I know what you have. It's either a TEC model TM-600 (19") or TM-623 (22" or 23"). Manuals should be at mikesarcade.com
The last address I had for TEC was this from 20 years ago:
TEC Videoelectronics, Inc.
3010 Scott Blvd.
Santa Clara, Calif. 95050
(408) 246-5428
I'm sure the area code has changed over the years.
Check the foil side for bad solder joints.
WARNING: This chassis is well known for suddenly catching fire!

Did I mention checking the solder joints?
I see that Bob Roberts has capkits for this chassis and I would strongly suggest getting that capkit pronto as some of the original caps actually catch fire. The replacement caps are much higher ratings so once you get those in you'll be ok.