Beomaster 2400 muting always ON

5 replies
BE
Offline
BeoGrad
Bronze
Posted February 4, 2015 at 23:22 GMT
#2201913

Dear Beoworld fellows,

this is my first login and post after more than 10 years - the stuff has been working greatly up until recently when my Beomaster 2400 developed a fault.

All touch commands work function without problems and all lamps are working except the treble one but the fault appeared independently. Namely, one morning I turned it on only to discover that there was no sound coming out. After thorough checkup, I discovered that muting transistors 2TR206 and 2TR207 are switched on (cca. -9V on G) as soon as the unit is powered. Backtracing this fault brought me to 2IC6 where pin 13 is permanently on -12V and I suppose this triggers the muting. All components from there are healthy: 5TR7, IL10, as well as components on PCB3. 

Other useful info:

- all supply voltages are within specs

- muting transistors 2TR306/307 are not shorted to the ground

- output stage is healthy

I hope everyone is doing well and fine here at Beoworld and I am thanking you in advance for your kind advice on how to repair the 2400.

 

Best regards,

Milan

DI
Offline
Dillen
BronzeModeratorFounder
Posted February 6, 2015 at 07:53 GMT
#2201914

Check the lamp inside the LDR casing.
You can measure it from the solder side of the main circuitboard.

Martin

BE
Offline
BeoGrad
Bronze
Posted February 7, 2015 at 11:43 GMT
#2201915

Hello Martin and thanks to your reply. The lamp is OK and the whole volume control works: namely, the IL1FAULT circuit is not active, the volume sensors respond and do not pull volume back to zero.

My question is if -12V on IC6, pin 13 is mute or normal state? Otherwise, is disabling e muting circuit a viable solution?

BE
Offline
BeoGrad
Bronze
Posted February 7, 2015 at 11:44 GMT
#2201916

Hello Martin and thanks to your reply. The lamp is OK and the whole volume control works: namely, the IL1FAULT circuit is not active, the volume sensors respond and do not pull volume back to zero.

My question is if -12V on IC6, pin 13 is mute or normal state? Otherwise, is disabling e muting circuit a viable solution?

DI
Offline
Dillen
BronzeModeratorFounder
Posted February 7, 2015 at 12:20 GMT
#2201917

Pin 13 of IC6 is a lamp output.
I've seen many cases of muting due to wrong wattage lamps fitted to the source indicators.
Note how the indicator lamps links to the muting circuit (TR6 on the volume board), making the lamps a critical part of the circuit.
Check that the lamps are correct (or grab a kit and replace the lot if not already done).

Martin

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