I'm currently repairing a device and I'm trying to understand what this circuit board does and how, and whether it is causing the malfunction. While doing that I stumbled upon this resistor whose color code does not agree with my multimeter. I'm measuring 152.1Ω, but the way I'm reading the colors it should be the very common value of 69.1MΩ. If I reverse the order, I get 1.51Ω/15.1GΩ/151GΩ, depending on whether the second color from the left is silver, grey or white. Black would give me 151Ω, but it definitely is not black.
The device this circuit board is from is pretty old. I don't know how old, but there is exactly one IC on it, with a datasheet published in April 1974. The relay in the background has 1979 written on it; I'm not sure if that is supposed to be a year.
Any ideas? Am I reading the colors wrong? Do I trust the multimeter or the markings regarding the intended value of this resistor? Have you seen resistors whose color codes have changed over decades of use?
Broken solder joints is a very good idea, thank you. I already found one earlier, but I haven't resoldered them all yet.
The relay is not performing as intended. The circuit board is controlling an electrolysis reactor which works fine until apparently the pressure switch decides the H2/O2 pressure is high enough and it tries to turn the reactor off. At that point the relay goes brrr, switching on and off very fast, producing a lot of sparks, and it stops when the fuse blows. Deactivating the pressure switch "fixes" the problem, but that is dangerous in itself.
Sorry for blowing up your thread but as for repairing it, might not hurt to draw up a schematic based on the board and try to ascertain exactly what the resistor is doing and why it is in the range it is in.
If it were me, I would separate out the pressure signaling system and see on which side the anomaly occurs. If you provide a solid signal and it still oscillates, the problem is probably in the main board. On the other hand, if a solid signal produces a one-off effect, the issue is in the pressure sensing module. Something is causing it to oscillate.
Thanks for your tips :) I already finished drawing the schematic, this resistor was the last part I hadn't clearly identified. Now I just need to understand it :D