One other thing to check, make sure the can with the boards on the back of the tube is on straight and that there is no damage to those boards. When mine arrived from the ebay seller, that can was on squint (as you may be able to see from the above picture) suggesting the thing had been bounced around.
First thing I did was very carefully straighten everything up and check that none of the tracks on that board have been lifted.
The noise you are hearing could also be due to issues with the switch mode PSU glitching, so if you follow through my post on the badcaps site, you will see the parts I replaced on my PSU there. If you have an ESR meter then give all of the PSU caps the once over (pay particular attention to the caps I swapped as they are the most likely ones to fail).
Check the values of the resistors associated with the TDA4605 and the MOSFET.
If the switch mode controller circuit is not working correctly then the MOSFET may be overstressed or firing when not required, and this might also cause noise. (The usual warning about high voltages applies, there are some pretty hazardous voltages in that part of the world, and these persist for a while even after switching off and unpluging the mains lead).
Take care when replacing components, I found my board was very prone to tracks lifting. That may be because my de-soldering technique is a little rusty, but I'm blaming it on the fragility of the board. If reworking any of the TDA4605 stuff, carefully discharge the associated caps with a high value resistor before replacing the TDA4605 or the Mosfet, particularly the big 400V main input electrolytic (C11 - 100uF 400V on my version). Pay attention to the accuracy (1%) and wattage and voltage rating (500V plus, depending on the location) if changing any of the PSU resistors, use good quality low ESR high temperature replacement caps if you want the thing to still be working in 10 years time.
As I said previously, carefully remove as much dust as you can with a clean dry paintbrush. Dust + HT = horrible crackling noises, arcing leading to untimely demise. Many years ago I used to work with faulty CRT monitors and terminals a lot. The grubbier they were, the more likely they were to fail. Dust + airborne grease and grime can have a surprisingly low resistance.
I couldn't find the schematic for the PSU online, but there is a similar design here..
http://www.tvservice.org/files/img/n583_big.gif
Obviously there are differences in component values, layout, and so forth, but this is the closest TDA4605 based design I could find. Similar but different. Close enough for you to get an idea of how it works though.
If you do get a chance, see if you can get some clear sharp pictures of all of the boards in your scope (no need to take them out, but the pictures need to be clear enough to identify traces and chip markings). I have a feeling that it might be possible to do some interesting hacks on these things. My first target is trying to add a serial port. Next is to try to figure out how the digital card in the 8040, 8050, 8100 series does its magic.