im trying to rebuild my racked MCI gears, and i decided to design my own PCB too. so far it seems i have a 3 Band EQ and an oscillator.. 
MID1 (Boost mode) oscillates above the 2nd gain setting, and freq lets me play it like a synth.. Gain also changes the osc. freq. it has a huge gain at the fist Gain step (instead of +2dB)
bad 2002? tried another 2002 in there, didnt help.
bad capacitors / cap. values?
in the schemo i see C1403 = 15p, but on the original MCI board i had 150p (ive put that cap in my board as C1403) another version of the schematic shows 47p. i tried all, but they didnt help the oscillation.
the rest seem to work so far, but its just a quick 1st test..
running from +/-24V, i get +/-13.3V on the 5534's. should i run it from higher voltage, or change resistors to get 17.5V-ish?
with a THAT 1206 / 1646 i/o stage i get +6dB gain if all 4 Band Gains are at unity. is this OK so far, or it should be unity? (THAT i/o is unity gain)
this circuit is only the 1300 / 1400 / 1500 stages, without the Chan ACN (1600s).
probably not the brightest idea, but i swapped the MID1 and MID2 grayhills (incl. their resistors) - still osciallting. so i think the problem is on the PCB somewhere
do R1416 and R1417 have to be 1W?
https://www.screencast.com/t/TpIINkPYovb
thanks!
MID1 (Boost mode) oscillates above the 2nd gain setting, and freq lets me play it like a synth.. Gain also changes the osc. freq. it has a huge gain at the fist Gain step (instead of +2dB)
bad 2002? tried another 2002 in there, didnt help.
bad capacitors / cap. values?
in the schemo i see C1403 = 15p, but on the original MCI board i had 150p (ive put that cap in my board as C1403) another version of the schematic shows 47p. i tried all, but they didnt help the oscillation.
the rest seem to work so far, but its just a quick 1st test..
running from +/-24V, i get +/-13.3V on the 5534's. should i run it from higher voltage, or change resistors to get 17.5V-ish?
with a THAT 1206 / 1646 i/o stage i get +6dB gain if all 4 Band Gains are at unity. is this OK so far, or it should be unity? (THAT i/o is unity gain)
this circuit is only the 1300 / 1400 / 1500 stages, without the Chan ACN (1600s).
probably not the brightest idea, but i swapped the MID1 and MID2 grayhills (incl. their resistors) - still osciallting. so i think the problem is on the PCB somewhere
do R1416 and R1417 have to be 1W?
https://www.screencast.com/t/TpIINkPYovb
thanks!
