sonicmook56
Well-known member
Well, it's been awhile since I've posted here!
Can anyone ID this VCA? It's from a fader in my Sony badged MCI JH 636 built in 1985. Story below the photos....
Long story short, I picked up an MCI 600 series console last year which I've been enjoying mixing on. Aside from replacing a few switches and switch caps, I haven't really done anything to it except clean it up and wire it into my studio.
The major thing that's been off since I got it is the level to the mix bus from the VCA fader. It's way off! I've been getting around this the past year by putting everything in a group, then goosing the group master up.
Using a 1K tone at +4 (1.28VAC) to a line input, panned all the way left and the large fader at "0", I get around -10 on the VU meters. Switching the VCA out of circuit to the rotary channel fader set to "0", I get "0" on the VU meter, which is what I would expect. Please see short video for more explanation.
https://youtu.be/cxCobGfRk60
It seems that the overall level of the VCA system is off. I've calibrated a few things, checked all the rails (twice) but no changes were observed. I should note that it doesn't matter if the automation PSU is switched on, or off... It behaves the same.
I'm at the point now where I must assume that someone changed the original VCAs to a type with a different mv/dB sensitivity., but failed to change the surrounding support circuitry. Crusty flux around the VCA pins, but nowhere else indicate this as well.
So, in hopes to find the correct resistor values, I need to ID these VCAs. I don't think they are the THAT variety, but maybe they are:
202X
202XT?
I really have no idea!
Can anyone ID this VCA? It's from a fader in my Sony badged MCI JH 636 built in 1985. Story below the photos....
Long story short, I picked up an MCI 600 series console last year which I've been enjoying mixing on. Aside from replacing a few switches and switch caps, I haven't really done anything to it except clean it up and wire it into my studio.
The major thing that's been off since I got it is the level to the mix bus from the VCA fader. It's way off! I've been getting around this the past year by putting everything in a group, then goosing the group master up.
Using a 1K tone at +4 (1.28VAC) to a line input, panned all the way left and the large fader at "0", I get around -10 on the VU meters. Switching the VCA out of circuit to the rotary channel fader set to "0", I get "0" on the VU meter, which is what I would expect. Please see short video for more explanation.
https://youtu.be/cxCobGfRk60
It seems that the overall level of the VCA system is off. I've calibrated a few things, checked all the rails (twice) but no changes were observed. I should note that it doesn't matter if the automation PSU is switched on, or off... It behaves the same.
I'm at the point now where I must assume that someone changed the original VCAs to a type with a different mv/dB sensitivity., but failed to change the surrounding support circuitry. Crusty flux around the VCA pins, but nowhere else indicate this as well.
So, in hopes to find the correct resistor values, I need to ID these VCAs. I don't think they are the THAT variety, but maybe they are:
202X
202XT?
I really have no idea!