Forgot to mention that I also swapped TL431 with a good channel in my previous post. Prior to that I have used external supply and tested TL431 in circuit and it was OK.
Perry, any idea what would be suitable zener diode replacement for Xtant X604. I guess it is small enough and I should use 500mW version. Should I swap both Zeners at the same time (rail+ and rail-)?
Unless they run hot or are out of tolerance, I'd only replace the one that failed. Any 1N5239 should work. In photos, it appears to be 1/2w (as you stated) but confirm by measuring with dial caliper.
I haven't ordered the 9.1V zener yet, but was able to get the part from another project I am currently working on. No changes were noted. The amp still had negative offset in -4.8V to 7.4V range. Power supply was making the most amount of noise when I was near -4.8V. Wondering if output transistors could be culprit in here.
Also I don't know what Q1 transistor is. Need to figure out what Q1 transistor is and whether I could source it on digikey/mouser.
Also I don't know what Q1 transistor is. Need to figure out what Q1 transistor is and whether I could source it on digikey/mouser.
I don't believe it is defective not do I believe the output transistors are defective but I have figured if I am going to place the order might as well get more parts just in case. I have hit the wall with this failure. I need to inspect it once again under the microscope, but there is not much there to inspect.
Q1 D428 seems like 2sd438 and comes in TO-92 package.
Q1 D428 seems like 2sd438 and comes in TO-92 package.