EE, I am trying to fix a circuit and have come across a group of axial capacitors with markings that I have had no luck deciphering. As best as I can tell, they are marked "BC 050" which doesn't follow any marking scheme I have been able to find.
They appear to go from pins on an IC to ground, if that helps. Here is a photo:
Please help me identify these!
Update:
The IC is MC68HC705JJ7, 20 pin DIP. The caps are connected to pins 1-4:
Pin 1: PB1/AN1 (IC side of cap has a parallel connection to a terminal for an external signal input)
Pin 2: PB2/AN2 (Appears to be nothing else on IC side)
Pin 3: PB3/AN3/TCAP (IC side has a parallel connection to a potentiometer)
Pin 4: PB4/AN4/TCMP/CMP1 (IC side is pretty busy, but appears to connect (through 2 series resistors) to an oscillator, and also pin 7 (non-inverting output) on a LM2904N amplifier…)
Best Answer
Those look like monolithic resin dipped ceramic capacitors. From your description of where they are they appear to be being used to stiffen the analog inputs against the S&H of the internal ADC. Given the adc is pretty slow (40-120ms a conversion), I'd guess they were 50nF.
With ceramics the first letter is usually the voltage rating, and the second letter is the temperature coefficient, then the value in PF. 050 would normally be 5pF but that seems very unlikely given their location. (also given a lowish voltage rating of B, you'd expect the capacitance to much larger given the package size).
Monores ceramics usually have terrible tolerances so tend to be used for decoupling, so are usually in the nF-uF range, so I suspect the 050 refers to a value in nF.