Missile Command Help Needed.

Hi all I recently picked up a nice Missile Command and yup you guessed it it
does not work. In self test mode I get 6 long beeps and a short beep
followed by one long beep again. this is supposed to tell me there is a ram
error at location H4 if I am reading this right. OK fine I have no
TMS4116-20LN Chips.
Could anyone spare a few so I might try and get this one working again?

I was able to play a really short game before it went all wacky so I know
there is hope. Symptoms are coin mec clicking wildly garbled graphics and a
few wierd sounds when it is acting up. repetedly fiddeling with the slam
switch will eventually get it to boot properly and play again for a short
time but then it goes back to what I have described. Hoping for an easy
board fix but... well we all know how often that happens.

Thanks Darren A.