I'm new to this site, you're my 1st reply!
If you still need repair help on that old Sony, I know what it is.
The "start-up" circuit on that chassis is complicated; 1 'lytic capacitor!
Your testing the old memory and it ain't what it use to be!
Here goes; the capacitor is a 10uF @ 160V or 250V on the PC Board directly under the CRT. Look at the schematic, it connects from raw B+ thru a resistor to the "+" side of the cap, the "--" side connects to the horiz osc B+ line. I think that was 12 or 18V. Totally simple, only 2 parts! Other makes used over a dozen parts to do the same thing!
It operates like this; when the set is 1st turned on, the raw B+ (150V I think) ramps up and the cap charges thru the resistor to the horiz osc B+ line. Since the cap is like a short circuit when not charged, that raw B+ is dumped thru the current limit resistor to bring up the horiz osc B+ close to normal. The horiz output circuit drives the HOT and the scan derived 18V supply takes over. The start-up cap charges and no current flows from it and the resistor anymore. Walla! Simple and effective!
I bought a KV-1710 from a Sony Dealer I worked at in 1974. We sold and serviced also. That's where I "fell-in-love" with Sony. My little Sister still uses that set in her Daughters' room to play games, etc. The set still looks brand new after 33 yrs. Instant on kept the CRT alive all these years!
Remember, 2 yrs later in '76, no more instant on! That TV won Sony an Emmy, the 1st time a TV got one! That was the most popular set of all times! It was on many commercials, TV episodes, talk shows. etc. That set was the 1st TV to make water look like water!
Anyway I'm rambling! Have fun and Happy Holidays... John