The ARP Pro Soloist introduced in 1972 and continued through 1981 as the Pro/DGX featured selectable presets, which used 8 archaic ROM chips to control the routing of the signal path (filter resonance, vibrato, ADSR parameters, etc). The ROM chip used was an Intersil IM5600, a 256 bit (!!) ROM that is long obsolete, and for which no compatible programmers are available today.
It has been long standing in the synth community that the ROMs are irreplaceable–once they go bad, one must be taken from another synth or the patient must be scrapped for parts. This is no longer the case, Synthchaser has replacements available. Contact us if you are in need of a replacement Pro Soloist or Pro/DGX ROM.
Update: ROMs may now be ordered in the Synthchaser store: