[Coco] Disto 2 Meg kit

[Gene Heskett]

Robert Gault wrote:
> Bob Devries wrote:
>> Does anyone here have technical knowledge of the Disto 2 Meg kit?
>>
>> I want to put one into an Australian Coco3, but there's some 
>> differences in the components with respect to the 2 Meg kit.
>>
>> 1. The wire that should go to C60 connects to the junction between a 
>> resistor and the 28.63636 MHz crystal. The resistor connects to pin 2 
>> of the GIME chip. In the Australian Coco3, that capacitor connects 
>> directly to pin 2 of the GIME, and the crystal is 28.475 MHz. The 
>> crystel is actually one of those oven type devices in a larger metal 
>> case.
> 
> The circuit diagram in my service manual has C60 connected to pin 14 on 
> the crystal and +5v. Pin 8 of the crystal goes to GIME pin 2. Could be 
> the manual is wrong, but if it is right I'd think the wire should go to 
> GIME pin 2 not the cap.
> 
> Best bet would be to put a scope on pin 2 and see if the Disto wire 
> degrades the clock waveform. The only thing that could happen would be 
> that the Coco would not work and the scope would indicate a degraded 
> master clock signal.
> 
>>
>> 2. The other wire connects to HSYNC (pin 40 of IC5), which is the same 
>> as the Australian Coco3, but the HSYNC pulse is at a different rate to 
>> the US version.
>>
> 
> I'd just connect this up and see what happens. Can't do any harm.
> 
That would be my suggestion also.  As far as schematic differences, Tony 
NEVER shipped an accurate schematic, he was like a cartographer in that 
there were mistakes in every piece of paper he shipped just to throw the 
copycats off the trail.  So when you run into something that doesn't 
seem to be quite right, it probably isn't as the schematic shows if you 
actually trace out the pcb's.

-- 
Cheers, Gene