Asteroids vector spot problem; nearly there?

[wreeve]

Hi all,
I've been luckily enough to purchase a very good condition Asteroids Cocktail; 1980 as you all know. This is going to be our living room coffee table so has to look nice!
Here are some photographs just how I got it home (it's been cleaned up since!)







Obviously dead on power up just hum from the speaker! The mains cord was in poor shape so was the first to be replaced. Looking over the boards and wiring they all looked in good condition. I ordered and replaced all the electrolytic caps just to be on the safe side.

Hopefully you can help me here:
Replaced so far:
Large blue cap. Looked OK to be honest.
All electrolytic caps on Audio / Regulator board. One was blown open circuit!
X/Y board in monitor. F300 found to be blown. Cause: one of the large capacitors failed. Replaced all caps and fuse. Unit powers up and fuses intact.
Cleaned all contacts
Checked for a clean 5v power on main game PCB. Regulator working fine!
Powered up and:
Problems:
Transformer hum. From the transformer; even with no load plugged in. Not loud but louder than I expected.
Sound. All the sounds that have played so far sound OK. But volume level low. When turned up the pot is noisy and there is hum through the speaker. Suspect volume pot?
Game play/graphics. Looks OK for as long as I have had the game on, less than 30 seconds! On closer inspect of the photo there seems to be a vector engine issue?
Monitor. The spot killer is active for about 10 seconds on power-up. Then the game appears but I have a couple of bright spots which are killing the monitor. See photographs. As you can see something isn't quote right with the graphics drive as text and asteroids have a spot in the middle! I wonder if this fault is monitor related of main board.





The spots...one has burnt the phosphor a little but not too much. There seems to be spots in the middle of the asteroids as well. Not good!
What I should have done from the start...but excitement got the better of me:





Spots visible on the oscilloscope. Looks like it's the vector circuit. Good news is the game plays OK and the buttons work! Need to fix the spots before I try the monitor again. Any trouble shooting pointers?
Any suggestions much appreciated guys (and gals?) please.

[Paladin]

Spot in the center and in the asteroids look to be the retrace lines.  They are visible when the brightness is turned up too high, and the center dot will burn through the phosphor, so don't leave it on very long like that.

Here's a good online Asteroids repair resource:
http://arcarc.xmission.com/Tech/Asteroid%20Tech/asteroidsrepair.html