[Madskp]

My BM5500 has developed a fault when choosing sources.

If I select CD, TAPE or phono it will flicker between sources in the display and a relay is clicking continuesly.

If I select radio this doesn’t happen

The last thing it was used for was in a test scenario with a Beolink converter connected to the TAPE2/AUX input if this can give any hint as to what could be the reason for this behaviour.

Any ideas where to start looking?

Thanks in advance

[Die_Bogener]

There is a LED driver chip MM5450 on the display board. If there is a problem with overload of a segment… the chip has internal led driver resistors… it will have problems to activate the defekt segment causing a power failure of the display/cpu… that’s the flicker.

Try the amp without speakers to activate from 0 to 64 to check all these segments. Usually there will be a “8” problem… and a problem with the source led.

It can be the chip or the power supply itself.

Replacing the chip is very skilled work and the chip is hard to get.

Usually some caps in the power supply are the cause…

[Madskp]

Die_Bogener wrote:

Try the amp without speakers to activate from 0 to 64 to check all these segments. Usually there will be a “8” problem… and a problem with the source led.

Thanks for the input, I will try to look into that.

But just to clarify it is not the seven segment displays that flickers, but the names of the sources that are rapidly changing, each time followed by a relay click. Don’t know if that affects how you see the problem?

 

[Die_Bogener]

7-segment and Led’s for the source are done with the same chip… and the relais.

[Madskp]

Ok thank you, then I will take a look around there when I ger it open

[Madskp]

Had some time look further into it today.

Die_Bogener wrote:

Try the amp without speakers to activate from 0 to 64 to check all these segments. Usually there will be a “8” problem… and a problem with the source led.

The 7 segment display can show 88 i both display units.

Die_Bogener wrote:

It can be the chip or the power supply itself.

Power measured at pin 2 and 5 in connector p11 on the front panel PCB is 5,18V steady even with the flickering and relay clicking

About the relay clicking, now that I have the BM5500 open I can see that it is the relay behind the plug PCB that is clicking rapidly

But I noticed that the relay on the PSU board (betwen the transformer and the large caps) is also clicking once in awhile if that is an indicator for something.

Die_Bogener wrote:

Usually some caps in the power supply are the cause…

Which caps would that be if I should try to test some of them?

Thanks in advance

 

 

[Madskp]

Die_Bogener wrote:

Usually some caps in the power supply are the cause…

Is it those orange 10 uf caps here, C8, C9, C14?

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