Re: IIgs frozen in time!

[Tristan Mumford <xtristan.xmumford@xgmail.xcom>]

glen herrmannsfeldt wrote:

> David Wilson wrote:
> 
>> On Sep 22, 10:15 am, Tristan Mumford <xtristan.xmumf...@xgmail.xcom>
>> wrote:
> 
>>>My main suspect is the clock xtal. Testing it is the biggest issue I
>>>have. I think I can get away with injecting a clock signal into the XIN
>>>pin of the clock chip briefly to see of the clock advances. Would this be
>>>destructive?
> 
>> I personally would not try feeding a signal into the XIN pin. Crystal
>> oscillator circuits would (I think) be fairly sensitive.
> 
> It is pretty common, especially with pins labeled XIN and XOUT to
> allow a signal from an external oscillator to the XIN pin.
> The exact voltage required would be system dependent, and I
> would be careful if I didn't know the voltage levels.

Agreed. The big issue would be figuring out a good way to create a low
enough voltage clock output. Horrific visions of using a voltage divider
made with high value variable resistors just went through my head. Perhaps
not the safest idea. Although we are working with a relatively low
frequency so a circuit not entirely unlike a headphone preamp / volume
control should allow the clock to go through at an arbitrary voltage.
I guess that would mean needing to dig out a transistor.

Anyway, thoughts please anyone?

Tristan.

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