[R-390] First R390A - let the adventure begin

[Larry H]

Tom,  Welcome to the R-390A world.  
It's quite common for the subchassis's to be swapped out over time, and you have an older one (1955), so even more so.  There were many different manufacturers of these units, so when referring to serial numbers, the manufacturer needs to be known.
There is a cap in the IF that can kill the mech filters, so it needs to be replaced with a very high quality 500 v or higher, BEFORE you power it up.  It's C553, and I think it's a good idea to test the leakage in the new replacement before you install it.  Any leakage is very bad.
Have to go - good luck.
Regards, Larry