G+ Buss Compressor Calibration?

[ciaopatsy]

Hi all, I've had my G+ for two years now and so far its been difficult to get the buss compressor to stay around the "magic" -4db of gain reduction when mixing. Even with the buss comp's threshold at +15 (attack 30, release auto) it still pulls closer to -8db of reduction on the average mix. I don't think I'm hitting my desk any harder than the next guy, and when I use outboard buss compressors in place of the SSL comp they behave normally. Is there anyway to calibrate the desks buss compressor? I've seen some calibration documents for individual channels but they didn't have  any info about the center section. Thanks!

[walrus]

Long time since I've had eyes on the actual cards, but looking at the schematics for the 26/27 cards
there doesn't seem to be any trimmer resistors.

[horizonsound]

On a G series 6082027ENP, you have a few adjustments, though there is no procedure available that I know of.

They typically control the overall VCA level to the compressor, but also the level (post master fader), going to the computer.

See attached.

[ciaopatsy]

I saw those trimmers while I was poking around, thank you for confirming! I attached what I found in the service manual.

Would I measure voltage at the comp send pad 19 after R50 and at pad 15 for VCA voltage? I have the center section extenders so I'll be able to power the card power and take measurements.

[walrus]

Schematic I have is from 1986 and was for the E series.
They've changed it a bit since then! 

[Dave Dicson]

Newer versions have TO-220 voltage transistors. I have both types.