Yes, what I meant was that if the readout is correct, as in corresponding to the actual tuned station, the prescaler is probably fine.
The displayed frequency is the ordered frequency rather than the measured (or the readout above 97MHz would have shown up
irregular in your case).
If they don't match, the CPU corrects by sending adjustment orders to the tuner.
When you unplug P84, in other words you "introduce a prescaler fault" the actual tuned frequency and the frequency readout no longer corresponds.
(And if monitored, you would see the processor issueing orders to the tuner to get the tuning correct - to no avail).
But it's a closed loop with several possible faults and the prescaler can fail in many ways so I suppose we still cannot rule it out completely.

Martin

Thank you Martin. 

Do I have to replace the white thermal compound? It is still very viscous, and there's a lot of it!

I should receive the new chip tomorrow. Let's see if it does it. I examined everything again, and the PCB looks fine, but it is slightly twisted/bent on the right side. I have replaced the electrolytic—while the can is open!—but the old one was okay I guess.

There are lots of added wires and caps on this PCB!

Note the missing chip! The red wire was already melted!

Hi everyone,

I am sad to report that what Martin said was right (of course, I hear you say). Replacing the U264B chip didn't make any difference. Since I have re-soldered all the connectors, the ones linking the two tuner boards included (with permanent wires these) I am at a loss now.

The problem: past 97 MHz, the tuning voltage goes up to its maximum (23V) by itself, I can hear the radio stations briefly, then I just get white noise (what some call static). The frequency display goes all the way up if I continue to turn the wheel. Same phenomenon going down, the max voltage unlocks at around 93 MHz. 

On auto tuning though, the display never goes beyond 97, unless I make the wheel turn veeery fast.

If anybody had an idea, let me know please!

Jacques there is a proceedure in the manual to help the technician isolate the fault to either micro or Pulse height modulator side but you need an RF signal generator and scope. Have a look toward the end of the manual somewhere...

chartz:

Thank you Martin. 

Do I have to replace the white thermal compound? It is still very viscous, and there's a lot of it!

I was always under the impression that too much thermal compound actually impedes thermal conductivity. I have been surprised by the amount of paste B&O slap on to their output stages but I was even more shocked when I saw this! I am personally going to do something about it but not sure quite what that is yet!

Well, I don't have an FM signal generator.

What next then? The CD4013?

Hello everyone!

On Martin's advice, I'm about to replace the LF353N op-amps, and the 22V zener. I've made a stock of BC transistors as well, just in case.

Let's see what happens...

Good luck!

Thanks Olly.

You know, I think this Beomaster actually sounds better than my 6000. I know it shouldn't, but it does. I just love its sound. Pure joy with the CDX. It will stay, and sadly the little brother will have to go. I won't sell it, no. I also like the fact that it stays very cool (unlike the 6000 which is always lukewarm).

I use MC120-2 speakers.

Yes I have S-120's and now some S-80s (need work) Jacques. Must admit I didn't have a cd player as a source when I tested so I might yet see a further difference between the units!

I agree the 8000 has much better heatsinks which I suspect is mostly the reason it runs cooler!

Hi,

I saw on a 'hifi' website that the Beomaster is 'expensive' lo-fi...

I hate that kind of nonsense from people who have probably never heard B&O gear. Having myself heard lots of hifi components (including valve stuff) I don't agree, no Sir! I'm listening to a live programme on France Musique now (Zaza Fournier, a French chanteuse) and it is pure joy here too!

Oh well!

My only problem now (tuner trouble aside) is that my Beolab 6000 shelf won't take it. Damn! Also, what were they thinking when they decided to place speakers DINs so far apart?

Oh well, sounds good enough to me, and will always be far more enjoyable in everyday use than what they would class as 'hifi'.

On a different note, which amp do you prefer in the looks department?

Personally, I think the 6000 is the prettier of the two!

The jury remains out!

The jury has finally come to a verdict: the Beomaster 8000 is the winner , and the runner-up is the Beomaster 6000. I'm still wondering where I'll put it though.

By the way, I'm looking for a Beolab Terminal for the BM 8000. Has anybody got a spare?

I've just found one in an online B&O shop, but € 100, no thanks , I'll pass...

Hi,

Well,

After changing all the LF357 and transistors, I'm sorry to report that the symptoms haven't disappeared.

Damn.

Now the audio LF353 has a holder and I'll be able to test other chips when everything works!

Just kidding, I may be deaf, but I have never heard a great difference between reasonable op-amps or audiophile components. Never have I heard a difference for instance on a CD player audio output chip. But then again I may be deaf. Recently I discovered that capacitors of good quality sound pretty much the same too. I believed the hype. Replacing tantalum caps in my Beomaster didn't change the sound at all. I could have saved both my iron and some solder. But I digress!

Help?

Hello everyone!

I'm still at a loss as regards that Beomaster 8000 tuner failure after 96/97 MHz. I'm pretty sure the tuner itself is fine.

I am waiting for Martin to come up with something (he will I'm sure! ), because my skills here have reached their limits. I spent quite some time on the diagrams but I'm stuck somewhere in the loop. I can't measure anything related to the PC board and the SM isn't very specific (or I'm daft).

Another daft question then: I haven't changed the amps PSU caps on either my Beomaster 6000 or 8000. What gains should I expect there, knowing that both receivers work fine? I have many audio devices which have their original PSU reservoirs and don't hum or buzz!

Thanks.

Hi Jacques, IMHO, with regards to the 6000 I would definately replace the two metal caps on the PSU board, as these it would seem are prone to failure around about this age. Only use good quality 105 degree caps here because of the warm nature of the heatsink! I have actually relocated the capacitors in three units (another one to do) and have found peace of mind that the new replacements should now last much longer!

I would definately look at replacing the 4 large electros in the Beomaster 8000 and possibly the large axial PSU caps (especially the one near the hot regulator!) but back to the 4 large caps these have little headroom with the voltage rating and one of mine was near short-circuit when I recieved it! I picked 80V Panasonics rated at about 8A ripple, I think this is a pretty similar spec to the originals. You can get some very exotic jobbies but they start costing some serious money!

I have yet to start recapping my 8000, as some might have guessed from lack of update recently! I am not in a hurry to do so as I have found that whenever I have recapped this age of hifi and newer, even with audiphile grade capacitors, I have noticed no difference to speak of! Even went to the trouble of having two 6000's next to each other and recapping one, with a switch to change between speaker outputs and noticed no difference! I also recapped one channel, once again no change to write home about!

I also tested all the electros from various hifis with an esr meter and they mostly test fine. I think it is worth doing for peace of mind with this age, especially those that are pushed to their limit either temperature or voltage / current etc. - they are not going to last forever!

I know people here might not agree with my conclusion but so far this is what I have noticed first hand, and I go to quite a bit of trouble to test things in an objective manner!

I am sorry you have not had luck with the 8000 tuner Jacques. I wonder if there would be further help in the manual that accompanies the service manual (mentioned in the latter). Maybe as it is Radio Rally season you could look at expanding some of your test gear (signal generator) for a reasonable sum...? I will be doing this myself this year!

Step1:

I have yet to start recapping my 8000, as some might have guessed from lack of update recently! I am not in a hurry to do so as I have found that whenever I have recapped this age of hifi and newer, even with audiphile grade capacitors, I have noticed no difference to speak of!

I haven't started either, but I've taken a look inside and all the plastic can type electrolytics on the power amp boards are cracked and look like they are literally ready to explode. Never mind if the sound gets better (it does sound like s*** currently), I will replace them...

Thanks for your thoughts Olly and Mika.

Hey, there is no radio rally here in France!

Anyway, the left channel remaining almost cold, I'm going to set the quiescent current. The trimmers were changed in the receiver's life, but I suspect it is too low, although the amp sounds fine, and there's plenty of power.

Even pushed hard, the dissipator won't get hot at all, just a bit warmish!

The right channel is a bit warmer, but I can't hear any difference in sound.

Do your Beomaster 8000 amps run very cool as well?

chartz:

Do your Beomaster 8000 amps run very cool as well?

It does now once I went in there and checked the idle current settings. Before that, the other side smelled like an electric radiator after a while of playing... will replace the trimmers and the caps in the same go sometime later before I actually start using the receiver.

I must be lucky as my 8000 seems to be just fine, but I think you give a good case in showing how some systems can be fine while others are not!

On the other hand, my Beomaster 6000 has been working all day long for two years without a glitch! I've also got a valve amp which I refurbished in 1990 and it has worked fine ever since, with the same valves (6CA7).

By the way, the 6000 does get warm (but not hot), contrary to the 8000. I've checked the quiescent current (left channel) and I get 44 mA before adjustment. A little low then, but it won't get much warmer once adjusted to 50 mA!

Right then. Both trimmers duly adjusted. I managed to get around 50 mA quiescent (idle) current on both channels, but the values were just a little below at 44 and 45 mA, so not far off! As a general practice I like to keep the current a little above the stated values, but here I chose to stick to B&O recommendation. Dc offset is acceptable too, but I couldn't get much below 10 mV, which is okay I guess. I confirm that the fins remain very cool, always. Well I don't run a disco!

I checked for any ripple in the DC voltages, but all is fine here too, although the PSU caps are all original!

I wanted to change the three caps on my BC3500 and I did, but it didn't change anything actually! I think B&O chose the best back then. Wicon anybody? I had never come across these before, being more accustomed to Philips and SIC-SAFCO, and of course Panasonic and Elna Japanese equivalents.

The PSU will stay put for now.

Most amazing, the unit sounds very good compared to my Beo 6000 (fully re-capped with Elna Cerafines, except PSU), with finely etched treble detail and lots of bass (filters off). It has all its original caps!! Yes Sir, even that red ROE at the inputs of the amps!

I have to push treble a little (+2) and bass too (+1) if I want comparable sound on my 6000...

And those MC120-2 amaze me more and more. They will take a lot of power! And they sound super-clear!

About that tuner now.

Hi everyone!

I've downloaded the "Technical Product Information" for the Beomaster 8000.

This is a very comprehensive 41-page book which goes deeper into how the Beomaster works (PM me if interested). It allowed me to understand how the tuner works, but the processor part is not that clearly explained.

I checked the tuner different parts, measured everything, replaced a few doubtful transistors. Everything seems okay at the integrator level, the constant current generator (TR4-TR5) works normally.

The tuning voltages goes right up to 22V past 96.3 (it should be 19,5V at 108).

There's something wrong somewhere in the loop but where? And why does it work normally below the critical frequency?

chartz:

The tuning voltages goes right up to 22V past 96.3 (it should be 19,5V at 108).

That is so odd that it makes me wonder if you should just replace more, sounds like some component has a non-linearity which might not show up in normal tests, perhaps around TR7/D4... How is TR1 and the opamp? Have you tried with no load on the tuning voltage output or with AFT input disconnected?