Re[2]: Assistance please...

-----Original Message-----
From: Neil Bradley <neil@synthcom.com>
To: vectorlist@synthcom.com
Date: Mon, 30 Apr 2001 22:45:15 -0700 (PDT)
Subject: Re: VECTOR: Assistance please...

>
> > << I'm now completely baffled. Does anyone have any suggestions as to
> > where/how to start debugging this problem? I have all the parts I need to
> > continue my vector hack and I'd like to get it going again. >>
> > I'd socket & replace the 74LS245 @ F1 first.
>
> I think you meant the 74LS245 @ P1. F1 Is an EPROM socket.
>
> Man, I just don't know what the problem is. I wound up writing a program
> that just bangs 0ffh/00h to the entirety of vector RAM repeatedly. I've
> troubleshot for the last couple of hours and have done the following:
>
> * Swapped out all 2114s again just to make sure
> * Replaced the AMD 8304B with a 74LS245 (and yes, I soldered the socket
> down in the proper row of leads)
> * Verified that the DB lines were all toggling as expected (at the 245,
> the EPROM sockets, and the 2114s)
> * Verified that the AMxx lines were all toggling as expected (at all of
> the LS157s and both EPROM and 2214s)
> * Verified R/!W is reaching the 245 and is toggling
> * Verified !VMEM is present at every LS157
> * Verified that all of the AB0-AB12 lines were toggling out the side of
> all LS157s
> * Verified that the LS139 @ L2 keeps !VRAM low (since that's all my test
> does)
> * Verified that !VROM1/!VROM2 are always high (it's supposed to since I'm
> not accessing them)
> * Verified the 74LS32 @ M4 is giving toggled results as expected on both
> inputs and outputs
> * Verified the LS04 @ L4 is inverting as it should
> * Verified that !VRAM and M10 are making it to the 74LS32 and 74LS04
> respectively
>
> I did have one bad 2114 that stuck DB6 low, and another that stuck DB5
> low. Now that none stick, I've hooked back up the EPROMs and I still get
> the 2 high/1 low beep. ;-(
>
> Any suggestions at all? I'm not sure where to turn
 next!
>
> -->Neil
>

Try another 6502 cpu???

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Received on Tue May 1 20:44:35 2001