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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Thanks.
