Beocenter 7007 some LED indicators segments start to glow in stand by mode

Hello,

I have issue with Beocenter 7007 LED indicators, couple days ago i have noticed some LED segments most of time start to glow in stand by mode. I know that the same type of Beocenter has a aging problem with LED indicators, mine has too, some segment doesn't produce light, but now some indicators start to glow in stand by mode what before has newer been. Maybe someone are faced with a similar problem and managed it how to solve? I have electronics repair skills, However, before doing anything I want to ask, maybe someone has such defect repair experience.

Sounds like it needs a re-cap.

The segments in the displays are powered by tiny LEDs which will need replacing. I don't think you'll be able to find an exact match colour or intensity wise so you'll have to replace them all. It's an incredibly fiddly job so probably best to let someone who has done it before do it for you.

Hello,

I find time to check whats wrong with LED indicator on my Beocenter 7007. First problem was that the some LED indicator segment's doesn't work, this is common problem as I see with same type of Beocenter 7000 series due the aging.  After disassembly indicator board I find LED indicator segments failure cause, a LED crystal tiny anode wire which are tear of from the contact pad. I have solder back wire to contact pad and LED segment start to work. Also I have noticed that the most of wires are tear off from the welding point on the contact pad, and contacting only by touch, and any time can stop to work. So I have perform soldering work to all of LED segments anode wires. You can see cause and result on the attached photo. Alternative to soldering I think it can be conductive glue. So first problem are solved.

But still, I have issue with glowing LED indicators in stand by mode, which in my opinion is not normal. Maybe this is can be segments decoder IC or display drive IC issue, or some capacitors need's to be replaced. Maybe some one have normal service manual for Beocenter 7007 ?  

Also I have noticed that the some bakelite ROE caps 100/40 EK on the power amp board have little convex housing top maybe they are still good but look suspiciously. 

Sorry for poor grammar, English is not my main language

I have also tried to solder the thin wires in the displays but never found it a good solution.
The problem is that the solder pad is copper and the thin wire seems to be stainless steel and it's not easily soldered together.
Even if it looks fine, the solder hasn't properly bitten into the stainless steel and the contact will fail intermittently.
Maybe you have more luck.
They are spot-welded from factory.

The standby problem could point to a problem in the power supply. Either unstability from aging filter capacitors or one or more voltages
are simply not shut down correctly when in standby.

Martin

Thank you Martin for your comment.

Yea that wires are nasty to soldering but after all soldering work I have checked wires contact touching them with a needle and seems like they have good connection I hope it will last for a long time. In worst case I have plan B, if they stop to work, replace LED crystals with same red color SMD LED, or maybe some experiment with different colors LED. But I like to keep all thing unchanged 

Now about the power supply electrolytic capacitors, most of them are Roederstein manufacture

ROE Bakelite Polarized EKU series:

 

• 22uF 40v (c1)                  x1 additional marking on capacitors - T2

 

ROE Bakelite Bipolar EKU series:

 

• 47uF 6v (c112,c212)       x2 additional marking on capacitors - TN
• 47uF 40v (c15)                x1 additional marking on capacitors - TN
• 100uF 10v  (c105,c205)  x2 additional marking on capacitors - T8

 

ROE Bakelite Polarized EK series:

 

• 100uF 40v (c100,c200)  x2 additional marking on capacitors - TN

 

WICON 3 large capacitors aluminum cans next to each other:

 

• 4700uF 35v (c17, c18)  x2 additional marking on capacitors - type KP44735x1
• 4700uf 25V  (c4)           x1 additional marking on capacitors - type KP44725x1

 

And some others Elna, ROE,... typically look electrolitic capacitors

Actually I worried about the availability to get same manufacture vintage caps, because I found only a few identical on ebay and dat's it, such other i don't know where to get. I want to keep the more original characteristics but if I can not find same I will have to use alternatives... There fore, I want to ask your advice what capacitors brend/type could replace original with good overall result.  Maybe some one have already done capacitor replacement and can share experience, especially after replacing ROE bakelite capacitors with alternative one

And one more thing I actually doesn't know what is mean marking on ROE caps like EK, EKU and additional  TN T2, T5, T8, T7 which I have found on ROE caps. Maybe some one can explain

Sergey

 

The letters etc. are type indicators and probably date of manufacture but I would definitely not
fit new old stock capacitors and I would certainly steer clear of unused old stock red Roederstein caps even
if they pop up on Ebay and elsewhere listed as "audiophile" and the one and only miracle cap for your guitar amplifier.
They were good quality components when new, but that was 30+ years ago.

Anyway, I suggest you locate and repair the present fault before "upgrading". There's always a risk of introducing
new faults that could be very difficult to diagnose if the unit was already at fault, before you began.

Martin

Hi, 

Martin, you are right.

After inspection of most electrolytic capacitors in power supply, indicators and control board most of capacitor have even greater capacity than specified, having in mind that the most of capacitors can have ±20% tolerance seems like they are normal. I doesn't find any clearly noticeable  bad or unusually heating components.

So after not find noticeable problems, I assemble everything back. despite the LED indicator segments still glow in stand by mode and operating mode. I thought that this does not prevent for me. But after night in stand by mode i notice that the LED segment's with whom I have a problem glow more intensive than the before.Actually LED segment start to glow more intensive with the time when device are connected to electricity. After turn on device by pressing the desired program button, for example P6, turns on the random program P1 or any other... and after selecting another, reacts as if I clicking on "Mute" button, also indication appear, I try to turn off device by pressing "dot" marked button, device start another function like tape player  and metal tape indicator appear only after second attempt device turns in stand by mode. Seems like it has become not only indicators problem, I think that this is related with the processor normal operation disorder, I decide continue inspection and repair. I want to find problem cause and fix my B&O

Maybe some one have better service manual and schematic? than just schematic can be found at web. Would anyone have any useful suggestion where to start or continue repair?   

Regards, 

Sergey 

Increased capacitance is a typical sign of a bad capacitor.

Think of the capacitor as an elastic band;
- When good, it will stretch within a certain range and it will return to original length when released.
- With age it will gradually become easier to pull and less elastic and will no longer go back to original length - it will always end up longer.
- At some point, it will become very long and never go back again.

Martin

Finally I find what exactly causes the problem 

I have tried to change LED driver IC's and BCD to decimal decoder's, without the results, problem still remaining. Power supply voltages are ok, microcomputer self test pass, show 0P that mean microcomputer is OK. Situation was weird...

Until I find one LED first digit "d" segment have little reverse current leakage. I find it using my new multimeter, previous used multimeter seems like was not enought sensitive and didnt show problem with LED's, at all, that was made difficulty to find problem. Such a small barely finded defect cause LED glow in standby mode and buttons missclick.

Problem solved. Now everything work fine as it should