[KolfMAKER]

Great to hear you have practical helping hands to support you. Good for you!

For the interest of others reading this topic, please come back when your issue has been resolved. And ask your friend to write a short summary of the cause and how he solved it.

 

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

Thank you, the photos help understanding.

A few things are still unclear to me:

1. During your test with the Pioneer headphone output, approximately where was the volume control set?
   Very low, medium, or normal listening level?
2. For your tests, did you put the  small switch on the bottom of the BeoLab 8000, to the lower position (LINE – see picture) when using the RCA input: yes/no? (The speaker may not work correctly from the RCA input when the switch is in the PowerLink position)
3. Can you connect the working BeoLab 8000 using exactly the same setup:
   • same Pioneer amplifier
   • same cable
   • switch in the lower (LINE) position
   • same volume setting
   • Can you share the results of this check?
4. Also, when the faulty speaker LED is green, do you hear absolutely nothing at all?
   No hiss from the tweeter, no hum, no clicks from the drivers?

This information will help narrow the fault down considerably.

 

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

Hi Christian,

One important question that may help us narrow this down: How exactly are you testing the speaker?

Are you using:

• PowerLink from a B&O source?
• The RCA input?
• Something else?

You mentioned that the LED turns green when you power the speaker on. Does it also stay green while music is actually playing?

Knowing how the speaker is being driven is important, because it helps us determine whether the amplifier is receiving an audio signal at all, or whether we should focus on the audio input stage first.

The fact that the LED goes green and the relay clicks is still encouraging, as it suggests that a large part of the electronics is functioning normally.

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

Thanks Christian, for posting the photos.

I don’t immediately see any obviously burnt components, damaged tracks or leaking capacitors, which is hopeful. Before measuring anything complicated, can you tell us exactly what the speaker does? (When connected via PowerLink/Line-IN and starting music):

• Does the LED stay red permanently?
• Does it change from red to green when a signal is present?
• Do you hear any clicks from inside the speaker, when music is started?
• Does the other speaker still work normally?

Let us know your findings.

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

Hi Christian,

The fact that the red LED still comes on is actually encouraging. If the main fuse had completely blown, I would normally expect the speaker to be completely dead.

Since the speaker was accidentally connected to 220V while still configured for 110V, I suspect the standby power supply may still be working, but another part of the power supply could have been damaged.

My suggestion would be to start with the basics:

• Check the mains fuse with a multimeter (power disconnected).
• Post clear photos of both sides of the power supply board.
• If you are comfortable using a multimeter, measure the secondary supply voltages coming from the power supply.

Also, did you hear a pop, smell anything burning, or see any smoke when it happened? And does the other speaker still work normally?

Those details may help narrow down the fault considerably.

Good luck, and don’t give up on them yet — the fact that the LED still lights up is a positive sign.

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

I would not worry too much about the 4-layer PCB at this stage.

Yes, an internal track or via failure is possible on a multilayer board, but based on the symptoms I do not think it is the most likely explanation yet.

The reason is that you already have several strong clues pointing towards a localized thermal issue:

• cooling around C401/C403 restores the sound,
• replacing C401/C403 did not solve the problem,
• TR405 starts oscillating when the fault occurs,
• the behaviour is repeatable and temperature-dependent.

To me, that still sounds more like a component, solder joint, via, regulator, transistor or local control circuit problem than a hidden internal PCB track.

I would wait for the proper freeze spray and continue narrowing down the exact area by cooling individual components one at a time.

In particular, I would focus on:

• TR405,
• components directly connected to TR405,
• nearby capacitors, resistors and diodes,
• and any ICs or regulators in the same section of PCB32.

Only if the freeze spray testing fails to identify a specific component or area would I start considering an internal PCB defect as a more likely possibility.

At this point I still think there is a reasonable chance that the actual fault can be isolated and repaired.

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

Hi Edo, thanks for your update.

I actually think this is progress. The fact that replacing the TDA1305T did not change the behaviour strongly suggests that the DAC itself was not the root cause. What I find more interesting is that:

• cooling around C401/C403 restores the sound,
• replacing C401/C403 did not solve the problem,
• and TR405 starts oscillating when the audio disappears.

That makes me wonder whether C401/C403 are simply close to the actual faulty component, rather than being the fault themselves.

At this point I would focus on TR405 and the components directly around it. It may be useful to measure the base, collector and emitter voltages of TR405 before and after the fault occurs.

Once the freeze spray arrives, I would also try cooling TR405 and the surrounding components individually rather than cooling a larger area of the PCB. To me, TR405 and its local circuitry now look like stronger suspects than the DAC.

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

Hi edo,

That is actually very useful news! If cooling down PCB32 brings the sound back, then the problem now looks clearly thermal and the TDA1305T itself is much less likely to be the root cause.

My first suspects would be:

• voltage regulator(s) on PCB32,
• electrolytic capacitors around the DAC / audio supply section,
• local decoupling capacitors,
• mute / output stage transistors,
• bad solder joints or hairline cracks,
• possibly a clock/buffer component around the DAC section.

 

Suggested steps:

I would not cool the whole board anymore, but use freeze spray very locally, component by component.

Start with the power regulators and capacitors around the DAC/audio section, then the muting/output stage components, and finally any logic/clock components feeding the DAC.

Also, it may be worth checking the DAC supply rails again with an oscilloscope, not only DC voltage. A regulator or capacitor can still show 5V DC while having noise/ripple or instability when warm.

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

Good luck!

🤞🏻

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

That sounds like a reasonable approach.

As far as I know, there are no known Beosound 9000-specific versions of the TDA1305T. The TDA1305T is a standard Philips DAC, used in many different audio products of that era.

Therefore, if:

• the donor DAC board is working correctly,
• the donor TDA1305T is healthy,
• the IC is removed without damage,
• and it is soldered correctly onto the BS9000 board,

then I would expect it to work in the Beosound 9000 as well.

What makes your case particularly interesting is that the replacement will also act as a diagnostic test.

If the donor TDA1305T works normally and the fault disappears, that would strongly confirm the original DAC was defective.

If the donor TDA1305T shows exactly the same behaviour as the original IC, then I would start to suspect that something else around the DAC stage may still be contributing to the problem.

In any case, using a known-working donor IC from a complete DAC board gives a much higher level of confidence than buying loose ICs from unknown marketplace sources.

Please keep us updated on the result after replacing the TDA1305T with the donor board one.

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

I think purchasing the complete DAC board was probably the best decision at this point.

After all the measurements, the diagnosis now seems much clearer:

– digital data signals remain present,
– clocks remain present,
– supply voltages remain stable,
– mute line does not change,
– CD mechanism continues operating correctly,
– but the analog signal disappears directly at the DAC outputs.

That combination now strongly points to an internal DAC failure.

Also, the fact that one replacement IC worked briefly before failing could indeed suggest reclaimed, marginal or counterfeit parts.

Using a complete donor DAC board is a much safer approach because it also eliminates possible uncertainties regarding soldering, surrounding components and PCB-related issues.

Please keep us updated — this has become a very interesting diagnostic case.

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

Thank you, that is a very important additional test.

If I understand correctly:

– BCK remains OK
– WS remains OK
– DATA remains OK
– VDDA / VDDD / VDDO remain stable at 5V
– MSUB remains at 5V
– and the analog audio signal disappears directly at the output pins of the TDA1305T

Then I agree: this makes the TDA1305T itself the most likely cause.

At this point the problem is probably not the CD mechanism, not the digital signal going into the DAC, not the supply voltage and not the mute line.

The difficult part is finding a trustworthy replacement. Since the TDA1305T is an old Philips/NXP DAC, I would be very careful with Ebay or AliExpress parts. They may be reclaimed, relabelled or fake, even if they look correct.

I would try:
– NXP authorized distributor network
– Rochester Electronics
– professional obsolete component suppliers with traceability
– or possibly a donor board from another known-working unit

Personally, I would avoid buying more “new and original” ICs from unknown marketplace sellers unless they can provide proper traceability.

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

Thank you, that is useful information.

If BCK, WS and DATA remain OK, and VDDA / VDDD / VDDO all remain stable at 5V before and after the audio disappears, then the digital input signals and supply voltages to the TDA1305T seem to be present.

That does make the DAC a stronger suspect than before.

However, I think there is still one very important measurement missing:

Is the analog audio signal still present directly at the output pins of the TDA1305T after the sound disappears?

If the analog output from the DAC disappears while BCK / WS / DATA and all 5V supplies remain OK, then I would agree that the DAC itself becomes very likely.

But if the analog signal is still present at the DAC output pins, then the problem must be after the DAC, for example in the muting circuit, output stage or coupling components.

So in my opinion the next decisive test is to check the analog output directly on the DAC pins before and after the fault occurs.

Let me know the outcome!

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

Thank you, this clarification is useful. What I now think is:

The fact that the original IC always returns to exactly the original behaviour probably means:
– the board itself was not permanently damaged during the IC replacements,
– the original fault is still present in the same signal chain,
– and the Ebay IC’s may indeed be questionable, but they still do not automatically prove that the original DAC IC is the root cause.

The 3 different behaviours with the 3 IC’s are interesting:
– original IC → sound disappears after 1-2 minutes,
– replacement IC #1 → intermittent sound after ~30 seconds, then mute,
– replacement IC #2 → no sound at all.

This could mean:
– the replacement IC’s are fake / reclaimed / defective,
– or they are more sensitive to an existing surrounding circuit problem.

At this point, I personally would not continue buying more TDA1305T IC’s before doing more measurements around the original IC.

I think the important next diagnostic step is determining:
Does the audio already disappear directly at the analog output pins of the DAC, or only later in the muting/output stage?

That would help confirm whether the DAC itself is really failing.

I would suggest checking:
– DAC supply voltages before and after audio disappears,
– BCK / LRCK / DATA signals,
– mute line / muting circuit,
– analog output directly on the DAC pins,
– freeze spray / thermal testing on the DAC and surrounding components.

To me this still feels more like a surrounding circuit or thermal issue than a confirmed pure DAC failure.

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

Thank you, that information helps.

Since it is a MK3, at least we know the technician is working with the correct service manual and the correct DAC type (TDA1305T).

However, the behaviour still does not fully convince me that the DAC IC itself is the primary problem.

The fact that:

• the CD continues spinning correctly,
• timing continues normally,
• and the audio first becomes intermittent before disappearing,

still sounds more like a thermal or surrounding circuit issue to me.

Possible areas worth checking:

• power supply stability around the DAC/audio section,
• voltage regulators,
• electrolytic capacitors,
• mute circuit/transistors,
• solder joints or hairline cracks,
• temperature-sensitive components around the DAC stage.

Especially because the failure develops after some operating time.

A useful diagnostic step could be freeze spray / controlled heat testing around the DAC and surrounding circuitry to see if the behaviour changes immediately.

Questions

1. Does the sound always disappear after roughly the same amount of time?
2. And does it return again after the unit cools down?

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

I am not fully convinced yet that the TDA1305T itself is the root cause.

The fact that the CD keeps spinning and timing continues, while only the audio disappears after 1-2 minutes, could also point to a thermal issue, power supply instability, muting circuit, soldering problem or an issue around the DAC/output stage.

Also, the different behaviour with the replacement IC’s does not automatically prove they are fake.

One important question:
Which version of the Beosound 9000 is this exactly? MK1, MK2 or MK3?

There are differences between revisions/boards and that may matter here.

Do you know:
– the exact type / MK version?
– whether the service manual matches this unit?
– if the supply voltages around the DAC were measured when the sound disappears?
– if the mute signal changes state when the audio drops out?

To me this still sounds more like a surrounding circuit issue than a pure DAC failure.

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

@Adams

Thank you very much for sharing your experience. I haven’t had the opportunity to compare all the BeoGram models, and experience their differences.

So, this information is welcome!

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

@Adams

Interesting comment.

How would you rate the BeoGram 4000 series, compared to other (later) linear tracking turntables, and radial tracking turntables?

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

A warm welcome to you Michael !

Great you got the virus too. And by the way, your story brings back to me the ‘triangle of top designers’.

• Braun design s became famous because of (the great) Dieter Rams.
• Apple’s top designer Jonathan Ivy was inspired by the designs of Dieter Rams. There’s a famous list of Apple products derived from Dieter Rams’ / Braun designs: https://sl1nk.com/fVgIa
• Jonathan Ivy also was inspired by the B&O designs, especially with aluminum, which is obviously recognisable in most Apple products.

So, going from loving Braun to loving B&O is quite logical. Enjoy it!

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[KolfMAKER]

Dear Daphne,

I get that.
Your Beolab 8000’s were manufactured in 2002.
With this serial number, they are MK1. (serial number 1699 2475 and above are MK2)

Best,

 

Location: The Netherlands

Favourite Product: BeoSound 9000

My B&O Icons:

[Author]

Posts