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Beomaster8000 repair/resoration

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ALF
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ALF posted on Thu, Mar 21 2019 8:53 AM

greetings ALL 😁

I decided to start a new thread with my new donor-unit BM8000 - this time in the correct forum !

this donor unit was purchased as a parts-reservoir but turned out in very nice cosmetic condition.

so I took a close look and noticed all boards were recapped, the displac is fine....well, so far so good.

further testing reveiled there are issues:

Plugged in it shows the StBy dot.

turning on, no relay clicking while the display comes on.....hmmm ?!

checked the power supply board....all associated transistors have tested fine off-board, all caps are in the correct way, all connector joints have been reflown.....?!

next thing I noticed the small heatsink with the 3 voltage regulators is getting VERY warm....?

next thing : with no relays energized I can measure the 15V and -15V regulator which should only be possible

when the start-up circuit gives the “green light”.

5V should be present at Pin14 / 9IC4 during STBY mode and going down to ‘O’ when ON is achieved....no, it remains at about 25mV

meaning: the BM according to this is actually out of ST BY !!

5V are only present at the 5V regulator when I disconnect P76 of the processor board ?

a faulty processor 9IC4 ??

I did change the two 2MHz crystals (as suggested as a precautional measure by Beolover) after removing 

both uPs for safety reasons......! No change !

I disconnected the keyboard in case the on/off key is stuck and used the remote to turn off/on  the BM....

no luck here either 😡

disconnected P51 and 50....no change.

well, what am I missing here ?

and this is only unexpected work at the donor-unit while waiting for those speaker switch replacement to

continue work/repair/restore on my original BM8000 project...😳

guess help is badly needed here 🙄

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ALF
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tricky to capture - hope you can see the difference on the imprint on the two ICs:

 


Dillen
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Dillen replied on Fri, Apr 19 2019 6:26 AM

Lettering is printed. Should be laser-engraved.

Counterfeit, I'd say.

Martin

 

ALF
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ALF replied on Sun, Apr 21 2019 2:43 AM

I can’t possibly speculate whether those AD7110KN attenuator chips are a “popular source” of vol7me issues  ?

disappointing, it is such a pain to find some good parts these days - practically everything seem to come out of China - there is no real supplier choice !!

I gave it another go from a different (chinese) supplier 🙄 and ordered some more AD7110 ICs. Everything seem to point towards the 

tone/filter board and its volume attenuators....can’t think of a different problem source unless all power transistors in both channels are dead....

but then the fault switch would become active .....or is it ?!

let me repeat:

all interconnecting cables/connectors are fine - appropriate volume signals are coming through from the uP board to the tone/filter board, both attenuator ICs are getting the vol signals!

any other ideas......?

ALF

ALF
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ALF replied on Tue, Apr 30 2019 10:58 AM

Hi everyone,

back on the job finally delivered a win.....

one question remains: what is a stupid mistake ?

I dare to say there isn’t one as we all do “those” in moments of distraction, frustration, tiredness ect......

gone back to the SM and its table of interconnections between boards - rechecked the wiring again....guess what ?

4P27 was connected to the wrong plug !!! 🤬 which was the reason for the “volume issue”

for now one of the two patients BM8000 is working fine and enjoying life again  — 🤗

the work now turns to the other BM8000 with the obvious similar “volume issue”.....no, all interconnections are fine 😬

which brings me to the last comments and replies about fake ICs....a new lot of volume attenuator chips AD7110 is coming

as this time it looks as the problem is on the tone/filter board ?!?!

again, the volume can be turned up and down with corresponding numbers on the display but nothing but a hiss is audible ?

will get back with some more news once the second lot of good “fakes” AD7110 has arrived.

in the meantime don’t hesitate to reply with alternative pointers or suggestions....

thank you

ALF

sonavor
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Hi Alf,

I'm glad you got the one problem sorted out. On my Beomaster 8000 restoration projects I started labeling both ends of all the connectors. Going by memory was not cutting it for me and it is much less stressful to just read and match the connector number on the cable with the board....with the exception of the preamplifier board which had no room for B&O to print any connector labels.  While most of the connectors have keys there are two or three that have the same key and can be connected wrong, as you found out. 

John

Craig
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Craig replied on Tue, Apr 30 2019 5:50 PM

I take lots of pictures at each stage of the strip down.....and before too, always helps

craig

Saint Beogrowler
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Craig:

I take lots of pictures at each stage of the strip down.....and before too, always helps

craig

The absolute truth right there. And thanks Craig for sharing your pictures as you have been.
chartz
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Remember the time when we actually drew before taking apart?

Stick out tongue

By the way, was the chip indeed a fake? Good to know.

Jacques

Craig
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Craig replied on Sun, May 5 2019 9:42 AM

Actually I sometimes still do......though I take a lot of pics from different angles, in my work I used to do a lot of site surveys and make lots of sketch's....now the digtal camera does all of that, and the pics get embedded in reports etc.

Craig 

mdockrell
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am waiting for a Beomaster 8000 to arrive so am following this with interest. Seller claims is working perfectly but we shall see. 

mdockrell
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am waiting for a Beomaster 8000 to arrive so am following this with interest. Seller claims is working perfectly but we shall see. 

ALF
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ALF replied on Sun, May 5 2019 12:32 PM

Hi,

I wish you luck - one learns a lot about these receivers if it is a ‘to restore unit’ 🤗....but I am not saying yours will be one 🤞

 

with the help of some of our treasured experts I revived two....one is still in intensive care.

still fighting the volume issue - one of the problems is getting the genuine ICs without wasting time and money on fakes......

Luckily I have another donor unit coming to exchange some boards to see what exactly  is playing up....

still chasing some genuine AD7110KN ICs - my second delivery was labelled almost beyond recognition, meaning another delivery of fakes 😡

again I have gone over the tone/filter board, where quite obvious something is not as it should be....

gently!! tapping on P28/29 connectors responds with a horrible crackling noise.

both interconnecting flat cables (P28/29 to uP board) were fine, no wire-break, all showed healthy resistance.

all solder joints look healthy as well - I don’t want to remove the two IC sockets for the AD7110KN pair - that should not have any impact

as both are soldered in perfectly!

anyhow, thank you all for your interest in the problem...

ALF

ALF
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back to the Tone/Filter board,

something that seemed odd - can't imagine that would be original ?!

first two pictures (solder side & component side) show cut tracks between Stereo and Loudness switch and "fly wireing" between those switches

but why ??

 


ALF
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solder side of cut tracks


ALF
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the next two pictures show a cut track of the Signal switch and the 'fly wireing" from the Signal switch D18/D17


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