Vectrex ram replacement 2114 chips

[Shonman]

Hi,

 

I've recently discovered the joy of a Vectrex ownership, and have been trying to resurrect another machine which has issues. (I should add that I have minimal knowledge of electronics/computing/soldering etc. to guide me on my way)

 

The symptoms are that the display is corrupt i.e. broken lines jumping around, otherwise all is good.

 

I'm pretty sure the power board is ok having cross checked it with a working machine, none of the adjustments help, I have swapped over the socketed chips, checked for burnt components or bad solder joints, and replaced the caps on the logic board. Still no joy, same problem.

 

So I was thinking about replacing the soldered-in ram chips since I guess this could be a bit rot problem (?)

 

The installed chips are MCM2114-C30, which I believe are 300ns ones.

 

Could anybody tell me which 2114 chips would be compatible ? e.g. could I use MM2114N chips which are 450ns ?

Is the vectrex sensitive to the ram speed ?

 

Any advice appreciated, even just to tell me I'm barking up the wrong tree.

 

Regards,

 

J

[Rybags]

I'd guess no to 450ns chips.

 

Typically the access time needs to be under half a machine cycle.

 

e.g. Atari 8-bit 1.79 MHz, earlier machines recommended 250 ns RAM maximum access time. Half a machine cycle ~ 279 ns

 

Vectrex 1.5 MHz, half a machine cycle ~ 333 ns

[Rybags]

That RAM chip should be the same one C64 uses for it's Color RAM.

 

Fairly certain one of theirs would be suitable - C64 RAM needs to accomodate a 2 Mhz bus speed so will be more than quick enough.

[Shonman]

Thanks for the quick response.

 

I'll keep my eye out for non-working C64.

Not sure I've got the heart to dismantle a working one.

[Rybags]

A Google Search found someone with a similar question.

 

Jameco have them pretty cheap: http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDrillDownView?langId=-1&storeId=10001&catalogId=10001&freeText=2114&search_type=jamecoall

 

Additional to the earlier C64 info... they only have one chip anyway, so you'd need to scrap 2 machines.

Edited June 25, 2010 by Rybags

[sloopy]

i had to scrap a C64 for parts to fix my SX-64, i still have the color ram if you want it... might have a second one sitting around on my scrap boards, send me an IM if you are still looking for them...

 

 

sloopy.