2148h ram replacement

[stevebm1]

I have a commando bootleg that has a damaged 2148h ram chip,can I use a 2114 or 4464 ram chip in it's place?,as that is the only ram I have spare without ordering some new

 

[Georgian2]

Plug in the 2114. Most likely it won't work properly because it is a lot slower than the 2148.
4464 is dram. Different pinout and tehnology.

 

[stevebm1]

thanks for the reply,I have seen some AMD 2148-45dc on ebay ,not sure these are suitable replacements for the original NMC2148HJ-3 though?

 

[sukhbir]

The original may be 300ns,but to be clear you need to check the datasheet.
Slower rams will cause problems.

 

[Mc-Q]

thats a fast ramchip - probably 30ns not 300

 

[sukhbir]

Hi, can you tell me what is the original damaged ram chip type.

 

[sukhbir]

if it’s the first picture you have shown then it’s speed is 55ns.you need a ram that is 55ns or faster’

 

[stevebm1]

it,s the one in the picture above,the board boots to garbage,I inspected the board and found that the ram chip in the photo is missing 2 legs,so needs replacing,it might not be the only problem,but it definately needs replacing to start

 

[Mc-Q]

they are 4bit so usually used in pairs - check the other once incase it's in the same condition

 

[stevebm1]

replaced the ram chip,and the board sprung into life,but I have no sprites at all,so more issues to look into when I get some more spare time.

 

[TheDaddy]

Done a few of these , Try Removed clean and re fit ribbon cables.

Dave.

 

[stevebm1]

yeah the ribbon cables look pretty shot to be honest,can you still buy kits to replace them?,I know you used to be able to years ago

 

[TheDaddy]

Never tried , Possible I suppose. Mine are not great have to waggle them to get sprites back sometimes.

Dave.

 

[Mc-Q]

why would anybody buy the cables?
they are cheap to make - all you need is a pair of stout scissors and a crimp-tool or vice.

 

[stevebm1]

Do you have any links where to buy?

 

[Mc-Q]

cheapest places to check for plugs and cable would be CPC and Rapid Electronics