LC2 Repair

[lausvi]

Guy wrote:

I did had a quick search and found this: https://www.partco.fi/en/electronic-components/passives/resistors/flame-proof-resistors/12325-fres-05w-5r6.html … so I’ll either go for that or the TE Connectivity one that I linked to earlier.

Ha, Partco is my local (finnish) component dealer and this is the exact part I bought and where I got the part earlier 😀 I guess they do ship abroad too, but it might get costly…

(Again; I am not sure if this is 100% perfect part for this, but as the service manual doesn’t really give any details and the listing says flame-proof it sounded good to me and I used it for testing and was mostly astonished to find the LC2 working again with only this fix).

[Die_Bogener]

Caps make shorts and this depends on the voltage and temperature…

You have heard about “selfhealing caps” with polystyrene caps? Some elko caps do the same … and trick you out. It will happen again.

[Guy]

Update:

Resistor R1 5.6 Ohm replaced (temporarily with ‘metal foil’ replacement for controlled testing, now aware of fire risk).  Correct T1.6AH fuse also fitted (incorrect one was fitted by previous owner).

Tested LC2 again:

• 5V now present including to IR board.
• IR still not working.
• Touch control is working – dimming/switching correctly with 60W bulb fitted.

Obvious place to look next was the 2 x 22uF capacitors on the IR board.

I replaced these with 22uF 16v Tantulum beads that were left over from my BL5000 two-way repair.  Easier to solder than SMD replacements!

Now fully working with both IR and touch control ?

So a couple of questions before I place order with RS for correct fireproof resistor:

• Any reason that I shouldn’t leave those tantalum bead caps in place?  I am happy to replace them in the future if the IR stops working again.
• Any suggestions for replacing the (missing) little contact rubber between the PCB and the dome foil?  I was thinking of cutting a small piece from the Beo4 screen connection ‘rubber’.  Any better ideas, or is the part still avail from B&O?

Thanks for everyone’s helpful comments so far!

[Die_Bogener]

Tantalum ist very expensive, big and very longliving… 🙂

Tantalum hates spikes, overload and mechanical shocks. But this is here not the problem. Much better than this smd elko crap…

 

the rubber is done because of mechanical tolerances. The screen rubber will also work, but not so long… silicon screen rubber oxidates faster, but will also work for this.

It is also something like a fuse. Inside the case is a carbon paint for capacitive action. You should check it for cuts and breaks. It can be repaired with silver for windshields.

 

[Guy]

Thanks Die Bogener – all useful info!

However …

IR control worked for a while, then worked intermittently, then stopped working ?

Touch control is still fine, and 5v still being supplied to IR board.

Not sure what to look at next!

 

[Die_Bogener]

You have cleaned the acid of the smd caps?

[Guy]

Die_Bogener wrote:

You have cleaned the acid of the smd caps?

I actually cleaned the IR board before changing the caps, because the area (3-pins) where it connects to the main board looked discoloured. I have now given it a further clean and there is no change.

I have had to pack it all away now because 4-year-old grandson is staying this weekend, but I will have another play next week.

Thanks again for your suggestions.

[Guy]

So today I dug out the LC2 again.  Co-incidentally I had also found my Beoport (Beolink PC2) in order to investigate further for the Beoport thread.

With the Beoport I had packed what I think is a Beosystem 3 sensor (I don’t think I had used it with the Beoport because I used a VX sensor instead).

Anyway, just as an experiment I thought I would try replacing the LC2’s IR board with the Beosystem 3 sensor.  After a false start (where I got the IR and +5V wires reversed), I soldered it up and the IR control works very well.

Just for interest, here’s the inside of the Beosystem 3 sensor:

 

[Die_Bogener]

Maybe a good idea… replace this smd c(r)ap with something more reliable…

[Guy]

That new LC2 thread prompted me to dig mine out and have another go at fixing the IR sensor!  As previously mentioned I had been experimenting with a BS3 sensor – I even fitted a 3.5mm socket so that I could move it back to my Beoport for testing that!

Anyway, today I first replaced resistor R1 with a ‘fireproof’ metal oxide 5.6 ohm resistor – this one from RS: https://uk.rs-online.com/web/p/through-hole-resistors/1870824

I had to buy 20 so if anyone in UK needs a couple please PM me!

Anyway whilst looking at the IR PCB I checked the continuity of the IR signal and realised that the trace was broken hence the signal wasn’t getting to the main PCB – I must have damaged this inadvertently when I replaced the caps.  I re-soldered the IR PCB in place, soldered a quick wire bridge to R9 and now it all works as it should.

I am now going to experiment with finding something to replace that little contact piece that connects the touch sensor surface to the main PCB.

[johansoldradios]

Hey!

New to this forum, great to see so many B&O enthusiasts! I have a LC 2 light controller thats served me for several years but now it needs my attention. Initially it had an intermittent problem and didn’t turn on from time to time. Now it’s not responding at all. It got power in: 230 volt and out ca 226 volt unloaded and after load it drops to 10-16 volt. I would really appreciate if anyone have a schematic so I can study the design and not do the usual “guessing-game”. I’m suspecting the caps but before I just random recap the electrolytics, a schematic would be a gift from above 🙂

All the best

Johan

[Guy]

Hi Johan and welcome to Beoworld!

The service manual (including schematic) is available on site to Gold and Silver Members, so you’ll be able to download it if you upgrade your membership.

Good luck with the repair – I am sure that others will be able to offer advice also.

[johansoldradios]

Many thanks for the reply! I think I start with searching my own stash with old manuals and see what I find, otherwise It’s time to make some more measurements and see what I can find out that way. The other LC2 is still working and I can compare values with that unit, altho it need some more efforts.

[johansoldradios]

Update: The problem seems to be intermittent: now the LC2 is working, stabile 5V and both IR and touch is working properly. Took some ref. voltages to compare when it (probably) will stop working again.

Note: Some components seem to be changed before (the usual faulty capacitors and the PWM IC).

[Author]

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