[Bill Cahill]

First, without the yoke, you can't get hv.
Secondly, the correct horiz. freq. on these sets is 15,750.
Yours sounds very low.
The 5U4 is quite capable of getting up the proper voltage as long as the tube is good. And, a tube tester claiming it's good means very little.
If the getter on horiz. out. has changed from clear, it's likely gassy. Not a good thing.
Blue glow on aud. out. is gas. Also not good.
The micas in these sets tend to get leaky, and, will cause nasty things in picture.
In the horiz. the oscilator will not run on correct frequency, and, could have a hunting problem.
In sync circuit, it will make both the vertical, and, horiz. un stable.

Which chassis is this?
Does it have the 6J5 vertical oscilator, or, the 6SN7 vertical oscilator-sync seperator?
If it is the later more deluxe set, there are other things you need to know that sams doesn't include.
The tube chart in cabinet will help there.
Also, if there is a 3 lug terminal strip screwed to the side of chassis near vert. oscilator, it's the more deluxe chassis. They primarily use it with a capacitor going to it.
It's a coupling cap not used on cheaper chassis.

There is a 100 ohm two watt resistor on horiz. out. Cathode that will likely need replacement, as well. They take alot of current, and, tend to cook, causing them to go 50-100 percent high.
That will also affect your hv.
Bill C.