Tech discussion > 4K,6K,8K Series

Master imbalance SSL 4000E """>>>SOLVED<<<"""

(1/4) > >>

oyanliz:
Hi all,

I need a hand with a problem we have with our 24 channel 4000E console. I have read all the threads regarding to this issue but I´m still not able to fix or locate the problem. I get this from PRE VCA and POST VCA:

- PRE VCA: 0db LEFT <-->  0db RIGHT
- POST VCA: 0db LEFT <-->  -2db RIGHT

All the strips and the master section have been recapped few months ago and the console has the computer and automation removed. We bought the console 2 months ago, so we are discovering issues like this while we are Knowing the console.

Does mean 82E26 cards are ok if PRE VCA signal is fully balanced? Is it a problem caused by 82E27 card? How can I locate the problem? Any suggestion?

Thanks in advance.

Best regards.

Oihan

sintech:
The best way to trouble shoot this is with a pair of patch leads.

Patch from the Pre VCA (summing output) into the Post VCA Input, over patching the Master fader. Then cross patch Left to Right.

If it makes no difference, then the issue is the 25 card.

If it does make a difference and the issue swaps Left to right, then it's the 26 card.

Also, it could be a dirty patch point

oyanliz:
Thanks for the answer "sintech". I have been testing different options and I am still lost with this.

I have tried several connections, included "sintech" posted connection, I have taken pictures and I would be very gratefull if someone could show the way for fixing this deviation of the master ooutput.

This is what I get:

- PRE VCA out-> (works perfect) 0db left/0db right
- PRE VCA to POST VCA input-> 0db left/-5db right
- PRE VCA to POST VCA input swap-> (still the same issue) 0db left/-5db right
- POST VCA out-> -2db left/0db right
- POST VCA out swap-> 0db left/-2db right

I'm not sure if card 026 and 025, both are the problem or ... When I swap Post VCA outs the imbalance also gets swapped, but swapping Post VCA inputs the imbalance keeps, does not swap, so ...

Maybe the photos could help better understunding ...

waltzingbear:
the pictures don't really help, because we don't know what you are measuring.

Where is the digital meter hooked up? On the output in all cases? other points? not clear.

for instance: in the pre vca photo there are two patch cords, are they to the meter? or what?

I would suggest you start with the oscillator out and use one patch cord and never change the oscillator level. First feed the Master Return and take the readings of Lf and then Rf (you might as well do all four channels, its time to fix the board). Are they the same? if not, find and repair the problem.

Then feed the post VCA return points keeping the metering on the output. Are the levels still balanced or not? Find and correct any problems.

Continue back toward the buss where it appears all is good as I understand your test setup.

I suspect there is a dropped (broken) leg on a line and someone has tried to adjust the problem out in the past. Making it a little odd to understand.   (remember that dropping a line in a balanced system will lower the level 6db in the theoretical case)

Cheers
Alan

oyanliz:
Thanks for your answer Alan, you are right, after reading your post I have realized that the info and photos I posted are not enought clear, so...

I will try explaining what I did:

I have used the signal generator of Pro Tools and I have sent the signal throught to one mono channel. I never have changed the output gain of the Signal generator and did not touch the mono channel neither. I used the same patch cords all the time, same brand, same long.

I have two 026 cards instead of four, so I can use only LF and RF.

Regarding to the photos:

- Pre VCA.jpg-> Directly wired from Pre VCA out to 1-2 line inputs of my converter (Works perfect)
- Pre VCA to Post VCA input.jpg-> Wired from Pre VCA out to Post VCA input and from LF/RF to 1-2 line inputs of my converter
- Pre VCA to Post VCA input Swap.jpg-> Wired from Pre VCA out to Post VCA input (but Pre VCA outs exchanged L<->R) and from LF/RF to 1-2 line inputs of my converter
- Post VCA out.jpg-> Directly wired from Post VCA out to 1-2 line inputs of my converter
- Post VCA out Swap.jpg-> Directly wired from Post VCA out (but Pre VCA outs exchanged L<->R) to 1-2 line inputs of my converter

I will try doing the same tests with one bantam cord (instead of two) and I will remove the 025 card and put it back again, just in case.

Thanks once more for answering.

Oihan

Navigation

[0] Message Index

[#] Next page