[Glitch]

Going from memory so I might be off a bit… Check the wire connections between board 5 and 6 for cracked solder joints. Adjust the volume control trim pots on board 6 per the service manual. Clean or replace any trim pots that don’t adjust properly. Make sure that the plastic film display slider window moves freely. I may have missed something, but what this should be a decent start.

Replacing the belt with a new one from Danish Sound Parts would be good preventative maintenance. The belt is the weak link in the design and a new one will save you headaches.

Glitch

[Glitch]

It is good to hear that you are making progress.

Have you hooked up an oscilloscope to the display strobe pins (13-16)? If so, what are they doing? The strobe signals are usually a good place to check for signs of life in the CPU.

marcham wrote:

I was able to track down the issue for my last problem and now have my +15V, -15V, and +5V rails.

What was the issue with the voltage rails?

Glitch

[Glitch]

That is a very generous offer.

I might be interested in them. I’m a sucker for fixing up orphaned electronics and re-homing them. Sometimes I pass it on to a friend or acquaintance, for free or for the cost of parts, other times I donate it to charity (which also may be an option for you if there aren’t any takers).

Where are you located? Send a private message if you would rather not answer in public.

Glitch

 

[Glitch]

Looks nice so far.

Have you considered making the glass/plywood piece out of granite? A countertop shop might be able to do this at a reasonable price using off-cuts. Just a thought…

Glitch

 

[Glitch]

hcraig244 wrote:

Yes the saucepan is simply a convenient diameter to rest the speaker on during removal of the dust cap and drying time of the epoxy, keeps any pressure off the cone and coil.

When I saw the cone in the pot, along with the comment about softening the glue, I was picturing heating the glue on the stove top. I have to say that I’m a bit disappointed that the real answer is less exotic. It seemed like it might have been a opportunity to learn a new technique. LOL.

I’m looking forward to seeing the final, successful repair.

Glitch

[Glitch]

Looking good.

Can you provide more detail about how you softened the glue on the dustcaps? Is the pot part of the process or just a convenient  holder for the cone?

Glitch

[Glitch]

Thanks for the explanations. They make sense to me.

Madskp wrote:

I think it is actually a 2.5mm jack and probably only with two pins (I will look further into that). I do no have that much knowledge about IR emitters, if they have to be for a certain frequency. The Code converter manual mentions a cable with mini plug and a blue LED.

I would expect that certain IR wavelengths would make it easier for the receiver to pick up the signal. At point blank range, there is likely enough “bleed through” or overlap for not perfectly matched parts to still work. I recall reading the B&O had issues with sunlight falsely triggering some systems and having to all physical light filters. I don’t remember what systems were affected, but removing any filters for testing might help. The blue LED comment doesn’t make sense to me since this is at the wrong end of the light spectrum. Unless blue was used as a indicator for a human to see the activity without interfering with the IR.

Madskp wrote:

The MCL Beolab Kit is used to get data control signals from MCL82 or MCL30 link rooms into a BM8000 or BM6000 as none of them have the MCL data connection.

I’m glad to see your picture of the MCL Beolab Kit. I’ve read about it but have never seen one for sale. Maybe the lack of labeling on the box is a factor in this. People might not have a clue what the box is and just toss them out of frustration. Maybe I need to expand my eBay searches to include “unmarked B&O black box”. 😉

I’ve also wondered if it would be possible to bypass the IR stages and hack the MCL signal directly into a BM8000/6000, possibly on the REMOTE pin of the CPU.

Madskp wrote:

Just did a wire up of a MCL82 box with IR tranceiver and the MCL-Beolab kit.

Interesting test. Have you considered hooking up a oscilloscope and comparing any of the signals to the code tables in the service manuals?

Madskp wrote:

I do not have anymore ideas for testing it right now as I do not have any of the other remote types and/or music systems for this to work with. I still have it wired up so can try to test something if you have any ideas

I’m in a similar situation with having some, but not all that is needed to run a good test.

I think that I’m getting motivated enough to buy a Beomaster 5000 and MCP5000 for test purposes. It wouldn’t be the first time I’ve done something like this where the tail is wagging the dog. My Beosystem 5500 stack started with a MCP5500 that was tossed in (for free) in a equipment bundle. The funny thing is that after completing the stack, the original MCP5500 was swapped out for one in better cosmetic condition. Yes, it is a sickness.

Glitch

p.s. I’m jealous of your pile of cables. 😉

• This reply was modified 2 months, 2 weeks ago by Glitch.

[Glitch]

I hope that I’m not hijacking your thread. If so, I’ll “cease and desist” and maybe start a new thread.

I was vaguely aware of the ability of using the MCL82-2041 with the Beomaster 8000, and also the Beomaster 6000 of the same era. The functionality gained for these additional devices seems minimal. My (likely incomplete) understanding is that it just supports a subset of the remote commands that are relayed via a IR->wired->IR chain. The documentation that I’ve found isn’t exactly clear and concise. I’ve found this old thread, https://archivedforum2.beoworld.org/forums/p/14327/126573.aspx which answers some questions.

Madskp wrote:

And now it gets interesting. The next box is also without markings, but I have a feeling it could be a MCL-Beolab kit type 1006/1007 for control of Beomaster 6000 and 8000 with MCL30 and MCL82. I hope someone can verifiy if that is correct? The IR eye is missing.

It looks like the port for the “IR eye” is a simple 3.5mm jack. If so, do you think that a generic IR emitter would work? It seems possible if all it needs to do is pass IR commands into the BM8000.

Could the box be the “code converter” mentioned in the old thread?

Glitch

 

• This reply was modified 2 months, 3 weeks ago by Glitch.

[Glitch]

I got this as a part of a bundle of other B&O stuff. I hadn’t given it much thought until I saw this thread. It appears to be unused since the display still has the protective film attached. I don’t think the original owner knew what it was for and I’m not that much different. Anyway, here is a picture of the circuit board in the off chance that it is useful to you.

Is this useful for hooking up to anything other than the equipment listed on the diagram?

Glitch

[Glitch]

I recall seeing a post where the person built a new suspension out of generic parts. You may be able to find it by searching both the current and the older forums.

Glitch

 

[Glitch]

Dillen wrote:

Would the main problem be reflections of the sound produced by the needle playing the record, or acoustic feedback from the speakers to the record?

I think their proposition is that the sound waves are driving the turntable chassis, which in turn makes its way into the cartridge. I could be misinterpreting this.

The problem with trying to run something like this as a “mental experiment” is that one doesn’t know the contribution of each part of the turntable. For example, how much effect is from the sound waves hitting the record/platter? One could argue that lid down would block the waves from reaching the platter. But lid down could also increase the overall surface area and in-turn the total energy going into the chassis. It isn’t that hard to come up with many more similar combinations, none of which anyone has the answer for.

It also depends on the particular equipment that one is using. I would guess that a lightweight turntable would be more susceptible to these kinds of issues than a heavy one. However, I don’t know if the issue is really an issue on either one. That is why it is important to test your own equipment in your own environment.

It seems that the cartridge suspension response versus temperature would be easy enough to test. Run the frequency response test from a frequency sweep on a test album, record the results, run a FFT. Next do the same at a different temperature. Lastly, rerun the first two test to verify that they are repeatable. I’m confident that there will be a difference since it is well known that the characteristics of rubber change with temperature. However, I wouldn’t be able to say if the difference is perceptible. Even less, I wouldn’t able to say which one is actually “better” since “better” is subjective.

Playing devils advocate… Are most people brains wired to assume the warmer physical temperatures are correlated to warmer music tone?

Glitch

 

[Glitch]

It is important to distinguish between “different” and “perceptibly different”. Pretty much any time one makes a change, it will be “different”. This even includes items that were meant to be the same. It was not surprising to me that the three lids positions had different results. What isn’t clear is if any of them are perceptibly different.

What I believe that the test needed to show is a comparison between the noise signal (i.e. the lid/chassis resonance at the cartridge) and the equivalent cartridge signal. The measured relative difference between these two is important. There are many studies that define what a typical human can differentiate. Something like this https://www.ussi.com/acoustical-rules-and-demystifying-decibel.php (this was simply the first hit I noticed on Google).  The good thing about running a test like this is that it takes the monkey out of the loop.

My postulation is that, at typical listening levels and room acoustics, the level differences between the signals, lid up/down/off, are lower than can be perceived. The problem with human judgement tests is that people will “hear” what they want to hear. Sort of like the audio equivalent of “these are not the droids you are looking for”. 😉

I have very good hearing, but I don’t trust my brain to get it right. This is because I’ve tried running a test myself, then getting help from others and running a similar test double blind. The results were different.

Maybe someday I’ll try to run my modified pro-jectusa test and know for sure.

Glitch

[Glitch]

Giorgione wrote:

Easy to setup? How? I don’t think I have the gear to do that – only the ear, ha ha. I don’t pretend my test to be objective but if it sounds better to me either way it’s still meaningful, to me at least. I also think that most parameters remain the same, whether doing a hearing as well as an instrumental test, the only variable being the lid.

One would already have most of the equipment needed for the test as part of their normal stereo system. Additionally, a multimeter and a phono preamp would be needed to take the reading from the turntable. The phono preamp linearizes and amplifies the signal from the cartridge. The amplified signal should be large enough to measure with the multimeter on the Vac setting. MP3/FLAC test tones would provide the source tones. The only other thing needed is a fair amount of patience to take and record the readings.

I would expect that you will have a difficult, if not impossible, time running a meaningful subjective test. I won’t go into all of the details, but Google something like “A B audio test pitfalls” and you’ll find plenty of info. In addition to the things typically listed, you will also have to deal with echoic memory in the relatively long time it takes to switch lid positions.

I guess in this case, “easy” is a very relative term ;-).

Glitch

 

[Glitch]

etype76 wrote:

I also thought that the slanted lid was simply part of the design. Whether it had beneficial effects on resonance was likely coincidental.

My slanted lid comment was made in jest. I’ve always imagined that there was a rivalry (friendly or not) at B&O between the designers and the engineers. It seems like a significant amount of the engineering innovation was a result of overcoming the compromises dictated by the styling. This seems most evident in the speakers made between the 1980’s and 2010’s.

Giorgione wrote:

I’d like to hear opinions/findings/speculation/test results about these alleged disturbing resonances transmitted via the lid

Have you considered duplicating the pro-jectusa test? This seems like an easy test to setup. You would also have the benefits of testing at the listening levels that you normally use along with your exact equipment location and room acoustics.

I don’t put much merit in other people’s “listening tests”. There are too many possible variables that make any results meaningless.

Glitch

[Glitch]

Giorgione wrote:

My furniture is anechoic and because of my fabulously furry body, I’m a nude listener.

LOL

 

I think that the stereotypical B&O owner has different priorities that the stereotypical audiophile. For example, I can’t recall ever seeing a Powerlink cable that featured high purity copper, varying gauge strands within each conductor, opposing conductors pairs having left and right hand twists, Teflon insulation, 24K gold plated connectors, all double cryogenically treated. I’m sure that many of B&O’s customers have the means to buy such a cable, just not the desire.

etype76 wrote:

This is what Pro-Ject have to say if graphs is your thing:

Interesting article. I wonder how loud they were playing the test tones (at point blank range)?

Does this explain why B&O featured slant front covers on some turntables? Like radar reflecting off a stealth fighter…

Glitch

 

[Glitch]

matador wrote:

Link please…

I can’t tell if you are serious. I just googled “fuzzy jumpsuit” and picked the picture of the fuzziest one. 😉

As far as the lid up/downs goes. I always assumed that picking up a piece of dust on the stylus would have a bigger effect than anything else. Even considering that, I’m more concerned about the damage to the cartridge related to messing with the lid. Lid down for hinged lids removes the possibility of the lid slamming shut. Lid off for unattached lids to avoid bumping the tone arm.

Glitch

 

[Glitch]

My personal preference is to have anechoic furniture and wear one of these when listening to music. 😉

Seriously though, if your equipment/music elicits a physical (goosebumps) or emotional (happy or sad feelings) response, then it is doing its job.

Glitch

 

[Glitch]

Send an inquiry to Danish Sound Parts. Most likely, they will be able to find a used, working CPU for you.

Glitch

 

[Glitch]

marcham wrote:

As someone who doesn’t know exactly how a circuit flips a voltage from 15V to -15V, I would say that something looks a bit off around TR18, even though that transistor tested well. But, again, what do I know? 🙂

The circuit doesn’t “flip” the voltage. It regulates from the negative side of the bridge rectifier. You have -23v there so you are off to a good start. I’m not sure exactly sure what TR18 does. I’d have to think harder about the circuit than I’m willing to do right now. I believe that the key to your solution lies with the base of TR21. It should get pulled high by the CPU and enable the -15 supply. Verify that the connection between the two is solid.

As always, I could be wrong. I have a faint recollection of the POWER OFF/ON signal also controlling the +15v power. I could also be thinking of another piece of equipment.

Are the voltage measurements taken in ON or Standby?

Glitch

 

[Glitch]

A general initial checklist…

1. Verify the polarity of the capacitors that you swapped
2. Check the connectors for cold solder joints and reflow if needed. You may have opened up something when you were handing things
3. Verify voltages at the power supply and on the CPU board
4. Adjust the reset circuit EXACTLY like stated in the service manual

The machine working before you started is a good start. However, you had to “look at the machine” to do the capacitor swap. It seems that sometime that is all that is needed to break a Beomaster. 😉

Glitch

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