ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hello,
I Have a new beomaster 2400-2 with trouble. Audio signal is comming in the input of TR206 and TR306 but not at the output of these transistors. Muting trouble. I can swap input (phono, tape, fm ....).
All bulbs are OK except : bass bulb, treble bulb, and the two green bulbs near standby led.
If I inject signal directly in the input power amp ( R201 and R301 ) it is OK, I have sound in the output speaker.
The trouble is in a muting circuitery. Deads bulbs can explain muting trouble ?
It is difficult to understand muting shematic.
Thanks for your Help.
Franc
Welcome to Beoworld!
Yes, bad and/or wrong wattage front panel bulbs can cause strange behavior in this Beomaster but in this case it's mostlikely a defect bulb inside the LDR casíng.
Martin
Hello Martin,
Thanks for answer.
I can find Bulbs LDR casíng in the schematic, where are they.
Thes bulbs can affect muting circuitery ?
Valédian
The LDR casing is a small metal casing on the main circuit board, it's about 2x2cm containing - well... LDRs.Four LDRs in total.They sit around a small bulb as scouts around a camp fire, all closed from ambient light, performing the task ofsetting the volume based on the amount of light from the bulb - which again is controlled by the circuit under the volume sensorpads.The more light - the quieter the Beomaster plays. So when the lamp burns, the Beomaster would thengo to full volume if it hadn't been for the muting circuit, sensing the current draw of the bulb, muting (or in most cases bringing theBeomaster to a very faint whisper), when the bulb burns.
Thanks for answer, very precise.
I dont know there is a LDR trouble because I can use volume control, and I can see good audio signal on C217 and C317. It is just the electronic command of TR206 and TR306 who stop the audio signal on Fet Transistor, I think it is a muting circuitery have a trouble but I can find where is a default. The Amp section is goog because if I inject audio signal on output balance potentiometers the sound on the speakers are OK.
Thanks,
Beomaster 1900 and 2400 is very sensitive to correct wattage frontpanel lamps.Wrong frontpanel lamps can cause strange behavior, and it can actually activate the muting.I know it sounds strange, but the circuits are related, allowing the Beomaster to mute briefly when switching sources.I seem to remember that TR6 on the volume board is handling this.If its silent on all sources, check the power supply voltages - and indeed TR6 itself.