Hi Oihan
No worries!
Its called PTFE Teflon Tube, you can get everywhere on the web, I buy the clear one and a couple of mm's thick. Its totally waterproof and it is NOT electrically conductive, so its the perfect solution to that problem.
Remember to clean the solder points very good with Isopropyl alcohol. The moisture underneath where the old heatshrink has been seated can be totaly rotten of coppershit, and makes everything short out! Clean clean clean!
Very important, check under the eq and group cards on the SSL mono channels, there is alot of headache underneath those two channel cards.
I have replaced all heatshrink in my center section and channels on my SSL 4048E.
Do yourself a big favor, and just replace the heatshrink on all center section cards.
When I turned on my console after install everything was just noisy, it was the moist heatshrink on the quad monitor card (card 25) causing that, I replaced the heatshrink with PTFE tube and then it was clean as a whistle!
There is ALOT of those "condoms" ind your SSL so do a close inspection of everything
Good luck with the board!
Best Regards Christian Heyman.