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I would like to refresh that old thread of mine, still unsolved!
Here's my problem: I can't tune above around 92 MHz, after which frequency control is lost and the whole FM band is scanned very quickly - I can hear radios very briefly - and that's it, static, stuck at 108 MHz, but still displaying 92. I have to manually go all the way back to 87.5 to get control back. I want to precise that the counter works because if I turn the wheel I can display any frequency and it stays there.
Any ideas please?
The video shows the problem at 97 MHz, so this has worsened with time...
Format: MOVDuration: --:--
Jacques
This is the Beomaster in which we tested another pair of tuner boards, correct ?If so, I am almost sure that this is a processor problem since the tuner basically iscontrolled by the "up/down/fast" signals from the CPU and I am sure you will see the voltage onthe collector pin of 1TR1 run astray as well.Can you provide a photo of the processor module and also one where all lettering on the two CPUs is visible ?
Martin
Dillen: This is the Beomaster in which we tested another pair of tuner boards, correct ?
This is the Beomaster in which we tested another pair of tuner boards, correct ?
Yes, correct.
Dillen: I am almost sure that this is a processor problem since the tuner basically iscontrolled by the "up/down/fast" signals from the CPU and I am sure you will see the voltage onthe collector pin of 1TR1 run astray as well.
I am almost sure that this is a processor problem since the tuner basically iscontrolled by the "up/down/fast" signals from the CPU and I am sure you will see the voltage onthe collector pin of 1TR1 run astray as well.
That's the case indeed. The processor module is closed at the moment, in the BM, but here are the photos of the actual PCB, unfortunately with no view on the processors themselves.
I've found that:
http://beolover.blogspot.fr/2013/09/beomaster-frequency-counter-feedback.html
Same experience, same scope readings basically if memory serves. I replaced the prescaler two years ago, to no avail. So my problem is different, and perhaps processor-related.
Hi,
I'm still looking for a spare microprocessor module donation.
I now cannot tune on anything past 91 MHz, so the situation is worsening. At the beginning of the problem, it was 97, then 102 for a few months, yesterday, 92 and now 91.
All other functions of the Beomaster work as they should.
This is very puzzling.
That is pretty odd. It seems like something is interfering with the signal between the tuner board and the microcomputer board though. If the microcomputer (IC4) was bad it I think it would just stop working altogether, not slowly deteriorate. That is just a guess of course so I could be completely wrong. I know when I refurbished my BM8000 and broke a lead on the L2 component of the microcomputer board that killed any chance of tuning an FM station. Once I fixed that inductor/transformer, everything started working again. That makes me think something involved in that path might be the culprit. I'm afraid I don't have a spare microcomputer board but be patient, I'm sure a donor part will eventually be found. If you were in the US I know of a guy selling a used BM 8000 in Denver. It would be way too heavy to ship to France I think.
Thanks for your thoughts John.
In fact when I monitor the processor's pulses at pins 19 and 20 I can see it go astray at the same frequency.
There must be something wrong in the loop, not the tuner - this was checked by swapping the whole tuner section - but somewhere on the processor module.
Hi Jaques,
do you have a frequency counter or can get one for a short time?
To check the divider part on the microprocessor board you can check what frequency range the processor gets offered when manual tuning. You should get a readout of about 384 KHz for 87,5 MHz and about 464 KHz for tuning to 108 MHz. This verifies the correct function of the prescaler (part of the loop). Check the voltage at pin 1 of the prescaler chip µ264 you should read about 3,3 V (always at 87,5 MHZ as well as at 108,0 MHz and in between).
The tuner module as the second part of the loop is also already checked as you wrote. so there are two parts left: The processor itself and the tuning voltage converter
All this checking should be done with 'AUTO TUNE' switched off so that you get as much control as possible over the loop.
Ralph-Marcus
Thanks for that, Ralph-Marcus.
No I don't have a frequency counter alas, nor can I get hold of one, and I must admit that it's a problem.
I can confirm that I do get a firm and constant 3.3 V at pin 1 of the prescaler.
The voltage converter has been checked too.
The tuning voltages are normal at 87.5 and 108. Only it jumps from 93 to 108 in 2 seconds.
Also, I remember that injecting tuning voltage from external variable PSU makes the tuner work normally, with no drift control of course.
By the way, why on earth is the flip-flop divided into two 4013 chips?
on the pics of the processor board you posted i only can see _one_ CD4013 on a seperate board connected with 4 wires to the main processor board The CD 4013 contains two D-Flipflops inside which are connected to each other so that every flipflop divides the signal at its D-Input by two and both together divide by 4.
Bad that you don't have a frequency counter, but maybe you have an oscilloscope?
Applying a manual tuning voltage to the tuner should give you a visible frequency sweep on the screen of the scope when changing the voltage from low to high and vice versa. This sweep will be shown by the highs and the lows getting narrower when 'tuning' upwards and getting broader when tuning downwards.
At PIN 3 of the CD 4013 you should get the half 'pitch' of the pulses (= frequency at PIN3 will be divided by 2) compared to PIN 1 and at PIN 13 the 'pitch' should be doubled ( = frequency at PIN 3 divided by 4).
I doubt that the processor itself has a fault because every other function it controls works fine as you stated before so it's 'only' counting that world go wrong. As long as the basic function is working (and it does from 87,5 - 93 MHz !) there can only be a missing or malformed clock signal at PIN 21 of the processor IC3 This will be interpreted by the program for the tuning that the tuning voltage is to low to get the wanted frequency and therefore it decided to raise the voltage even more and also fast (IC3 PIN18 going Low) to it's limits (which is 19,5 V by design giving 108 MHZ) resulting in the fast tuning to the maximum within 2 seconds.
When tuning down getting nearer to the 'magic' frontier of 93 MHz the processor suddenly gets an frequency which matches the expected frequency and the loop is closed and stable.
So checking the frequency at IC3 PIN21 and it's origins towards the base of TR5 should help to isolate the fault.
Replacing the CD 4013 should be a first step. It can also be named HEF4013 or MC4013 all are CMOS Chips containing two seperate flipflops in one case. Try also to replace the wires connecting the additional board to the main board or check atleast the continuity of them from board to board maybe cracked wire or solder joint.
I've got the CD4013s so I'll do that first.
I do have a scope!
Thank you so much for the compehensive explanation!
Jacques, Can you post some pictures of your test connections and your measurements as you go? It will be a nice reference for future Beomaster 8000 work. :)
sonavor: Jacques, Can you post some pictures of your test connections and your measurements as you go? It will be a nice reference for future Beomaster 8000 work. :)
Yes please, and Ralph-Marcus, thank you for your clear explanations, even I understand it.
Collecting Vintage B&O is not a hobby, its a lifestyle.
First of all, I'd like to say that I'm sorry.
Sorry, because I did not have to measure anything more. So, nothing to show.
I know, this is frustrating.
I'm sorry, again.
THE THING WORKS! THE PROCESSOR IS GOOD!
A replacement of the two flip-flop CD4013 has cured the Beomaster completely. I don't know which one was at fault, but there.
How did Bruce Willis put it already?
Anyway, thanks to all, Martin, Søren, John, always supportive of our efforts, real friends, and particularly to Marcus-Ralph who convinced me that the μP was fine.
Wow, this is my two thousandth post
Great news Jacques. I'm glad to hear your Beomaster 8000 is back in working order. I use the one I refurbished last year almost everyday. I have one, maybe two, more that are waiting for me to repair so I am always interested in the problems and solutions other BM8000 owners run into.
Congrats on your 2000 plus posts, and keep them coming, I am on the forum just to read your posts.
Søren Mexico: Congrats on your 2000 plus posts, and keep them coming, I am on the forum just to read your posts.
And me, yours!
Congrats, Jacques, on fixing the BM8000 at long last.
Also, congrats on Post 2000. I, too, reached that milestone not long ago.
Thanks, well, you know the feeling! How many times I've opened that can I wonder!
Trying out...
The little rascals...
Congratulations Jacques! This is really great news! I'm glad that you finally found a way to fix your BM8000.
I had a spare microcomputer board, but as I had a BM8000 with the same fault as yours, I needed it myself. Besides that I think the one I have is a different version, and the two versions aren't interchangeable as far as I've understood. I still have the faulty one, so maybe I'll have a go at fixing it some time!
/Dennis
congrats to your finally 'new' BM8000 ! Also to your endurance in fixing this nice beast :)
What makes me wonder are the two CD4013 chips in the divider chain. According to the circuit diagrams available here at beoworld.org there's just one 4013 using both flipflops inside.
You have a nice collection of B&O icons!
chartz:Thanks, well, you know the feeling! How many times I've opened that can I wonder!
RESULT
Wow !
I was so happy when I saw the "solved" mark after the topic title ! I know how you must feel after all this time... I'm really happy for you ! Great patience !
I do hope there's something really interesting above 92MHz to listen to and celebrate !
Félicitations !
Guillaume
RaMaBo: What makes me wonder are the two CD4013 chips in the divider chain. According to the circuit diagrams available here at beoworld.org there's just one 4013 using both flipflops inside. You have a nice collection of B&O icons!
Thanks, only the tip of the iceberg! The odd one out here being...? Probably the best built CD player I've ever come across...
There are two 4013, the one you obviously see on the piggy PCB actually uses only one element in series with the other two. On the first pic the other one is hidden underneath the connection wires to the piggy board (bottom right of it).
Also, some techie had disconnected the TMS - he cut off two pins - why? Programming worked fine again after fixing that.
Here's a second view:
Now, why it failed is another matter! But it is not always obvious why components fail. Sometimes, they just do, don't they?
Ah, okay it's a better picture than the old one you posted yesterday.. Now the plastic stripe with the cooling paste has been put away and reveals the 'missing' 4013.
Maybe the same mod B&O did for the BM6000 processorboard once.
But 'modifing' the TMS storage chip is reallly very difficult to understand. But you finally found this error too and now have a fully working beautiful piece of designing art from the eighties. Congratulations!
As an aside, can anyone explain to me why the Beomaster 8000 is lacking, compared to the 6000, the 4400, or the old Beolab 5000 (the best in my opinion) for that matter?
It's fully re-capped (Elna Silmic II in the audio path).
There is less air, everything seems to be a bit less finely etched, a bit flatter. Reverberations lack depth. The bass, however, is prodigiously well-controlled.
Too many op-amps?
I have replaced the amp "from the drawer" 4.7 µF input caps. They sounded bad, although new. The brand is Lelon.
Yet another opening-the-BM8000 session. Oh well!
However, I still prefer the sound of the lesser Beomaster 6000. Does anyone share the same experience?
Congrats on finally fixing your BM8000 Chartz!
About the sound: one difference from BM4400 to 8000 is the change from mechanical to IC-switches. The signal goes through 2-3 switching IC's in the BM8000.
I never used the filters on my BM8000. One day I thought, why not bypass the switching IC then? So, as an experiment I took out the filters switching IC on PCB4 and soldered in a wire. Result: clearer sound, more definition in bass. I have since changed all the switching IC's for mechanical relays. I really like the resulting sound, it is fresher, less muffled. Would like to do a comparison someday with a non modified BM8000, but first I'd have to find one!
chartz: No answer... I have replaced the amp "from the drawer" 4.7 µF input caps. They sounded bad, although new. The brand is Lelon. Yet another opening-the-BM8000 session. Oh well! However, I still prefer the sound of the lesser Beomaster 6000. Does anyone share the same experience?
No answer... I have replaced the amp "from the drawer" 4.7 µF input caps. They sounded bad, although new. The brand is Lelon.
Sorry Jacques,For me that is tough to answer. When I started my vintage audio hobby and ended up with a variety of speaker types, amplifiers (and other components) I thought I could finally set up comparisons between them. I can set up various combinations of course but actually doing a good comparison is too hard for me. I find that my listening memory between setups just isn't that reliable. In switching from one set up of nice equipment to the other I find myself just enjoying the music coming out of the system. Sure I have set up some A/B (and C) switching of speakers and can tell a difference...but I find it hard to choose a winner. I find the Beomaster 4400 and 8000 produce very good results. Right now I prefer the 8000 because it I have it set up as a full 8000 system. In my workshop though I have a Beomaster 4400 and listen to it quite often. I need to get my BM6000 fixed up and working again. Hopefully I can get to it this year. In my office and bedrooms I have a number of other systems I listen to quite frequently. I just can't pick a favorite.
-sonavor