How to calibrate console?

[jdurango]

Does anyone here know the process to calibrate a Series 40? I'm getting input levels all over the place, not only audibly, but through not matching up on meters either. There are cal pots on the mic/line/mon/track pan card, VCA's and output meters labeled on schems as follows (schems and pics in Drive link @ bottom of post):

MIC/LINE & MON/TRK PAN PCB
    - R5 50K LO FREQ CMRR TRIM
    - R9 100 HI GAIN CMRR TRIM
    - R24 1K LO GAIN CMRR TRIM
    - R12 50K DE-THUMP TRIM

VCA
Turns out I don't have schems for this, just an assembly drawing that is only labeled
R15, R31 and R17, all 50k. See pics @ Drive link @ bottom of post.

VCA ADD-ON CARD
Got nothing for this one. No schems or drawings. See pics at Drive link @ bottom of post.

METER BRIDGE/OUTPUT CARD
- R5 "0" CAL
- R4 TK CAL
- R6 AVG. CAL
- R2 PK. CAL
- R1 ANA. LEVEL

I've checked install notes, no help there. Don't have a manual. I could probably figure out the output meter/output, but obviously if everything before it in the signal chain is out of cal, that doesn't help much. The VCA's and mic/line card are my main concerns. Any help advice is greatly appreciated! Thanks fellas!

LINK TO PICS AND SCHEMS: https://drive.google.com/drive/folders/1CKDAgrPaWcHgCOTOgpVMh8lrjwsj1dpM?usp=sharing

 

[pucho812]

series 40 by who?

 

[iampoor1]

Those VCA cards will sometimes throw a fit when the cps get leaky. I worked on a Sound Worskshop desk with wonky VCA output levels and changing out the aps on the VCA cards fixed the problem.  I believe they were around -10db from the proper working channels

 

[ruffrecords]

Does is have channel inserts or direct outs? If it does then the first job is to check channel gain.

Cheers

Ian

 

[jdurango]

Hey guys. Yep sorry forgot to mention it's a Sound Workshop Series 40. And yeah, I'd love to bypass VCA's. Tried doing his with some Alps pots, but they wouldn't cutoff signal completely at bottom of fader travel (about 100mvpp leak with about 7vpp at full blast) so I ditched that idea (maybe 100mvpp is acceptable?) or I could add some kind of special diode or circuit to completely cut off anything below 150mv?

Anyway, yeah VCA's in this thing are a PITA!

 

[synthiaks]

What Iampoor1 is trying to tell you is that it might be worth recapping the VCA-cards if not already done.

 

[synthiaks]

Tried doing his with some Alps pots, but they wouldn't cutoff signal completely at bottom of fader travel (about 100mvpp leak with about 7vpp at full blast) so I ditched that idea (maybe 100mvpp is acceptable?) or I could add some kind of special diode or circuit to completely cut off anything below 150mv?

Anyway, yeah VCA's in this thing are a PITA!

Also,

We just had this discussion a couple of weeks ago here with you.:

https://groupdiy.com/index.php?topic=74412.0

the solution was faders with a switch. So when you are fully down you cut the Audio path. And it still is

S

 

[jdurango]

What Iampoor1 is trying to tell you is that it might be worth recapping the VCA-cards if not already done.

Whole thing has been recapped last month.

 

[jdurango]

Does is have channel inserts or direct outs? If it does then the first job is to check channel gain.

Cheers

Ian

Hey Ian, has both balanced inserts and seperate direct outs. Inserts are of course normalled to themselves, direct outs are normalled to AD in, bus outs are normalled to tape. I don't have the $ right now to buy a bunch of super high end faders....not sure why these Alps won't fully attenuate the signal when any cheap pot should do the job just fine. Maybe there are a few bad ones in the bunch or they need cleaning or something. I'll try to get them working. If these won't work, I'll probably have to stick with the VCA's until I run across a deal on some P&G or TKD's.

 

[ruffrecords]

Hey Ian, has both balanced inserts and seperate direct outs. Inserts are of course normalled to themselves, direct outs are normalled to AD in, bus outs are normalled to tape. I don't have the $ right now to buy a bunch of super high end faders....not sure why these Alps won't fully attenuate the signal when any cheap pot should do the job just fine. Maybe there are a few bad ones in the bunch or they need cleaning or something. I'll try to get them working. If these won't work, I'll probably have to stick with the VCA's until I run across a deal on some P&G or TKD's.

Second question first. Cheap pots won't do the job. A typical 10K pot might have an off resistance  of 10 ohms - that means the off attenuation is only 60dB. The better ALPS faders are much better. You also need to watch how you physically wire them because any resistance in the analog 0V in the return leg will affect the off attenuation.

With direct outs you should be able to calibrate each channel. Feed a known signal level in, set the mic gain to the setting that should give 0dBu out and measure at the direct or insert point (assuming they are meant to be at the same level). Adjust the gain trim to get 0dBu out. You can probably leave the CMRR trim controls as they are.

Cheers

ian