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

From: MikeS <>
Date: Wed, 15 Feb 2012 20:25:44 -0500
Message-ID: <0272B51169024671A8A71EACDBD4E317@vl420mt>
----- Original Message ----- 
From: "Rob Clarke" <>
To: <>
Sent: Wednesday, February 15, 2012 6:34 PM

> Q6) I think modern ATX supplies have now dropped the -12V rail. From
> looking at the schematics this is only used for the RS232 port. As I'm not
> likely to use this any time soon, will I have any issues if I omit
> the -12V rail?
AFAIK ATX supplies still supply -12V (blue wire, pin 14 of the 24-pin
version, pin 12 of the 20-pin version).

> 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?
As mentioned previously, an opto-isolator across the PS's AC input in series
with an appropriate resistor or capacitor to drop the voltage/limit the
current as required and a pull-up resistor if needed.

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Received on 2012-02-16 02:00:29

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