Beomaster 8000 Restoration: Output Stages

Beomaster 8000: Right output run with external power supplies for testing.

The restoration of the output amplifiers of the Beomaster 8000 is essential for reliable operation. Practically all 8000s have corroded quiescent current trimmers in both channels by now, i.e. they need to be replaced. It is recommended to replace them with encapsulated 12-turn precision potentiometers. This results in excellent temperature stability of the adjusted setting, and also essentially stops drift of the adjustment over time. An indication of trimmer failure is overheating and/or output transistor failure.
Please, visit these blog entries at http://beolover.blogspot.com for detailed accounts of this restoration procedure:

• http://beolover.blogspot.com/2011/09/output-stages-testrecap.html (this post shows some detail about the trimmer replacement)
  
• http://beolover.blogspot.com/2012/08/beomaster-8000-left-output-stage-rebuild.html
  
• http://beolover.blogspot.com/2012/06/beomaster-8000-rebuilding-power-amps.html

These blog entries discuss a case where output transistors needed to be replaced in one channel:

• http://beolover.blogspot.com/2013/09/beomaster-8000-output-transistor.html
  
• These two posts reports a case, where only one transistor died in the right output:
  
• http://beolover.blogspot.com/2014/02/beomaster-8000-interesting-output.html
  
• http://beolover.blogspot.com/2014/03/beomaster-8000-right-output-working.html
  

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