Beomaster 6000 volume preset not working

8 replies
TH
Offline
thch
Silver
Posted November 22, 2018 at 22:54 GMT
#2209332

Hi.

There is propably a simple fix, but I haven't been able to find any help in this forum.

Problem: Beomaster 6000 (type 225x), volume v and ^ works. Preset volume using slider goes all the way up when not in zero. (either 12V or -12V across motor unless at zero). Preset value 0 works, value 10, 20, 30, 40, 50, 60 goes all the way to 60 and motor keeps turning (12V on motor).

I have tried the following: All transistors on pcb 6 is OK. Recapped pcb6, resoldered all connectors. Recapped pcb 3, tested volume pot (3R4) 100K ok. Changed pots 6R25, 6R24 and 6R32.

Supply voltage to pcb6 is ok. IC3 is ok.

Preset voltages (measured on cathode 6D8) are all ok (1V to 15V)

Have not changed 6IC5.

When trying to calibrate volume control:

1. volume step 0: Not possible since volume goes all the way up when pressing preset 30. In position 0 voltage on motor is 0V

2. preset volume 0: OK, when preset pot low,  voltage across motor (5TP20 and 5TP21) is 0V

3. v ^¨ volume speed: OK, 6,5V across motor when buttons are pressed

 

What am I missing?

 

Regards Thomas.

TH
Offline
thch
Silver
Posted November 23, 2018 at 20:46 GMT
#2209333

Anyone ?

TH
Offline
thch
Silver
Posted November 23, 2018 at 20:46 GMT
#2209334

Anyone ?

DI
Offline
Dillen
BronzeModeratorFounder
Posted November 24, 2018 at 07:35 GMT
#2209335

Check for cracked solder joints at the volume control board and also at
the connectors along the lower edge (in serviceposition) of the CPU board.

Martin

TH
Offline
thch
Silver
Posted November 26, 2018 at 13:23 GMT
#2209336

I found a "CPU donorboard" from another dead BM6000 and that worked, thanks for guiding me in the right direction.

 

Is it easy to kill the CPU in these machines? The CPU donorboard wasn't working until I changed the CPU (the error was just showing the small 3 dots in the frequency display). I thought that stuff was pretty reliable....

DI
Offline
Dillen
BronzeModeratorFounder
Posted November 26, 2018 at 13:51 GMT
#2209337

It's CMOS - it's always sensitive to static electric discharging.
ALWAYS work in an ESD-safe workplace with correct tools, wrist-strap etc.  - particularly when working with CMOS.

Martin

S(
Offline
sonavor (archived2)
Bronze
Posted November 26, 2018 at 13:54 GMT
#2209338

Changing the board doesn't mean the problem was with the microcomputer IC itself. It just means there is likely a connection problem with that board. Don't discard that old board and microcomputer IC in the trash. People suspect the microcomputer all the time when something doesn't work and it is rarely the case. It is almost always a missing or faulty signal to the microcomputer IC.

-sonavor

TH
Offline
thch
Silver
Posted November 27, 2018 at 11:35 GMT
#2209339

Well, I have tried to place the uP in a working processorboard and only output is the 3 dots on the freq. display. So I guess the uP is dead.

or
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