so I can test the displays easier (before and after). The breadboard setup was okay on that first repair but I would rather have something dedicated that can quickly test the displays. My own BM6000 that I recently repaired has a couple of segments out in the FM display board so I do have a need to get back to some display repairs. The problem is I have a Beogram 4002 (type 5503 - AC motor) disassembled on my workbench right now. In a couple of weeks I get two weeks off between Christmas and New Years so I hope to get a few things done. I'll try to send you some information on the soldering tomorrow.
Thanks John. Looking forward to that.
Here you go Jacques...On the BM6000 display repairs I made earlier in this thread I got away with using just an SMD heat gun and the solder paste. The results were good but I was informed that it is much better to pre-heat the board before hitting it with the heat gun. So I aquired this Aoyue 853A pre-heater. It has adjustable mounting brackets to hold the board and it has a temperature probe to check the actual pre-heat temperature. The picture shows what it looks like with the BM6000 function display board mounted. The purpose is to have the pcb heated to a value of around (150 F/65.5 C) before using the heat gun on the paste (on the component side). This reduces the amount of time the higher heat is placed on the component because the board is already warmed up.
Here is a closer picture of the mounted BM6000 function display board.
Before I rework another display I am going to build a test jig for the display boards so I can quickly check them (before and after). That project will have to wait until I can clear my bench of my current projects though.
Thanks John.
Would it be a good idea to superglue the SMC LEDs before soldering them? Knowing that acetone could always be used in case of failure...
Is THIS the technique that you use?
chartz: Thanks John. Would it be a good idea to superglue the SMC LEDs before soldering them? Knowing that acetone could always be used in case of failure... Is THIS the technique that you use?
That air gun is too big. You should use one like this. That is how I did my first displays. Doing it that way, the paste is sufficient to hold the component in place and the air gun shouldn't move. I have gone a step further now and added the board heater so I shouldn't need near as much heat from the SMD workstation heat gun now.
chartz: Would it be a good idea to superglue the SMC LEDs before soldering them? Knowing that acetone could always be used in case of failure...
I use this SMD rework station. It works pretty decent. The vacuum pickup tool isn't very useful for small things like the LED SMD components. It is better to use tweezers. I haven't used the soldering iron much as I already had a nice Hakko that I like to use.
For picking up the SMD LED components I use tweezers like these.
Thanks, that is very useful John.
@ Sonavor.
Would you still suggest to use the Lumex with 14MCD? Or would you advise a less brighter version for replacing the leds?
I'm afraid I haven't been back on these displays in quite a while. I intend on making jigs for the various B&O displays and do some more testing. I would like to see if there are some better options now but I've been tied up on Beogram projects lately. To answer your question though...If you are doing a complete replacement of all the LED display segments, then the 14MCD should work well. If you are just repairing one section and need to match an original section, then the 14MCD will be a little brighter. I was able to match up the brightness levels on a Beomaster 6000 repair with the Dura-lar (red tinted material). Rudy (Beolover) has been successfully repairing his Beomaster 8000 displays using the same SMD LED (Lumex SML-LX0603IW-TR ), then fine tuning the brightness with resistors. You can read his repair here.
Thanks!
Ordered several leds and will see where it ends.