WTB: (or scrounge) 4k x 4 SRAMS, 8168/6168/CY7C168/IMS1420P or equiv

[Chris Osborn]

I need to replace a couple of bad RAM chips on a Gauntlet board and
can't find any place on the internet to buy some. Need some IMS1420 or
8168 or equiv 4k x 4 srams to replace some bad RAM chips on a Gauntlet
board.

I was going through a stack of computer boards and looking for parts
but didn't see any (lots of 14.318 crystals on video cards
though). Anyone know if there's any old electronics I should keep an
eye out for that might have used these RAM chips? Does anyone have
some of these RAM chips they can sell me?

 

[[email protected]]

My recommendation is to contact this fellow at this email address.
Just remove the REMOVETHIS prior to emailing him.

[email protected]

 

[James Sweet]

I need to replace a couple of bad RAM chips on a Gauntlet board and
can't find any place on the internet to buy some. Need some IMS1420 or
8168 or equiv 4k x 4 srams to replace some bad RAM chips on a Gauntlet
board.

I was going through a stack of computer boards and looking for parts
but didn't see any (lots of 14.318 crystals on video cards
though). Anyone know if there's any old electronics I should keep an
eye out for that might have used these RAM chips? Does anyone have
some of these RAM chips they can sell me?

Did you try Google? I found this http://www.multigame.com/PARTS.HTM in about
3 seconds, there's a bunch more links so you may be able to get a better
price.

 

[Chris Osborn]

Did you try Google? I found this http://www.multigame.com/PARTS.HTM in about
3 seconds, there's a bunch more links so you may be able to get a better
price.

Yah I he doesn't have any, and all the other links are requests for
quotes with $100 minimum and/or just lists of data sheets.

 

[Franc Zabkar]

Yah I he doesn't have any, and all the other links are requests for
quotes with $100 minimum and/or just lists of data sheets.

I can't help you with the chips, but what I do in these cases is
replace the entire bank of RAM or ROM with a single high capacity
chip. For example, let's say your Gauntlet PCB has 16 chips organised
as 32K x 8. Then you could replace them all with just the one 61256 or
62256 32K x 8 SRAM. These are used as cache RAM in 486 motherboards. I
would remove the 16 chips (keeping them as spares?) and construct a
daughter PCB by wiring it to the address and data lines. If the chip
enables for each of the SRAMs are derived from a 1-of-8 decoder (eg
74LS138), then the high order address bits should be available there.

Of course this is just a hypothetical example, but if you have a
circuit diagram someone here should be able to help you with the real
thing.


- Franc Zabkar

 

[Franc Zabkar]

I can't help you with the chips, but what I do in these cases is
replace the entire bank of RAM or ROM with a single high capacity
chip.

Is the manual at this site the one for your machine?
http://basementarcade.com/arcade/library/manuals/g/

If so, then I would modify your PCB by removing the SRAMs at 6C-F,
6J-K, 7C-F, and 7J-K, and the 74S139 dual 1-of-4 decoder at 9C. I'd
replace the SRAMs with two 61256 32kx8 SRAMs (because they are
abundant and therefore cheap). One SRAM would be wired to the VRD0-7
data lines, the other to VRD8-15. Wire the RAM address lines, A0-A11,
to VRA0-11, and connect A12 to pins 2 & 14 of 9C, and A13 to pins 3 &
13 of 9C. Connect the CE* pins of the two SRAMs to pins 1 and 15 of
9C, respectively, and connect both OE* pins to the following circuit:

___ 74S00 ___
9C-3/13 ------| \ __| \
| |o----|__| |o-- OE*
9C-2/14 ------|___/ |___/



- Franc Zabkar