Author Topic: issues with vca group 6 and 8 >>> SOLVED <<<  (Read 357 times)

christiancarvin

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issues with vca group 6 and 8 >>> SOLVED <<<
« on: June 01, 2021, 02:25:04 PM »
hello every one!
My VCA group 6 and 8 doesn't work. When the faders are way down, the sound still goes through and Cut doesn't mute.
 Is it possible to have your help on it?

thanks!
« Last Edit: June 18, 2021, 02:31:57 PM by christiancarvin »

mg73

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Re: issues with vca group 6 and 8
« Reply #1 on: June 01, 2021, 09:26:06 PM »
Does SOLO work?

have you checked you  cables(flat ones) between console and computer and that they are connected properly etc?

christiancarvin

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Re: issues with vca group 6 and 8
« Reply #2 on: June 02, 2021, 09:45:16 AM »
Thanks for your answer :)

I've plugged and unplugged the flat cables connected to the 80E20 and exchange flat cables on 82E38 between VCA group faders: no changes.
Weird fact: every solo button of the VCA group section solo the VCA group faders 6 and 8.

 
« Last Edit: June 02, 2021, 04:19:46 PM by christiancarvin »

christiancarvin

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Re: issues with vca group 6 and 8
« Reply #3 on: June 03, 2021, 08:31:58 AM »
I have tested capacitors and diodes on 80E20 (VCA faders and mutes card) and they are ok...

horizonsound

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Re: issues with vca group 6 and 8
« Reply #4 on: June 03, 2021, 09:03:22 AM »
Check the fusing resistors on the 82E20 card which would be R22, R60 (Ch 6) and R24, R62 (Ch8).
I've had these blow out, along with the associated transistors, T15, T27, and T17, T28.

This part of the circuit controls the voltage to the VCA bus.

If you have a computer, run !TES and see if the computer responds to the VCA faders under the Input test page.

Anthony.

christiancarvin

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Re: issues with vca group 6 and 8
« Reply #5 on: June 03, 2021, 03:33:04 PM »
Thanks Anthony,

I've checked R22 and R24 and they are ok. I can't use the computer.
As you can see on the picture, there are no T15, T27, T17, T28, R60, R24... Did I miss something?







horizonsound

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Re: issues with vca group 6 and 8
« Reply #6 on: June 03, 2021, 10:53:35 PM »
Ah OK, older version E20 card.

Might be the op amps associated with those channels. Channel 6 & 8 share the same chip.
If you don't have spare, switch T2, T4 and T6 with T1, T3 and T5 respectively, and see if the issues follows the chips.
Sometimes reseating the chips will fix the issue.

I suppose you don't have an extender card?

Anthony.

christiancarvin

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Re: issues with vca group 6 and 8
« Reply #7 on: June 04, 2021, 06:22:04 AM »
I've exchanged the opamps, the problem is still here. I don't have extender card for the central section. I also exchanged RA  and RB and checked R1,R2,R3,R4,R5,R6,R7,R8...still the same!

It's a tough one!
« Last Edit: June 04, 2021, 07:04:10 AM by christiancarvin »

horizonsound

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Re: issues with vca group 6 and 8
« Reply #8 on: June 04, 2021, 09:19:36 AM »
Should not be too difficult, the circuit is very simple.

0v = fader at maximum, and +10v = "CUT". You are not seeing any control voltages going through fader 6 & 8.

Can you measure to see if you are getting a constant 5v on pin 2 of your 20 way ribbon cable to the fader.
Pin 1 should vary between 0-5v as you move the fader with 0v at maximum, and +5v at fader minimum.

Anthony.

christiancarvin

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Re: issues with vca group 6 and 8
« Reply #9 on: June 04, 2021, 10:47:16 AM »
Thanks for your reply Anthony,

I've checked it: That's exactly 0 to 5V on pin 1 as I move the fader, and 5V constant on pin 2 on faders 6 and 8.
It is very tricky

« Last Edit: June 04, 2021, 01:24:23 PM by christiancarvin »

christiancarvin

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Re: issues with vca group 6 and 8
« Reply #10 on: June 10, 2021, 07:28:53 AM »
Please, would you explain me how does work the vca in that part of the desk? I've read things like "gain of the amplifier then depends on the light falling on the LDR" but here I can't see any led diodes. Thanks :)

christiancarvin

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Re: issues with vca group 6 and 8
« Reply #11 on: June 16, 2021, 09:05:51 PM »
After a lot of tests made on the card, I can say that it is ok. The issue come from an other place...It surely has to do with 681E part: the access here is very difficult.
« Last Edit: June 17, 2021, 05:38:21 AM by christiancarvin »

christiancarvin

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Re: issues with vca group 6 and 8
« Reply #12 on: June 17, 2021, 08:01:43 AM »
I've got no computer connected, instead there are jumpers under the patch bay that shorten the circuit. One of them: the one called VCA 1-8 was half connected, it is responsible for sure. But  weird thing: when I completly connect it, sound is no longer coming to LF/RF.
New issue!
« Last Edit: June 17, 2021, 08:03:16 AM by christiancarvin »