Re: Ribbon Cable

From: Gerrit Heitsch <>
Date: Tue, 17 Dec 2013 22:50:57 +0100
Message-ID: <>
On 12/17/2013 10:26 PM, wrote:
> On 2013-12-17, at 22:02, Gerrit Heitsch <> wrote:
>> Another detail I'd take a closer look at would be the 7406/pullup combo that tristates the output the 74LS257 multiplexers when it's VIC's turn. Replace it with a real driver (74LS04).
>>> That “nice” 180 on the OC output. Right - another interesting idea. It was probably a good (read: cheaper) solution and a good use for the otherwise unused 7406 gate.
>> Yes, and on the older boards R31 was 1KOhm and it still worked.
> Maybe less “usually” then ;-)

The switch from 1 KOhm to 180 Ohm happened on the 250407 board. I have 
some with R31 = 1 KOhm und some with R31 = 180 Ohm. Not sure what was 
changed to make that necessary. But all the boards work and pass all the 
tests I try.


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Received on 2013-12-17 22:03:51

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