Leader 522 Oscilloscope repair advice

[Neuromodulator]

I bought this oscilloscope for $2, but after checking it out I noticed its got some issues. I'm fairly new to electronics, so I figured I could ask here for some help to figure out whats wrong. I noticed that there seems to be some compression/expansion issues across horizontal axis. It happens just in when the beam crosses the middle of the screen as you can see in the pictures. I also noticed that it happens on XY mode as much as in the sweeping mode, which makes me think the problem may be somewhere between the horizontal amplification and the crt. Its also interesting that when on XY mode plotting the same sine wave, depending on the frequency of the signal (in the pictures 1,000hz and 10,000hz) the artifact "behaves" different.

The scope is this one:
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Leader/LBO522%20&%20LBO523.pdf

 Any help or hint on how to fix it would be appreciated.
Thanks in advance

[poot36]

I would start by verifying the scope settings and after that check the voltages on the J5 and J6 connectors on the power supply board are within spec.  Don't forget to check for ripple on the power rails with a multimeter set to AC mode.  You should have less then 100mV of ripple if possable.

[tautech]

Service manual: http://www.eserviceinfo.com/downloadsm/28249/leader_lbo510-511.html

Ensure the PSU is correct FIRST.
PSU ripple specs in the schematic.

Then work through the troubleshooting charts.