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Tuesday, September 10, 2013

Beomaster 8000 Display Issues

Today I looked into the display issue on Beomaster 8000 #4 (see http://beolover.blogspot.com/2013/09/beomaster-8000-first-inspection.html). The initial suspicion that there is something wrong with the communication between the microprocessors and the displays turned out to be wrong...the missing displays segments are just broken, like in most Beomaster 8000s when they come from ebay. I extracted the balance display and inserted it into my display test fixture and biased it with ~1.7V. Only four segments showed up for the party:




























It is interesting to note that there are two 7 segment display decoders (IC1 and IC2 on the processor board (=#9)). IC1 addresses both balance and volume displays, while IC2 drives the frequency and the input displays. Which one of the two displays is on depends on the phase signal, which turns them on alternatingly at a frequency that is imperceptible by the human eye. It follows that the segment drivers are both o.k. if one of the two attached displays is showing a coherent data display (even with some display segments missing). The same is valid for the phase signals. Oh well: On to another display repair session (check out: http://beolover.blogspot.com/2012/09/beomaster-8000-display-repair-hopefully.html). I just ordered the SMD LEDs...for a consistent brightness across all four displays, I will have to do them all.

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