(Question) 1990 Maxtor Terminator Resistors — #8

Post #8 by trag

Source Forum	68kMLA
Category	Hardware
Post Date	Wed, 14 Jan 2015 - 18:33
Original URL	https://68kmla.org/bb/threads/question-1990-maxtor-terminator-resistors.1040/

Post

max1zzz said:
I must be missing something here, in the dual 220/330 networks how could you messure 110ohms? surley buss from one pin you will get 330 and from the other 220?

I'm also sure I have pulled packs from drives that are 110 ohm bussed packs. But i'll go and double cheack that quickley..... Edit: just cheacked one and it was a simple 110 ohm bussed pack, my guess is that the drive it is from is using active termination and there is a 2.85v regulator connected to them

Look at the diagram in the pdf to which I posted the link. If you measure resistance from a pin to ground you do have a 330 ohm resistor to ground, but you also have a network of 8 550 resistors (220 + 330 in series) in parallel to ground in series with a 220 ohm resistor. Similarly from any pin to +5. Pin to pin it's 440 in parallel with 660.