So I collect plugins for 500 series Tektronix scopes. One of those plugins is a 1GHz sampler called the 1S1.
Last week I discovered that the 1S1 actually uses embedded components in the PCB itself.
This isn't mentioned in the 1S1 manual, but if you look at the input to the sampling bridge (R4 R5 C4 C5) and look up the Tek part numbers, they are odd.
There is a Tek document that does mention these parts.
http://w140.com/tekwiki/images/f/f7/Tek_1s1_field_training_package.pdf"The circular pellet parts are inserted in the board before plating.
They are bonded into the board and then plated over. The board is then
etched in the usual manner, leaving the location of the parts practically
invisible to the eye"
Wow. Now I never looked that closely at the PCB to notice that certain parts aren't there, since the failures were always further down the signal chain.
Googling for "pellet parts" doesn't yield much except for pellet stoves and pet food pellets.
What could these parts be? Something like a 0402 part inserted into an unplated hole which is then plugged with conductive filler and plated over? Capacitors to ground I could picture, but how do you embed a series resistor into a trace?
This obviously wasn't beyond 1960s tech, but I've never heard of them used in 1960s Tektronix stuff. The faster plugins like the 1S2 don't mention it either but now I have to find out!
I have an itch to completely strip a 1S1 apart, removing the PCB from the chassis and seeing what my naked eye can't see.
The closest thing I saw was what's called "leadless" capacitors which are just a stack of dielectric with electrodes soldered directly to the board.