PET 2001 Fix....WAS: Will pay good money for NON working PET 2001 motherboard.

From: Philip Lord <>
Date: Mon, 09 Nov 2009 22:53:27 +0900
Message-id: <>
Thanks for your advice. I'll look into the cassette transistors after  
I figure out the character issue.
I also came across a page by Dave Gostelow that shows some pictures of  
his keyboard dismantling which will also help when I get around to  
fixing the keyboard.

I had only a few spare moments this evening to probe around the  
Character ROM, so I though I'd post the results in the hopes that it  
may help someone help me ;-)
Firstly, let me start by saying my logic probe is totally crap, and  
I've been meaning to get a good one.
The ROM adaptor I previously spoke about made it quite difficult to  
actually get to the pins of the 6540 socket, so instead I probed the  
2316 that was mounted to the top. Here are the results:

Seems that all the inputs are pulsing except 9 and 10 which are at 0V.  
All the outputs seem to be at 0V.
I downloaded the 2316 datasheet and looking that the truth table:

  if CE = Low, WE = Hi and OE = Low, then the mode is READ, Output is  
ACTIVE, and power is ACTIVE.

Unfortunately I don't actually know what all that means :-(

Thanks again

On Nov 9, 2009, at 2:39 AM, William Levak wrote:

> On Sun, 8 Nov 2009, Philip Lord wrote:
>> Hi William,
>> Thanks for he reply.
>> For my own education, I was wondering why you feel the the  
>> transistors are the issue?
> Experience!
>> I'm also wondering how exactly would you test for a short in a  
>> transistor??? Is that something that can be done in circuit  with a  
>> multimeter?>
> Since it causes the computer to hang up, you want to check for any  
> changes other than putting power on the cassette motor line.  I once  
> found one that had a short between two traces on the circuit board.
>> I'll take your advice on dismantling the keyboard and cleaning with  
>> alcohol. I'll need to be especially careful as this keyboard is  
>> actually a Japanese variant with Japanese characters also printed  
>> on the keys.
> Cleaning the keyboard contacts involves removing the keyboard from  
> the computer and removing the back of the keyboard.  It does not  
> involve the front of the keyboard at all.
> SDF Public Access UNIX System -
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Received on 2009-11-09 14:00:04

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