left/right balance

[christiancarvin]

hello!!!

My ssl4000 recently shown a difference of 0.5dB between left and right.
Is there a way to correct that quickly, or do I have to recalibrate pan of each module?

thanks!!

[walrus]

How are you measuring the difference? Using the Mix out VU meters, or using an external meter.
Is the difference there if you patch the oscillator into the Pre/Post Master fader VCA patch points?

[christiancarvin]

Thanks for your reply!

I'm using VU meters of the desk.
The difference is not there if I patch the oscillo in pre and in post fader vca patch point.

[walrus]

Could still be the 82E26 card. Try swapping the Left and Right cards around and see if the difference moves.
Also, does the difference change with frequency?

[christiancarvin]

I've never entered in the center part of the desk.
Sorry for that newbie question, but what's the procedure to do that correctly?

Thanks!

[walrus]

Has your desk had all its capacitors replaced? As fading caps on the 26 cards can cause a level imbalance.

To lift the centre section first turn of the power to the desk.
Then you remove the 2 screws top and bottom and if you have the lifters, and the threads in the panel are still good, you use the lifters to raise the centre until it locks into its raised position on its rails. However, it is often safer to remove the cover panel under the desk, and push it up from below.
This operation is best carried out by 2 people if you have never done it before, as it is heavy and trapped fingers *will* hurt! 

Can't remember the exact position of the 26 cards, but they are 4 identical cards around the middle-ish.
Once you find the cards and swap the LF with RF you can re-power the desk with the centre raised to check results......

Hopefully Andy will be along soon to confirm or say "No no no, don't do this...."    "try this instead...."

[Showcase]

Could still be the 82E26 card. Try swapping the Left and Right cards around and see if the difference moves.
Also, does the difference change with frequency?

Id try this first aswell, could be a bad bi-cap... just loosen the screews and push it up from under the console until you hear it clicks (hopefully it stays up, the rails can go bad so you might want a freind to help perhaps)

[sintech]

Yeah, agree with Kevin, two people make this job simple.

The 651 must be powered off when moving up and down.

Hopefully the fault will move with one of the 026 cards, and you can leave two covering LF RF, whist recapping the other two.

Found that new caps, just sort any niggles out, and makes for a nice silent noise floor.

[christiancarvin]

Thanks everyone!!!!

I'm going to try that!

[christiancarvin]

The problem stays after exchanging 82E26.
Any other suggestion?

[sintech]

So if you cross patch the Pre VCA from Left to right, the issue moves with the patch?

Next thing to do is reseat the S5 Y cable, either side of the centre section, and also into the bottom of the 651, assuming you have a 4k here.

[waltzingbear]

lets check calibration as well before going furthur, use a meter on the output of the cards, not the VU, to make sure there is a difference or if its the meter calibration.

Alan

[christiancarvin]

I'll do that!

[christiancarvin]

I took time to make a better test, here is what it says on my 4k:

I use an external calibrated VU on Main output.
Oscillator wired in PRE VCA (on the patch): -0.3 dB on left 0 dB on right
Oscillator wired in POST VCA (on the patch): -0.1dB on left 0 dB on right
Oscillator wired in line input of a module: -0.3 dB on left 0 dB on right

The problem stays when after exchanging 82E26.

[walrus]

Those results definitely prove the problem is around the 26 card, either the input caps or VCA circuit.
Have they been re-capped? Are you sure you swapped the LF and RF cards, and not the LB and RB? (Grasping at straws now) 

Try reseating the 27 card and twiddling the Quad compressor controls, and master VCA trim pot.

Does the difference stay the same if you drop the master fader by a few dB, then raise the oscillator level back to match?