I also noticed that C1220 looks like it's got electrolyte squeezing>out of the end of it, and thought it was unrelated right now.
>However, now that I found it on the horizontal amplifier schematic, I
>see that its two connections are to -8V through R1220, and ground. So
>if that's shorted..
That cap is/was a common problem already when the 465 was quite young as early as 1976.
Normally when it shorted R1220 (22.1 ohm) went up in smoke although from your picture
yours look healthy so maybe the cap isn't shorted just leaky.
Here's what the internal Service Bulletin (Wizard's Workshop) said in 1980 making the replacement
of C1220 mandatory:
//465, REPLACE C1220 IN UNITS BELOW B294620
Reference: Wizard's Workshop, May 7 and December 22, 1976
C1220 has had three different part numbers during the life of the 465.
B010100 - B291513: 290-0550-00,1000uF, 10V
B291514 - B294619: 290-0759-00, 290uF,15V
B294620 & Up: 290-0807-00, 1000uF, 10V
P/N 290-0650-00 was removed because of a high failure rate (shorting).
P/N 290-0759-00 caused horizontal modulation when used with 50 hertz line power.
All 465 units below S/N B294620 should have C1220 in the Horizontal Amplifier
replaced with P/N 290-0807-00 if it still has an old type capacitor
Internationally manufactured units with the old part numbers would have been
shipped prior to January, 1977.
Roy L Apr.4, 1980