On Sat, 5 May 2018 15:10:00 +0200 Edward Bartolo <edb...@gmail.com> wrote:
> [ Lately, I am trying to understand how in the whole universe, all > collectors of 16 ouput transistors (2SC5200 & 2SA1943) in an amplifier > are earthed! Yes, earthed! Why not the 0 volt rail of the power > supply?! ] If your amp is anything like most of the amps I repaired at Pacific Stereo, George Meyer TV and Steve's Stereo Repair, the emitters of these transistors connect to the free-floating speaker output line (which *might* be what you meant by "0 volt rail") via high wattage resistors in the neighborhood of 0.1 to 0.5 ohms. The resistor is there for stability. The transistor collectors are connected to the unregulated V+ (2SC5200) or V- (2SA1943). Both are driven at their base by the emitter outputs of the driver transistors. If, by "earthed" you mean the collectors "grounded", as in attached to the chassis or something directly wired to the chassis, that would be a unique configuration for output transistors: I never saw it in 5 years of consumer electronic repair. I'd suggest you obtain a schematic of the amp involved. I think you'll find the collectors connected to the + and - supply rails, not to ground. SteveT _______________________________________________ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
