Sign in   |  Join   |  Help

Beolink 7000 backlight power supply from PCB 1 fault

rated by 0 users
Not Answered This post has 0 verified answers | 23 Replies | 2 Followers

webbda77
Not Ranked
9 Posts
OFFLINE
Bronze Member
webbda77 posted on Sun, Sep 7 2014 12:44 AM

Hi all,

I have a Beolink 7000 that seems to have a backlight power supply issue a step beyond most others described on the forum.

The power supply to the screen (from the black and brown wires) is around 30v AC (and across the coil). 

One of the PNP transistors had obvious signs of heat stress, so I sourced some BD436 replacements and replaced both on PCB 1, as well as the 220uF capacitor just adjacent to the wires terminating on the board hoping that might be the solution. 

So far it hasn't made any difference to the low AC issue for the supply out to the backlight.

Otherwise the remote is working quite well - with battery renewal and IR capacitor replacement the two-way comms to my Beocenter 9500 is functioning correctly, and the motor drive/start up behaviour of the remote is all good, as are the menu functions of the remote - it's just annoying needing a to shine a torch at the screen to see what I'm selecting Wink

The original B&O service manual for the Beolink 7000 is a bit light on detail to help me much, so any suggestions would be gratefully received!

Thanks,

 

Dan

 

 

 

All Replies

Die_Bogener
Top 500 Contributor
192 Posts
OFFLINE
Bronze Member

Hi,

the voltage should be something around 110V AC.

Sorry, there is absolutly no circuit plan for these boards available... at least i have never seen something like that, just the normal service manual, which contains no circuit description.

The only thing i can say: replace all transistors on this cooler.

You have checked the coil and the signals with an oszilloscope? If one halfwave is missing, the voltage on the output is decreasing to 30-50V... exactly what you found.

 

Martin

Franck
Not Ranked
Near Paris
18 Posts
OFFLINE
Gold Member

you can perhaps take a high quality top/bottom pictures of the board to help us to make a back engineering of the schematic :)

I love when a plan comes together

Beogram 4002 / Beocenter 9000 / Beocenter 9500 / RL140 / Beolink 1000 / Beolink 4

MCB
Not Ranked
Denmark
24 Posts
OFFLINE
Bronze Member
MCB replied on Fri, Sep 12 2014 8:58 PM

maybe this will help...

webbda77
Not Ranked
9 Posts
OFFLINE
Bronze Member
webbda77 replied on Sat, Sep 13 2014 12:41 AM

Thanks for the posts - I've got a bit of lead time for the NPN transistors to turn up, but this is all great supporting info.. I'm on the right track hopefully - I'll update how it goes

Weebyx
Top 100 Contributor
Denmark
986 Posts
OFFLINE
Bronze Member
Weebyx replied on Thu, Oct 23 2014 10:51 AM

Hi, did you ever get this working ?

Im having a totally dead voltage(0) on black/brown wires, and I cannot hear any humming from the coil at all, otherwise the remote is working perfektly, just like yours :)

I have checked the 1A250v fuse, and it is fine..

Any great ideas ?

webbda77
Not Ranked
9 Posts
OFFLINE
Bronze Member

Hi,

Sorry to report that I have not had much good luck with this unfortunately - as well as new NPN and PNP transistors, I tried a whole replacement PCB1 board, and it still made no difference.

The fault finding flowchart in the manual recommended both PCB 1 and 2 be replaced for this issue, and I decided to cut my losses where they are and just sourced a fully functional BL7000 - even with the backlight inoperative it's OK as a #2 unit handy elsewhere in the room to adjust volume etc.

There must be a switching function driven by PCB2, but I'm even less sure where to start with that.

 

 

 

 

 

Weebyx
Top 100 Contributor
Denmark
986 Posts
OFFLINE
Bronze Member
Weebyx replied on Mon, Oct 27 2014 10:18 AM

Hi, thanks for your reply, that actually helped me a lot, I have the Service Manual, but did not think that it could be from PCB2/3 the control of the trafo could be located :)

In my case this makes a lot of sence, since I measure 0V at the trafo, so the circuit is not even powering up... I have exchanged PCB2 in my 2 BL7000's, and both processor boards are actually working in my "working BL7000", so the fault could be on PCB3 or 4 also, don't know if the display board is exchanging data with the processor board, and should return "ok" for the processorboard to turn on the backlight..

But, I have a friend at B&O and he has the BL7000 now, he will try to do some measurements on it and see if he can do something :)

I will let you know..

/Weebyx

Weebyx
Top 100 Contributor
Denmark
986 Posts
OFFLINE
Bronze Member
Weebyx replied on Mon, Oct 27 2014 10:24 AM

And..... My friend has just gotten back to me, he has changed TR37 / C15... and now it works like a charm again :)

 

/Weebyx

Weebyx
Top 100 Contributor
Denmark
986 Posts
OFFLINE
Bronze Member
Weebyx replied on Mon, Oct 27 2014 10:32 AM

One more thing ...

Have you tried changing the backup battery on PCB2(processor board) ? Sometimes a low voltage there, can cause side effects..

 

/Weebyx

beophonic
Not Ranked
15 Posts
OFFLINE
Bronze Member

hello weebyx, thanks all here for the great info. im having a challenging time with the same symptoms, where is c15 tr37?

thanks very much!

Weebyx
Top 100 Contributor
Denmark
986 Posts
OFFLINE
Bronze Member

It is the one with the black circle :) I also changed the capasitor C15 (10nF) also in the black circle, but I think that the transistor is the problem if you are having 0v like me...

 

 

/Weebyx

beophonic
Not Ranked
15 Posts
OFFLINE
Bronze Member

fantastic, no wonder i couldn't find it! thanks and thanks to die_boegner. es i have 0v, so will get onto it in the morning!

 

beophonic
Not Ranked
15 Posts
OFFLINE
Bronze Member

thank you very much

how many volts does the c 15 have? i bought 10v
:/
Weebyx
Top 100 Contributor
Denmark
986 Posts
OFFLINE
Bronze Member
Weebyx replied on Sat, Dec 26 2015 2:12 PM

I used 50v in mine, but really don't know what the correct voltage should be..

 

/Weebyx

Page 1 of 2 (24 items) 1 2 Next > | RSS
Beoworld Security Certificate

SSL