Maxtrac board hieroglyphics

[sataraid1]

I've been inside so many Maxtracs I couldn't count them all, and I've always wondered about the markings that have been drawn inside them. The marks across screw heads are pretty easy to figure out, but there's always X marks, checks, black or red sharpie across the tops of certain components, and whatnot. Sometimes even the blobs of glue on the crystals or transistors are marked. Is there any rhyme or reason to these marks, or are they purely up to the whims and habits of the people who have built or worked on them?

What interests me most is when I see a particular component traced in red on the back of a board. I see this fairly often on the board interconnect, and occasionally tracing the cover of the VCO. Sometimes the big blobs of flux are a dead giveaway, but other times the solders don't appear to have been altered in any way.

Are these red marks indicative of components that have been repaired/replaced? Or perhaps didn't pass initial QC and went back for an "adjustment"?

What finally prompted me to ask is that I saw some logic boards listed as NOS, but they clearly have some of the red marks on the front and back sides of the board. I'd like to know if they could in fact be new, or have simply been pulled from radios for parts.

But mostly, I'm just curious.

[RFguy]

I always assumed they were marks made by the people assembling and testing them marking completion of different stages.