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First off as a moderator please put advise threads like this in the appropriate forum for the type of set being discussed, and not in the classifieds which are for buying and selling (now I have to move your thread to the rectangular Tube TV section).
Second: Some advice to calibrate your expectations. A tube color tv (as I suspect this is) is the most complex consumer electronic device predating home computers. If you want to DIY the repair, prepare to do a lot of research and detective work, and to find and make available technical info on the set. Many problems have a lot of potential causes that vary with the exact chassis design and shot gunning repairs (throwing parts at the wall hoping something will stick) usually harms more than helping.
It is generally best to have some experience doing capacitor replacement and general restoration on tube radios before thinking about tackling a TV.
If you plan to service it yourself you need to get the schematics for it. Look for the TV model and chassis number and search the sam's photofact index for it. You may need to post a want ad, but make sure you have the chassis number in the ad. (IIRC Chassis is more useful in maggies since some models were unique)
Since it probably has been dormant for a while measure the B+ voltages and compare to the schematic. If any B+ voltages are more than 30% off (especially if low) the power supply lytics may have gone bad from age/sitting dormant.
By no high voltage I assume you mean 25KV CRT voltage and not B+. Original tubes mean either a low hours set, or a high hours set that as not electronically maintained...In either case test them all on a good quality tube tester before digging in too far.
If B+ if good you can troubleshoot the horizontal. First make sure the horizontal output tube is not redplating (the plate of the tube should NOT glow in the dark, only the heater should). If the tube redplates it indicates one of several circuit faults and should not be run for more than 10 continuous seconds of plate glow....If ran longer the tube will be damaged and or have it's life shortened, also other rarer parts are put at risk.
If the tube is not red plating can you draw an arc from the outer winding of the flyback to the blade of an un-grounded, well insulated screw driver? If you get 1/2" or more of an arc but none at the CRT hv connector suspect a bad HV rect tube.
If there is no arc from the fly the next step is to measure the control grid and screen grid voltages on the Horizontal output tube and compare them against those listed on the schematic. Report back the results and we will help you interpret them.
If the grid is substantially less negative (more positive) than the schematic specifies then the H oscillator circuitry or it's coupling to the output is defective.
Troubleshooting is a game of comparing what is to what should be, knowing signal and power flow paths and where issues on them point to, then following that and repeating on a more detailed level until a defective part(s) is identified.
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