This post is from quite some time ago but this may be of interest when fixing some older tek scopes. I have not managed to find any schematics for older tek scopes that I own but to my surprise, when I was fixing an old 500 Mhz Lecroy scope and a TDS460A 400 Mhz scope recently. I found the PSU PCB`s looked very similar, It turns out that both supplies were made by "power systems inc".
I needed to find out if a custom component was still available so I tried to contact the company behind the supply, after some research I found that they had been bought over in the 90`s by a large company and then liquidated in 2003
. After some further research I found that there was a few lecroy service manuals available which had very poor scans of the schematic on the power supply side. If found two different schematics which were very similar to the Tek supply but not exactly the same, although not the same, these schematics did help me figure out how the supply worked and what the problem was on both supplies I had.