Re: A newly working Commodore 720 - many questions...

From: MikeS <>
Date: Thu, 16 Feb 2012 11:09:13 -0500
Message-ID: <D38F3C0757194039B1D3D100767CF5E5@vl420mt>
----- Original Message ----- 
From: "Christian Dirks" <>
To: <>
Sent: Thursday, February 16, 2012 8:21 AM
Subject: Re: A newly working Commodore 720 - many questions...

>> Q7) The CBM-II PSU's all supply a 50/60hz signal from the PSU, which I 
>> think is just used for the TOD clock on the CIA. As I'm unlikely to find 
>> this on a modern PSU, is there a really simple way of generating this 
>> signal?
> Can simply be generated with a schmitt-trigger like in the c64.
> Take a look at the schematics at
> how the signal for the cia pin 19 is generated.
> For the schmitt-trigger (U23 in the schematics) a 74LS14 can be used.
Unless you can find 9VAC or some other low voltage line frequency AC signal 
in an ATX PS somewhere, I don't think an 'LS14 would withstand 110/220V very 
well... ;-) 

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Received on 2012-02-16 17:00:12

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