[TenTec] PCB 90407?

[Shawn Upton]

Too hot to be outside, so poking around in this hamfest 505 find that I got last year(?).  The audio board had been reworked--so much so, no components were left of the audio strip!  I guess that's one way to debug, just remove and replace everything (except someone didn't get around to that).  For now I flew in an LM386 just to get by.
I've been poking around as to why it's got no RX and TX.  PTO is working, as is the 9MHz BFO.  The SSB generator board has been modified to take a Galaxy filter, and it's unknown if the 9MHz crystal matches it, but I'm just not there yet on that detail.  Right now I seem to get nothing out of the CA3053 mixer, so I'm working in that area.  Thing is, the 505 manual shows a 90191 board.  The one in this radio is marked 90407.  Looks really similar, but after a few hours of poking around, I came across a diode that looks factory under the mixer that is *not* on the 90191 schematic.  But the 509 manual, which shows a 80131 board, appears to be really similar to what I have.
Question: does anyone know what this 90407 is to?  Maybe it was a running change?  This looks like a low s/n 505, and the 505 manual that came with the radio isn't necessarily the one that came with the radio.
Thanks,Shawn kb1ckt