Working on a GE tube amp and I'm having trouble finding a replacement capacitor from the schematic I need a can with 40uf 450v 100uf 350v 40uf 350v any ideas on a source?

You can check with Hayseedhamfest or just use 3 separate capacitors.

To be on the safe side, use the highest voltage, as all the caps will be physically smaller and less expensive, I would think.
Here's one place, but there are a lot of supply companies.

https://www.tubesandmore.com/products/capacitors

I would suggest the vendors on the right side of the screen, they help support this site.

DM

The best and easist way to go is buy the individual caps in a RADIAL lead, install them directly under the old cap. You just solder onto the old negative (can shell )lugs and positive lugs, then snip the old lugs off the can and move the lug away. The leads are plenty strong to stay in place. NO unsoldering old leads ! No terminal strips ! FAST !!! EASY !!!! CHEAP !!!
Select modern radial caps that are the closest values. you can usually go UP 50% or more, and stay at or above the original voltage rating.
The caps I have for this would be two 47uf 450v and one 100uf 450v.

Some power supply designs are of the voltage doubler type. Select capacitors with a stated low equivalent series resistance (ESR) rating for that type of circuit. If other capacitor type is used, there may be a failure from overheating the capacitor or lower than required voltage output.

If there is no room underneath to add new caps, the other option would be to cut open the old cap, remove the innards, and install new ones inside gluing it back together

Just remember if you cut open the old can , dont ever use it as a handle again !

Good point Mark!

I guess it depends on how well the epoxy holds.

-Steve