Amstrad 3in drive spares

Tony Duell ard at p850ug1.demon.co.uk
Tue Nov 2 15:30:07 CDT 2010


> Cheers for the link. Now I just need to fix the PCB on the 231 (some 
> idiot has gone and ripped a few tracks and pads off the board) and steal 
> some parts (a PCB mounting screw!) from the 156...

Is there soemthing special about the screw? Why do you need to take it 
from another drirve?

> 
> Given its wiring, I suspect SW1 is the drive select switch (it isn't 
> fitted on either of my drives). What I don't get is why it's got three 
> pins plus common. Common goes to the "SELECT" input on the controller 
> chip, 1 goes to /SEL1 (pin 4), 2 apparently goes to /SEL0, and 3 carries 
> the READY signal from the drive (?!). JP1 allows SEL0 and SELECT to be 
> bridged without the switch present.
> The only way this would make sense is if switch pin 3 was open-circuit...

The schematic I have to hand shows SW1 as switching bwtween drive select 
0 (pin 4 of the connecotr) and drive sleect 1 (pin 6 of the connector. 
The common connection goes to the D-SELCT/ input of the main ASIC. There 
is indeed a jumper to connect up Drive Select 0 if the switch isn't fitted.

Alas the manual doesn't show PCB layouts, just a schematic  So I have no 
idea if there's an exta non-connected pin on the switch.

-tony



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