While they are great scopes, many of the Tek 2200-series suffer from a tendency for the power supply to fail.
Luckily, they are usually easy to repair.
But first, you have to know how to stay SAFE when working on live high-voltage circuits! The following assumes that you can.
You will probably want and need a service manual for your scope, which contains all of the schematics and troubleshooting information.
After you figure out how to remove the case, first check the power supply voltages, which include +100, +30, +8.6, -8.6, and +5.
If any of them are off by more than 3% or so (I forget what the actual spec is, but some of yours will be way off if the power supply is down), then the first thing I would do is to find the discussions that are already on the web, where people went through diagnosing and repairing these power supplies in great detail. I have collected some of the better threads into text files that I can email you (PM me if you want them). But it is probably against the rules to post them here. You can find them yourself, though, as follows:
Find the TekScopes group, at yahoogroups.com and search its message archives for this exact title:
Tex 2213A - Power Supply Problems
Yes I know it says 2213A. But the power supply is identical in the 2215A, as it also is in the 2235, and probably others (except for the non-A 2213 and 2215, which didn't have the 43V pre-regulator circuitry).
Also go to
Google Groups and search the sci.electronics.repair group for this title:
Tek 2235 problem
Both groups also have other threads that deal with these power supplies. And after you get into the actual diagnosis of your scope, those groups have people who can be very helpful, including some ex-Tektronix technicians and engineers. (But remember to be polite, and always search before asking.)
If the power supply rails are NOT the problem, the first thing I'd check (besides "pilot error") is the wires that connect to the CRT tube (the single wires that connect to pins on the sides of the tube, not the ones going to the socket in the rear). Some of them had a habit of coming off the (deflection) pins, which kept the beam off the screen.
After that, there are lots of other reasons why you might get no display. But they are mostly pretty easy to diagnose and repair, in the 2200-series scopes.
Good luck,
Tom