Re: C128 'VIC tower' mod board

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Thu, 9 Jul 2020 17:13:47 +0200 Message-ID: <07859c78-ba08-c634-97bd-bf62e377e775_at_laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

On 7/9/20 3:44 PM, Jeffrey Birt wrote:
> Hi all,
> 
> I pulled apart a C128 yesterday that someone sent in with a black screen 
> complaint. Upon investigating I found a small PCB with a 74LS74 perched 
> over top of U29 inside the VIC-2 RF shield box. I toned out how it was 
> wired and discovered it was intercepting /CAS. I posted this on a FB 
> group last night and someone said, ‘that looks like the VIC tower on 
> schematic sheet 310378-4. Sure enough he was correct.
> 
> http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c128/310378-4-left.gif

According to the schematics it's intercepting /RAS though.

It would be interesting to watch /RAS before and after the extra circuit 
on the scope to see what kind of difference it makes.

  Gerrit