Hello everyone, Well, I've got a problem that's causing me to pull what little hair I have left out. The right side of the mix buss on my Series II went out (not all the way, but severely lacking in level) and I can't seem to figure out why. When I'm mixing through the board and when I run the oscillator through the 2-mix, the right side is way down. Adjusting the right level pot doesn't help at all. When I select one of the tape inputs (CD, iPod, etc.), everything works fine. Here's what I've done so far:
The 2-mix master module checks out fine EXCEPT when I have it feeding the control/studio room modules. Something is pulling current on the right side because the supply voltages are about 2 volts lower on the right side vs. the left. If I lift the end of the resistors that feed the control room module and jump the right side from the 2-mix to feed the left channel down the circuit in the control/studio module, it works and the meter registers the right level. When I connect the left to the right side, I get the same problem on the right; that is, no level on the right. This tells me both sides are working fine up through the 2-mix module and that the problem is definitely downstream on the right channel. Whatever is causing the right side in the 2-mix module to draw more current must be down circuit somewhere. OK, I figured, on to the control room monitor section. The outputs from the 2-mix module feed an IC and the TAPE switches on the control room monitor PCB. The output from the IC feeds goes to the switch bank and also on to the "buffered 2-mix" that feeds the "studio monitor module" and the switch bank for selecting 2-mix, tape 1, 2, 3, 4, and cue. It also feeds the 2-mix meters. My best guess is that something along this signal path is where the problem lies, but I'll be damned if I can locate it. I've replaced all the ICs in the signal path from the 2-mix through to the meters and also found some other suspect things that I fixed, but the problem still persists. I'm going to disconnect the feed to the meters tomorrow to see if the problem goes away. I'm also going to drop the bottom off to check the solder joints on the motherboard molex connectors even though I replaced those a few years ago. This problem definitely has the feel of some extra resistance somewhere that's pulling the signal down. I know I'm rambling a bit, but I've been on this all day and I guess I'm a bit frustrated. If anyone has and ideas, fire away! I wish I could attach the schematics. Maybe I'll scan them and host them somewhere tomorrow if anyone wants to have a look. Of course, this happens right before my busiest week of recording audition CDs for the music students at the school where I work. Since many of them end up in places like Julliard, Manhattan School of Music, Colburn, and New England Conservatory, etc., the stakes are high and I need to get this fixed or figure out a plan B pronto. Thanks, -- Don
