[TenTec] Scout 555 Question, no 2Mhz PTO signal

[Ben K8DIT]

My Scout quit working the other day. No power out. When dialing to the lower
part of the same band, I got power out. On the bench could not detect the
2Mhz. PTO signal that mixes with whichever band module happens to be plugged
in. So, is this the PTO failing? Or is it a PTO
component failing, like that buffer transistor on the PTO board? Or is it
something other?
I Checked for 5v. regulated at the obvious checkpoints with good results.
Does the front cover need to be removed for access? TIA Ben K8DIT