This majestic old mixing console had started to show it’s old age. Master section wasn’t working anymore and some input channels were popping/farting and some didn’t pass signal anymore. After consulting Soundtracs-guru Tim @ Studiosystems for schematics and troubleshooting info I started looking for bad capacitors in the master section…and indeed there was plenty of them. We decided to do a full recap on the master section since the desk is so old. First I did a cleanup on the circuit board and IC sockets and got to work.
Hardest part of recapping is taking the old parts out. You have to be very careful when pulling out the old caps because the circuit board traces lift up very easily! Use a solder wick to remove ALL old solder first and then pull the cap gently with fingers/pliers and heat up the traces lightly from the other side. Even though I was very careful doing this some traces lifted up and I had to use jumpers to get the connections working. For capacitor replacements I used Panasonic FC/FM series and some nice Nichicon audio series caps (Low ESR).
When master section was recapped we tested the desk and there was sound… :) Noise floor was incredibly low and sound was clean and punchy! Moving on to the input channels…
Because of the vast number of input channels we did full recaps only to the non-functioning modules. To weed out bad caps from the rest of the glitchy channels I used an excellent tool called ESR meter from EVB (Thanks Vitor for the fast delivery!). You can read more info from his webpage. I ordered mine pre-assembled and calibrated. Oh man I wish I had gotten this tool earlier…finding bad caps is so fast and easy with this one! You can measure them IN CIRCUIT. I highly recommend this tool for everyone who has to troubleshoot circuits!