Fighting with VCA cards again ---SOLVED---

[oyanliz]

Hi all,

I am back with the VCAs again. I fixed a lot of small things today, but some VCA cards are giving some headache again. I was going to start calibrating all the channels, but I can not do that before fix the VCA issues. I have used all the tricks I learned the last years, but I feel I have not learned enought about VCAs.

I have 3 VCA cards (82E13) not responding to VCA to meters and I am measuring around 2dbu with my NTI ML1 device in Group Output (console record status, FLIP and DIRECT pressed). I have measured different pins in one of those VCA card edge:

PIN 25= -4,93v (fader down) -0,5v (fader on 0) and 0v (fader up)
PIN 35= 4.94v
PIN 29= -18,12v
PIN 30= 18,14v
PIN 23= 12,26v

Then I have 2 VCA cards not working fine, noise, low signal... but they respond well on VCA to meter.

And another curious one, this channel is working fine with the extender in the first bucket. But when I place in his slot (it is channel 22), VCA to meters is not working.

I was reading all the old posts regarding to VCAs and I think I would start cleaning as best as I can all the oxidation of component legs (there is not much but...).

All the VCAs were recapped adn rechiped the last year.

Thanks in advance.

Oihan

[oyanliz]

I have been cleaning and replacing all componnents afected by the leaking of old orange capacitors (replaced last year), replacing diodes, transistors... also swappimg the Gold cans (202c vca)... But I still 4 faulty VCA cards (82E13).

On 3 of them, VCA to meter is not responding, the VU meter changes to vca mode but does not respond to the fader (vu gets down), Those VCA cards have around 10bdu less signal. When replaced by a good VCA card (82E13), everything works fine in the channel strip, so the issue it is not in the logic card or so... I have been checking everything. D1, D2, D3, D11, D21 and D22 diodes and RV15, RV16, T4 and T5 transistors have been replaced in one of those cards (and many of them in the others). I replaced 3.3uF film capaciotrs and swap the 202C can from another card.

Then I have one VCA card (82E13), working fine, sounding good and VCA to meter responding well. But the overload led is on all the time. All diodes from D12 to D20 have been replaced and the value readings of resistors from R53 to R59 seem are fine. When the card is tested in any other channel, the issue moves with it.

I would appreciate any help,

Thanks in advance.

Regards.

Oihan

[horizonsound]

Hi Oihan,

Check traces on the top of the board. I had a number of cards with damaged traces from leaking orange caps.
On the 013 VCA card, a typical failure was also R45 (2.7kohm), which on the older boards had two caps right above it.
4 boards failed where this resistor had disintegrated from the leaking cap.

On the 02 EQ cards, around four of these had damage to the power rails which are on the top layer of the board.

Anthony.

[oyanliz]

I have checked the surround area of R45 in all cards. They are clean (I have attached photos) and top side tracks are well, there is continuity between all componnents. I have removed de caps and the resistor just in case, and I have cleaned pads and measure the value of R45. Everything is fine, but the issue is still there.

[oyanliz]

There is one thing that all the cards have in common. They had bad connection between edge connector pad and pcb track. Some cards came with edge connectors soldered when I bought the console. I checked all the 82E13 cards with this issue and in some cases, I resoldered the edge connectors area. There are a few cards working fine with already this repair done, but maybe those three cards... have any issue coming from there? I post this information, just in case.

I am thinking on removing all the components from one card, test all the tracks and components and place them back after checking the values.

Thanks once more.

Regards

Oihan

[oyanliz]

Hi,

I finally have found the issue on all the cards.

The VCA 82E13 cards with lower signal can fail because of the broken track of the pcb up side wich connects the C1 capacitor with R16 resistor. I have been checking voltage readings one mor time and I found the issue.

The VCA card with the issue of "overload led, lighting all the time" had the R45 (2.7Kohm) dead (thank you Anthony for your comment regarding to this typical failure.

I have all the VCA cards working fine now!!

Best regards.

Oihan

[horizonsound]

Great to know you got this sorted out.
I believe the later revisions moved the problem capacitors away from the 2.7k resistors.
Of the channels I had, about 4 of the 10 had this issue. (OL led always on)
E series from 1985.

Anthony.