Vintage Synth Repair

You want to look for surplus part vendors.  The one I've used in the 
past, Great Plains Electronics, has many obsolete memory parts, most 
older than the one you're searching, but had none of the parts you were 
looking for.

http://www.greatplainselectronics.com/default.asp

Scott Nordlund wrote:
> This is a (drastic) modification rather than a repair, so it's not a 
> stock part.  The stock part is a 21256 256K x 1 bit DRAM, and I am 
> attempting to replace it with a larger SRAM (with latches to separate 
> the row and column addresses and a banana jack patch bay to make all 
> address lines available for arbitrary rearrangement).
>
> I have several part numbers that I'm looking for- NEC UPD444001 or 
> UPD434001, Hitachi HM621400H, Toshiba TC551402J, and maybe (haven't 
> found a datasheet to confirm) Mitsubisihi M5M54R01.  DIP package would 
> be nice, but probably I'll have to settle for SOJ-32.  Any variant on 
> these would work as long as it's 5V and big enough to be soldered by 
> hand.  The speed rating isn't important (as the original chip is 
> considerably slower).
>
> There is a smaller (1M) and rather expensive chip available from 
> Digikey, and I can settle for this if necessary, but it won't be quite 
> as amazing as a 4M chip.  I have also found a 16M 3.3V chip.  The 
> biggest problem here is finding a 54 pin TSOP-II to DIP adapter for a 
> sane price.

-- 
John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com