Beomaster 5500 sound slowly degenerates over 10 seconds

33 replies
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TheDane (archived2)
Bronze
24 posts
Posted January 24, 2020 at 12:35 GMT
#2132315

Hello out all you fellow B&O enthusiasts :)

Thank you for this amazing board, and all there is to learn here😁

I post this, because I have this problem with my newly bought beomaster 5500.

Everything works flawlessly and the sound is absolutely amazing with my beovox 4702! But recently at has begun to degenerate the sound over a matter of 5-10 seconds, until an almost complete silence at the end. The degeneration at first sounds like a bit of distortion, then it gets worse and worse until it only sounds like a lazy dog farting (sorry for my language use here😎)

I can keep the degeneration away by adjusting the volume up and down 1 step at a time, adjusting balance, adjusting bass or treble setting. but the same moment I lay the remote to rest, the sound starts to degenerate.
The exact same failure occur in the head-phones when plugged, and with the exact same sound-degeneration.

What I have done so far:

- Checked the cooling ribs, and they are fine. Not heated.

- I measured resistors in the amp-section, and they are within specs.

- I changed the 22nF and two 10nF caps placed at the power-supply to new ones.

- I have unmounted the accessplate under the beomaster and visually inspected everery soldering

None of this gave any results nor hints of what to do!

Could it be the mute-relay/phone-relay?

No-one has ever described this kind of failure in a beomaster, so I am in a bit of a confused state right now...

Please, any advice is welcome 😐

Best regard, TheDane

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TheDane (archived2)
Bronze
24 posts
Posted February 9, 2020 at 20:09 GMT
#2132316

Hi again,

Any ideas, guys?

T(
TheDane (archived2)
Bronze
24 posts
Posted February 11, 2020 at 19:09 GMT
#2132317

Thank you for reply. Forgot to say, that the mute-relay works like a charm. Everything works, output 1 and 2 and also the headphones output. All input works aswll and also the radio and so on.

Only Thing is, that All output (speaker 1 and 2 and headphone) play sound which start out perfekt only to distort more and more, until it after appr. 10sec. sound like a farting dog, regardless which input/output I choose.

My Best guess is some caps om the preamp board, since I changed caps around the mainpower.

Any ideas?

T(
TheDane (archived2)
Bronze
24 posts
Posted February 11, 2020 at 22:17 GMT
#2132318

Thanks solderon

C9 and C10 I have replaced as My first effort. I Will try following your instructions and reply when I'm done.

T(
TheDane (archived2)
Bronze
24 posts
Posted February 14, 2020 at 17:19 GMT
#2132319

OK, Im back. I have cooled All ICs on the board to appr. - 30 degrees celcius, and the problem persists. I have noticed, that the backup battery may need to be replaced, because it cant memorise when unplugged from 240V. Can this be the problem? It would be Nice if you know, because otherwise I will need to re-cap the entire preamp soon, to be able to seek-n-destroy the fault.

SO
solderon29
Gold
1051 posts
Posted February 14, 2020 at 17:33 GMT
#2132320

Did the voltage checks around IC4 and 5 reveal anything?

Nick

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TheDane (archived2)
Bronze
24 posts
Posted February 14, 2020 at 23:00 GMT
#2132321

Hi again

So I made a "diode-test" on every pin on each IC on the preamp. IC 1, 2, 3, 4 and 5 are in perfectly good and operational condition. But-but-but, IC nr. 6 (the TC9184p from Toshiba) was in poor condition indeed. L/R bass-control aswell as L/R treble-control aswell as some other pins seemed to be shorted, when connected to the GND-pin.

I think the TC9184p IC is burned, and this could explain the particular habit of the reciever, that when it plays parts of music, where there might be extra bass or treble, then the sound starts to deteriorate/degenerate even faster. Maybe...

I still cant figure out, why it plays so well the first 2-4 seconds (some times longer), when/if the IC is faulty (even when cooled down to minus 30 degress celcius).

Ok, I think that I will wait re-capping the preamp for now, because if the failure is the TC9184p IC, then I will not obtain better sound quality from my beomaster, before I have replaced the faulty IC either way.

Maybe I can find my sparepart in China somewhere, so it may take awhile before I can write you the result.

TheDane

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TheDane (archived2)
Bronze
24 posts
Posted February 15, 2020 at 15:26 GMT
#2132322

Yes, Im not happy either to buy in China, but it seemed like the only way. All my searches led to China... until you wrote😊 can we PM on this board?

T(
TheDane (archived2)
Bronze
24 posts
Posted February 15, 2020 at 22:35 GMT
#2132323

Re-capped the entire pre-amp board anyways. The problem is still there, but I already had a clue that the caps werent the problem, so HEY, COULD ANYBODY SEND ME A NEW TC9184P IC? 😐 if you please🤩😋

Sincerely your truly fan forever if you provide me with a Tc9184p IC

The Dane

DI
Dillen
BronzeModeratorFounder
12777 posts
Posted February 16, 2020 at 08:06 GMT
#2132324

TheDane wrote:

Re-capped the entire pre-amp board anyways. The problem is still there, but I already had a clue that the caps werent the problem, so HEY, COULD ANYBODY SEND ME A NEW TC9184P IC? 😐 if you please🤩😋

Sincerely your truly fan forever if you provide me with a Tc9184p IC

The Dane

You have email.

Martin

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