RE: testing RAM chips

>>What is the right way to check for defective RAM chips?
>
>The best thing to do here is check to see if the RAM will reliably save
>values written to it over time and with activity on the chip. Looking at
>the data bus alone will be tough because the bus can be fine-- you're really
>interested in the actual bits that are on the chip.
>
>The RAM test that a game board runs is a pretty good way to find a bad RAM.
>They usually do some bit patterns and whatnot at least. RAMs are best
>tested at full speed in the system they're used on-- removing and trying
>them on a cheap device tester often won't work. Also, RAMs can have
>peculiar failures. They can have sensitivity to patterns or certain areas
>being hit-- often sequential reads/writes will be fine but random
>read/writes will fail (and vice-versa).
>
>If you don't have a lot of time or tools, sometimes it's easiest to just
>pull the chip and plug in a replacement-- or swap it with another one on the
>board and see if the problem follows the chip.

The slef test showed the RAM at location M3 was faulty. This is also the first
Vector RAM tested, so therefore I figured it might as well be caused by the
vector data buffer or vector address decoder. Because the ROM can be accessed
(I can see text in the crosshatch screen (no crosshatch)) the address decoder
/ data bus looks fine (on the o'scope also).
I'll just desolder all the chips and swap them around to see if the problem
moves with the chip.

Regards,

Mendel

>-Clay
>________________________________________________________________________
>Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
>
>---------------------------------------------------------------------------
>** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
>** message body to vectorlist-request@synthcom.com. Please direct other
>** questions, comments, or problems to neil@synthcom.com.

---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.
Received on Tue Apr 25 04:09:20 2000