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
I took a closer look at the standby power consumption of my Beomaster3500 (technically identical to the Beomaster4500). It is about 9W in standby. This calls for the use of a switchable power strip. However, when switching on and off via a switchable power strip, a short crackling sound is noticeable in the loudspeaker (Beovox CX100) and a rattling of the standby and mute relays. Well, the EU's eco-design directive (standby < 1.0 or 0.5 W) came in 2005 and these Beomasters were developed long before that. But I'm surprised if this cracking sounds wouldn't have bothered users in the year the BM3500/4500 was released, it's bad for the speakers after all.So is the behaviour an ageing defect? Is there anyone who remembers how this was with a new system? Was there a software update or service note about this?What I have found so far: In all the BM3500/4500s I've examined, both standby relays and mute relay pull in briefly when plugged into the circuit and drop back as the microprocessor ramps up, causing the speaker crackle. These relays are normally open contacts in the Beomaster 3500/4500 (unlike other B&O systems). If you unplug the system in Standby, the relays try to pull up again before the power supply in the unit collapses. This is probably caused by the pull-up resistors at the output of IC 8155-2. Can someone explain their function to me? I have found no indication in the data sheet that these pins are open collector. Nor about the maximum current these I/O-pins can switch to HIGH or LOW on Output (however, the wiring of the mute relay driver transistor in the Beomaster suggests more than 5mA). Has anyone ever investigated this?
b.r. Franky