Hey Chris,
I would assume that these questions are not as important as they were three months ago, but....
I have a Janus 5-knob Preamp (and the 1983 plastic-key Mark II it lives in). The PC Board is marked 018017, which is part of the 018019 whole assembly.
For years, I had no power supply to test it, but in the blazing crater that is the RadioShack going-out-of-business-again sale, I bought 20 AA batteries, and the plastic carriers to mount them in. I used the batteries to build a +15V and -15V power supply for the Janus preamp. It works great. (I also tested the preamp at +/-12V, and it works fine at the 20% lower voltage.) The preamp draws less than 75mA with the Vibrato switched on (40mA from the negative supply, 35mA from the positive supply).
So here are the answers from your post from last November:
1.) R14 and R26 are connected to voltage. But it's not mentioned, if it's + or -.
R14 is connected to V+ (forward bias of the BE junction in Q1, and forward current in the LED are hints).
R26 is connected to V-.
2.) Does anybody know how much current which voltage goes through the LEDs (power & vibrato)?
The power LED draws current from the negative supply through R39. Measured voltage drop through the resistor in my unit is 13.41V. If we pretend that this resistor is exactly 1000 Ohms, then the current flowing through the LED would be 13mA.
The vibrato LED has the same 1K Ohm current-limiting resistor, so it will draw the same 13mA when turned on. Remember, the LED is not on 100% of the time, and there is probably one and a half volt dropped across the switching transistor [Vce(sat) on the MPSA14 Darlington].
3.) There is no blocking-cap on U1. I think it's better to add one?
The two op amps in U1 are not in the audio signal path, they are the oscillator and buffer amp for the vibrato. Probably don't want to add any capacitors in the midst of the vibrato oscillator.
4.) C19 says 100uF while C20 says 100pF. Do you think that's a mistake and it both needs to be 100uF? This would make sense to me. I agree, that has got to be an error. My preamp has both of these caps replaced with 22uF electrolytics, and works just fine (but, of course, there is no ripple in my battery power supply).
On my preamp, these caps were replaced thirty years ago as a result of what looks to have been a fire. There are missing traces (mended with jumper wires), and black soot marks on the underside of the board. My preamp has no enclosure, and it would be easy to short out the power connections on that corner of the board.
Sean