Resistor value on schematic shown as "S.A.T" What does it stand for please?

[Chris Wilson]

Reading a schematic for an EIP frequency counter a resistor is shown as 2%  S.A.T   It might be 5.A.T  Can anyone tell me what it stands for please?

Schematic attached, resistor outlined in pink. Thanks

[Smokey]

Not sure what that means, but there is usually another page somewhere that has a table of reference designators, values, and package sizes.  You might want to look up the number there.

[Fraser]

I believe this is the same as "Select on Test" (S.O.T), likely 'Select At Test'.

This is a component whose value is chosen during testing using a substitution box or resistors. It's a 2% tolerance part so the exact value is likely important to the operation of the circuit in which it operates.

From the circuit it would appear that this resistor works with R122 at the Mixer 1 LO input to set a DC level at that point.


Fraser

[Chris Wilson]

That might figure as I am having trouble with region of the circuit, maybe a biasing issue. If I warm Q12 the counter works on a particular range. I changed it for a brand new one with the same issue. I believe Q12 itself is fine, but warming it *may* alter its biasing needs, perfectly normally? If I measure the collector voltage referenced to ground I see 0.22 volts. If I warm Q12 even slightly I get a slowly, smoothly rising voltage, collector to ground, and at about .52V the counter starts reading on Band 2. Continue to warm Q12 (within very conservative bounds, not mad hot ), I see up to 11.9V.

As Q12 is allowed to cool to ambient the collector to ground voltage drops smoothly and slowly again, at around 0.5V the counter stops seeing the 10MHz input at 50mV, and reads zeros again. By the time Q12 is back to ambient I see 0.22V again. I am admittedly out of my depth, but feel the problem is local to this section of the circuit.

Base V is about 11.66V  Emitter V is about 12.07V

[w2aew]

Fraser has it right - S.A.T. means "Select At Test" - a value was adjusted/chosen at the end of the manufacturing line to make the circuit perform properly.  Usually this is done where a trimmer won't do, due to physical or performance reasons...

[Chris Wilson]

Thanks for the info.