Re: Assistance please...

This is where a Fluke 9010 comes in handy. Or a Cat Box....you need to try
writing "AA" and "55" to the RAM to see if the bits are stuck on any Data
lines.

I have found that 2114's a sometimes fussy, have you tried moving them
around to see if the tone sequence changes? I have had problems with Vector
Ram that was related to poor chip select drives as well.

John :-#)#

At 10:45 PM 4/30/2001 -0700, you wrote:
> > << 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
>
>-------------------------------------------------------------------------------
>Neil Bradley Play a song wrong once and it's a mistake.
>Synthcom Systems, Inc. Play a song wrong twice and it's Jazz.
>ICQ #29402898
>
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Received on Mon Apr 30 23:03:16 2001