For example, if you want to buy an old floppy disk drive on ebay, always look for the termination resistor on the offer images. Often this is missing because the drive was used as the second drive. Here the termination resistor must be removed! Further information can also be found at Herb Johnson: Resistor termination for floppy data cables
Resistors with 150 ohms, as they are used in many old floppy disk drives, are now virtually no longer to buy. Below are two important product descriptions: Resistors Fa. Beckmann / Resistors Fa. Vishay (Dale)
With my TEAC drives FD-55A and FD-55F resistors of 330 Ohm and 1 Kilo Ohm can be used depending on the cable length. 330 Ohm for cables up to 3 m and 1 Kilo Ohm for cables up to 1.5 m in length.
Please pay attention, there are these resistors with 2x7 = 14 pins and with 2x8 = 16 pins! In addition, there are also floppys with separate resistors per line, e.g. with 220 + 330 ohms. In case of doubt always look into the documentation.
If a computer or flexible disk drive suddenly behaves strangely or makes strange sounds after a modification or expansion, check if the resistor is plugged in correctly. With two drives, only the last drive on the floppy cable has a resistor!