tusntuk2
Active Member
Greetings fellow Ak'ers! This puzzle has me stumped - any good puzzle solvers out there wanna try it? I have rebuilt a Kenwood KA-3500 amp with a full recap, many transistors, resistors and diodes, and new Bournes trimmers, too. This is my 12th recap of this model, but I'm stumped. The Left Bias sets easily, but the Right Bias stays static at .3mV. The amp plays.
The Right outputs show .3mV across the emitters, and no turning of the trimmer changes that. After that, I replaced every transistor on this side of the amp (except the outputs) , testing between changes along the way, to no avail. I have taken voltage measurements throughout the right side and compared them to the left. While most figures are different, they are never unreasonable, and they compare pretty favorably to each other. I get to the Right Trimmer and the wiper voltage reads 348 mv, compared to the Left Trimmer wiper voltage of .450 V, (a curiousity of my meter?). The emitter measurements still show .3mv on the Right outputs, and set at 40 mV on the Left. I have checked resistors, double and triple checked every replaced electrolytic, every replaced transistor and diode, every solder joint. The problem has persisted, so I'm missing something. Have you got any ideas?
Any thoughts and help are, as always, greatly appreciated! Something is hiding in there somewhere..
The Right outputs show .3mV across the emitters, and no turning of the trimmer changes that. After that, I replaced every transistor on this side of the amp (except the outputs) , testing between changes along the way, to no avail. I have taken voltage measurements throughout the right side and compared them to the left. While most figures are different, they are never unreasonable, and they compare pretty favorably to each other. I get to the Right Trimmer and the wiper voltage reads 348 mv, compared to the Left Trimmer wiper voltage of .450 V, (a curiousity of my meter?). The emitter measurements still show .3mv on the Right outputs, and set at 40 mV on the Left. I have checked resistors, double and triple checked every replaced electrolytic, every replaced transistor and diode, every solder joint. The problem has persisted, so I'm missing something. Have you got any ideas?
Any thoughts and help are, as always, greatly appreciated! Something is hiding in there somewhere..