The Talkback circuitry is on the Studio Monitor Module (has it's own
schematic). The dim signal (low or ground) comes from there over to
the Control Room Module via jumper
Greg Norman "∆ B12" Look for a short to ground somewhere, also in
the slate switching. Dummy check to see if the slate button isn't
pressed.
Electrical Audio Recording
773.539.2555
www.electrical.com
On Oct 14, 2010, at 1:51 PM, jerry macdonald wrote:
Hello list,
A client of mine has a Series II that has latched the talkback
circuit and won't let go. He had loosened the master section to
wiggle the speaker output molex connector (with solid core wire) as
he was getting some intermittent crackle in the speakers,
apparently did this with the board live but the control room
monitor pot turned down, and while sliding the section back into
place saw all the meters bounce and light up all the peak lights
for a moment. On this Series II, the master section is on the right
and isn't on pins, just molex connectors, so I think he thought
he'd be safe doing this with the board live. Board is working fine
otherwise, supply voltages all read normal.
Except, now the talkback light is on and the speakers are dimmed. I
had 90 minutes last night to check things: The switch works and the
related transistor below it is passing voltage as it should (when
switch is brought to ground transistor passes voltage) but I can't
figure out where the dimming logic is. I have schematics that don't
have any mention of talkback logic, only of talkback mic pre. The
other thing I can't resolve is that the two schematics for the
master section "Control Room Monitor" and "2-Mix Master Module" are
making reference to 5 ICs each on both boards; The actual 2-Mix
only has 3 ICs unless I am really missing something here, which is
possible as I didn't have enough time to disassemble the two boards
from the master section. It seems possible that I have incomplete
or incorrect schematics. They are numbered schematics: Control Room
drawing number 8111201 drawn by IR and 2-Mix drawing number
8111081also drawn by IR. The board serial number is 8202052
(possibly 8202502 or 82020502) so if the serial number and drawing
number are formatted yy/mm/xxxx I would think I'm pretty close.
Any ideas? I've got them back up and running by patching the two
mix outputs to the power amp and telling them to turn it up and
down at the amp. I'll be heading back there on Saturday, and of
course, they're busy right now so any down time is bad.
Thanks
-jerry
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